investigation of the nutritional requirements ...in fulfillment of the requirements for the degree...

INVESTIGATION OF THE NUTRITIONAL

REQUIREMENTS OF AUSTRALIAN SNAPPER

PAGRUS AURATUS (BLOCH & SCHNEIDER, 1801)

A thesis presented by

Mark Anthony Booth BSc (Hons)

to the

School of Life Sciences

Queensland University of Technology

In fulfillment of the requirements for the degree of

Doctor of Philosophy

October 2005

I

ABSTRACT

This thesis describes research designed to increase our knowledge of the

nutritional requirements of Australian snapper Pagrus auratus and provide information

on the potential of Australian feed ingredients to reduce the level of fishmeal in diets

for this species.

The apparent digestibility of organic matter (OM), crude protein (CP), crude fat

(CF) and gross energy (GE) from selected animal, cereal or oilseed meals incorporated

at different inclusion levels was determined. Snapper were extremely efficient at

digesting the CP, CF and GE from fishmeal and rendered animal meals (range 80-

100%) with the exception of meat meal, where CP and GE digestibility were lower (62-

65%). The CP from oilseeds was better digested (87-91%) than OM (57%) or GE (64-

67%). Digestibility of nutrients and GE from animal meals and fish oil was not

influenced by inclusion level. The CP from extruded wheat was highly digestible (100-

105%), but, the OM, CF and GE digestibility of extruded wheat declined as inclusion

levels increased.

The interactive effects of inclusion level (150, 250, 350 or 450 g kg-1) and fish

size (110 vs 375 g snapper) on the apparent digestibility of OM and GE from

gelatinised wheat starch were investigated. The OM and GE digestibility of gelatinised

wheat starch was high (89%) at low inclusion levels, but declined significantly in both

fish sizes as the level of starch increased. There was no interaction between inclusion

level and size of fish and the decline in GE digestibility could be predicted by the

regression; GEADC = 104.97(±3.39) – 0.109(±0.010) x inclusion level (R2=0.86). Larger

fish were more capable of digesting the GE from gelatinised starch than smaller fish.

Regardless of fish size, short and longer-term changes in the physiology of

snapper fed or injected with carbohydrates were recorded. Liver and tissue glycogen

concentrations and the hepatosomatic index (HSI) of snapper fed gelatinised starch

were significantly elevated. The plasma glucose concentrations of fish injected intra-

peritoneally with D-glucose increased from resting levels (0.4–4.6 mM) to 18.9 mM

approximately 3 hours after injection and fish displayed a hyperglycaemic response for

nearly 18 hours. In contrast, the post-prandial response to the uptake of glucose from

normally digested gelatinised starch was more regulated.

A dose-response study to determine the effects of digestible energy (DE)

content (15, 18 or 21 MJ kg-1) on the digestible protein (DP) requirements of juvenile

II

snapper was assessed using a four parameter mathematical model for physiological

responses (4-SKM). DP content of test diets ranged from 210 to 560 g kg-1. Weight

gain and protein deposition was strongly dependent on the ratio of DP:DE. According

to the fitted models, diets for snapper weighing between 30–90 g and reared at

temperatures ranging from 20-25ºC should contain a minimum of 28 g DP MJ DE-1 to

promote optimal weight gain and protein deposition.

The effect of varying the absolute content of DP and DE on the weight gain

and performance of snapper (100-300 g) fed diets formulated with an optimal ratio of

DP:DE was investigated. In addition, non-protein sources of DE were varied by

adjusting the ratio of fish oil to gelatinised wheat starch in order to determine if

different ratios of these ingredients affected performance. High-energy diets (22-23 MJ

DE kg-1) suppressed feed intake, but provided DP intake was not limited by feed intake,

maximum weight gain was approached. Lower-energy, lower-protien diets (15-18 MJ

DE & 315-390 DP) encouraged higher feed intake but DP intake was restricted, which

reduced growth potential. Snapper performed best on high-energy, high-protein diets

(490 DP & 21 MJ DE), provided a significant proportion of DE was supplied as DP.

Fish oil and pregelatinised wheat starch could be interchanged according to their DE

values without unduly affecting fish performance in diets providing 390-490 g DP kg-1.

Two utilisation studies were undertaken to investigate the performance of

snapper fed diets containing increasing levels of poultry offal meal, meat meal and

soybean meal. All diets were formulated with similar DP and DE contents. Snapper

readily accepted feeds containing high levels of poultry meal (360 g kg-1), meat meal

(345 g kg-1) or soybean meal (420 g kg-1), before weight gain and performance was

negatively affected. In combination, these feed ingredients were able to replace all but

160 g fishmeal kg-1 in commercially extruded test feeds for this species.

The research described in this thesis has extended knowledge of the

nutritional requirements of Australian snapper by providing important information on

the digestibility of Australian feed ingredients. These coefficients have been integral in

formulating both experimental and semi-commercial test diets for snapper and will

increase both the accuracy and flexibility of commercial diet formulations for this

species. High performance feeds for snapper will contain high levels of DP, but must

provide a significant proportion of DE in the form of protein. These constraints can be

satisfied by using alternative, well-digested protein and energy sources that have the

potential to replace all but 160 g kg-1 fishmeal.

III

STATEMENT

I, Mark Anthony Booth, hereby declare that the work presented in this

thesis has never been previously submitted for a degree or diploma at any other

University. I also declare that to the best of my knowledge and belief, this thesis

contains no material previously published or written by another person, except where

due reference is made in the thesis itself.

Signed................................................

Mark Anthony Booth

Date 20th October 2005

V

ACKNOWLEDGEMENTS

I am greatly indebted to the following people for their help, support and

inspiration during my candidature. Firstly, special thanks to my industry supervisor Dr

Geoff Allan (Principal Aquaculture Research, NSW DPI Fisheries) for his enthusiasm,

encouragement and friendship. I will be forever grateful for his efforts in advancing my

knowledge of fish nutrition and fostering the development of my career. Special thanks

also go to my QUT supervisor Dr Alex Anderson (Senior Lecturer in Biochemistry,

School of Life Sciences, QUT) for his support, advice and friendship. As an off-

campus student, it was great to know I could always call upon him to untangle the

paperwork.

I would like to acknowledge the excellent technical assistance I have

received from the staff at NSW DPI Port Stephens Fisheries Centre (PSFC),

particularly Ian Russell, Ben Doolan, Peter Dickson, Joel Goodsell, Rebecca Warner-

Smith and Ian Campbell. In addition, I extend special thanks to Dr Stewart Fielder, Bill

Bardsley, Luke Cheviot, Paul Beevers and Deb Ballagh for supplying the snapper used

in my research. I am also indebted to NSW DPI Fisheries Research Scientists Dr

Wayne O’Connor, Dr Stewart Fielder and Dr John Nell for internal critical review of

the manuscripts presented in this thesis and Ms Helena Heasman and Ms Jo Pickles for

administrative support.

I would also like to acknowledge the FRDC and the Aquafin CRC for

Sustainable Aquaculture of Finfish for providing me with financial assistance to attend

CRC conferences within Australia and to attend several professional development

courses. In particular, I extend special thanks to Dr Chris Carter and Ms Emily

Downes.

The chemical analyses conducted throughout this study would not have been

possible without the expertise and cooperation of many people, especially Lynn Clarke

(HAPS), Tony Shorter (CSIRO), Robert Scurr (FALA), Heather Lindsay (SCL) and

staff at (SARDI).

I wish to acknowledge Dr L. Preston Mercer (University of South Florida,

USA) for his invaluable assistance with 4 parameter SKM and Dr Ingrid Lupatsch

(National Centre for Mariculture, Eilat, Israel) for review of data presented in Chapter

3. Thanks also to Dr Dannie Zarate (formerly Ridley Aqua-Feed Pty Ltd) for assistance

in the manufacture of extruded test diets compared in Chapter 6.

VI

To my parents Peggy and Tony and parents in-law Beverley and Reg, my

heartfelt appreciation for your love and support over the last few years, especially for

the extra care of my three sons. Your unselfish assistance has been integral in the

success of this and many other ventures.

To my dearest boys, Dylan, Jackson and Harrison, thankyou for putting up with

me when the stress of it all meant I was not always as pleasant as I should have been.

Finally and most importantly, to my wife Jodi. Thank you for your love, support

and understanding. Without you, none of this would have been possible. I doubt we

would have dreamed our lives could be blessed with so much.

VII

PUBLICATIONS ARISING OR EXPECTED FROM THIS THESIS

Refereed journals

Booth, M.A., Allan, G.L. & Anderson, A.J. (2005) Investigation of the nutritional

requirements of Australian snapper Pagrus auratus (Bloch & Schneider, 1801):

apparent digestibility of protein and energy sources. Aquaculture Research 36,

378-390.

Booth, M.A., Allan, G.L. & Anderson, A.J. (submitted) Investigation of the nutritional


effects of digestible energy content on utilisation of digestible protein.

Aquaculture Research.



weight gain and performance on diets providing an optimal ratio of digestible

protein:digestible energy, but different digestible protein and energy contents.


Booth, M.A., Anderson, A.J. & Allan, G.L. (in press) Investigation of the nutritional


digestibility of gelatinised wheat starch and clearance of an intra-peritoneal

injection of D-glucose. Aquaculture Research.



influence of poultry offal, meat or soybean meal inclusion level on weight gain

and protein retention. Aquaculture Research.

Presentations, abstracts or conferences

Allan, G.L & Booth, M. A. (2002) Replacing fishmeal in diets for an omnivore (silver

perch, Bidyanus bidyanus) and a carnivore (snapper, Pagrus auratus). In:

VIII

Program and Book of Abstracts from the 6th International Symposium on

Aquatic Nutrition. Convention Centre, Cancun, Quinanaroo, Mexico.

September 2-6, 2002. 163pp + 6 supp. pp. Oral presentation by Dr Geoff Allan.

Allan, G.L., Fielder, D.S., Booth, M.A., Pitt, P. & Lester, B. (2002) Increasing the

profitability of snapper Pagrus auratus farming by improving hatchery

practices and diets, CRC Project 2.3. Aquafin CRC Conference & Proceedings

2002, Wrest Point Convention Centre, Hobart, September 23, 2002. Abstract

and oral presentation by Mark Booth.

Booth, M.A. (2003) Formulation of practical diets for Australian snapper Pagrus

auratus. PhD Confirmation Seminar, Queensland University of Technology,

School of Biosciences, May 4, 2003. Oral presentation.

Booth, M.A. (2003) CRC snapper workshop 2002. In: Aquafin CRC Quarterly

Newsletter, AquaSplash Vol. 1 (3), June 2003. Short article by Mark Booth.

Booth, M.A., Allan, G.L. & Anderson, A.J. (2003) The effects of digestible protein and

energy content on the performance of juvenile Australian snapper Pagrus

auratus (Project 1B.3). Aquafin CRC Conference & Proceedings 2003, The

Lakes Resort Hotel, West Lakes, Adelaide, SA. October 27-29, 2003. Abstract

and oral presentation by Mark Booth.

Booth, M.A., Allan, G.L., Fielder, D.S. & Lester, B. (2003) Increasing the profitability

of snapper Pagrus auratus farming by improving hatchery practices and diets:

collaborative research between NSW Fisheries and the Aquafin CRC. In:

Expanding the Aquafeed Ingredient Base. Proceedings of the Second Annual

Aquaculture Nutrition Subprogram Workshop – Fremantle, WA. May 29, 2003

(Ed. R. van Barneveld). ANS Publication No. 1, June 2003. Conference

proceedings and oral presentation by Mark Booth.

Booth, M.A. & Allan, G.L. (2004) Aquaculture diet development: understanding the

relationships between feed ingredients and the nutrient requirements of fin-fish.

Australasian Aquaculture Conference - Profiting from Sustainability, September

IX

26-29, Sydney Convention Centre, NSW, Australia. Abstract and oral

presentation by Mark Booth.

Fielder, D.S., Booth, M.A. & Allan, G.L. (2003) Status of marine fish production in

NSW. In: Proceedings of the Aquafin CRC Snapper Workshop held on 26

September 2002 at the Airport Motel Convention Centre, Melbourne (Aquafin

CRC 2001/208) (Ed. G.L. Allan). NSW DPI Fisheries, Cronulla, NSW,

Australia. 7-19.

Other outputs related to snapper research during candidature

Allan, G.L. & Booth, M.A. (2005) Recent research on the use of rendered animal

proteins in diets for marine finfish in Australia. World Aquaculture Society,

Aquaculture Conference 2005, Bali, Nusa Dua, May 9-13, 2005. Abstract and

oral presentation by Dr Geoff Allan.

Booth, M.A., Warner-Smith, R.J., Allan, G.L. & Glencross, B.D. (2004) Effect of

dietary astaxanthin source and light manipulation on the skin colour of

Australian snapper Pagrus auratus (Bloch & Schneider, 1801). Aquaculture

Research 35, 458-464.

Doolan, B.J., Allan, G.L., Booth, M.A. & Jones, P.L. (2005) Improving skin colour in

farmed snapper (= red sea bream Pagrus auratus). World Aquaculture Society,

Aquaculture Conference 2005, Bali, Nusa Dua, May 9-13, 2005. Abstract and

oral presentation by Ben Doolan.

Tucker, B.J., Booth, M.A. & Allan, G.L. (2004) The effects of photoperiod and feeding

frequency on the performance of juvenile snapper. Australasian Aquaculture

Conference - Profiting from Sustainability, September 26-29, Sydney

Convention Centre, NSW, Australia. Oral presentation by Mark Booth.

XI

TABLE OF CONTENTS ABSTRACT......................................................................................................................I

STATEMENT................................................................................................................ III

ACKNOWLEDGEMENTS ............................................................................................ V

PUBLICATIONS ARISING OR EXPECTED FROM THIS THESIS....................... VII

Refereed journals ................................................................................................. VII

Presentations, abstracts or conferences................................................................ VII

Other outputs related to snapper research during candidature ...............................IX

TABLE OF CONTENTS...............................................................................................XI

LIST OF ABBREVIATIONS....................................................................................XVII

LIST OF FIGURES ....................................................................................................XIX

LIST OF TABLES ......................................................................................................XXI

CHAPTER 1. GENERAL INTRODUCTION.................................................................1

1.0 INTRODUCTION .................................................................................................3

1.1 Aquaculture: the world perspective ...................................................................3

1.2 Increased demand for compound aquafeeds: fishmeal and fish oil ...................4

1.3 Aquaculture: the Australian perspective ............................................................6

1.4 Marine finfish aquaculture in Australia .............................................................8

1.5 Potential of Australian snapper Pagrus auratus ................................................9

1.6 Current status of snapper culture: Japan ..........................................................10

1.7 Current status of snapper culture: Australia.....................................................11

1.8 Constraints to growth of Australian snapper industry .....................................13

1.9 Need for research .............................................................................................13

1.10 Digestibility and utilisation of feeds and feed ingredients.............................15

1.11 Scope and aims of study.................................................................................17

CHAPTER 2. APPARENT DIGESTIBILITY OF PROTEIN AND ENERGY

SOURCES......................................................................................................................19

2.1 ABSTRACT.........................................................................................................21

2.2 INTRODUCTION ...............................................................................................23

2.3 MATERIALS AND METHODS.........................................................................25

2.3.1 Diets ..............................................................................................................25

2.3.2 Facilities ........................................................................................................26

2.3.3 Fish................................................................................................................28

XII

2.3.4 Feeding and collection of faeces................................................................... 29

2.3.5 Chemical analyses......................................................................................... 29

2.3.6 Apparent digestibility calculations................................................................ 30

2.3.7 Statistical analyses ........................................................................................ 30

2.4 RESULTS ............................................................................................................ 33

2.5 DISCUSSION ...................................................................................................... 37

2.5.1 Digestibility of energy sources ..................................................................... 37

2.5.2 Digestibility of protein sources ..................................................................... 39

2.6 REFERENCES..................................................................................................... 43

CHAPTER 3. EFFECTS OF DIGESTIBLE ENERGY CONTENT ON UTILISATION

OF DIGESTIBLE PROTEIN......................................................................................... 49

3.1 ABSTRACT......................................................................................................... 51

3.2 INTRODUCTION ............................................................................................... 53

3.3 MATERIALS AND METHODS......................................................................... 55

3.3.1 Diet formulation............................................................................................ 55

3.3.2 Fish................................................................................................................ 57

3.3.3 Growth experiment ....................................................................................... 58

3.3.4 Performance based calculations .................................................................... 59

3.3.5 Digestibility experiment................................................................................ 60

3.3.6 Digestible nutrient calculations..................................................................... 61

3.3.7 Chemical analyses......................................................................................... 61

3.3.8 Statistical analyses and curve fitting............................................................. 62

3.4 RESULTS ............................................................................................................ 65

3.4.1 Effects of DP and DE on feed intake and growth ......................................... 65

3.4.2 Effects of DP and DE on carcass composition ............................................. 67

3.4.3 Curve fitting .................................................................................................. 67

3.5 DISCUSSION ...................................................................................................... 71

3.5.1 Requirements for maintenance and growth .................................................. 71

3.5.2 Effects of DP and DE on feed intake and feed conversion........................... 73

3.5.3 Effects of DP and DE on carcass composition ............................................. 75

3.5.4 Conclusion .................................................................................................... 75

3.6 REFERENCES..................................................................................................... 77

XIII

CHAPTER 4. WEIGHT GAIN AND PERFORMANCE ON DIETS PROVIDING AN

OPTIMAL RATIO OF DIGESTIBLE PROTEIN:DIGESTIBLE ENERGY, BUT

DIFFERENT DIGESTIBLE PROTEIN AND ENERGY CONTENTS. ......................81

4.1 ABSTRACT.........................................................................................................83

4.2 INTRODUCTION ...............................................................................................85

4.3 MATERIALS AND METHODS.........................................................................89

4.3.1 Experimental diets.........................................................................................89

4.3.2 Fish................................................................................................................90

4.3.3 Experimental facilities ..................................................................................92

4.3.4 Feeding..........................................................................................................92

4.3.5 Water quality.................................................................................................93

4.3.6 Chemical analyses.........................................................................................93

4.3.7 Statistical analyses ........................................................................................93

4.4 RESULTS ............................................................................................................95

4.5 DISCUSSION ......................................................................................................99

4.5.1 Weight gain and performance .......................................................................99

4.5.2 Effect of lipid and carbohydrate ratio on performance ...............................103

4.5.3 Conclusions.................................................................................................104

4.6 REFERENCES...................................................................................................105

CHAPTER 5. DIGESTIBILITY OF GELATINISED WHEAT STARCH AND

CLEARANCE OF AN INTRA-PERITONEAL INJECTION OF D-GLUCOSE ......109

5.1 ABSTRACT.......................................................................................................111

5.2 INTRODUCTION .............................................................................................113

5.3 MATERIALS AND METHODS.......................................................................115

5.3.1 Digestibility of pregelatinised wheat starch................................................115

5.3.2 Post-prandial plasma glucose, HSI and glycogen evaluations....................118

5.3.3 Chemical analyses.......................................................................................119

5.3.4 Acute glucose tolerance test........................................................................119

5.3.5 Water quality...............................................................................................120

5.3.6 Statistical analyses ......................................................................................121

5.4 RESULTS ..........................................................................................................123

5.5 DISCUSSION ....................................................................................................127

5.5.1 Digestibility of gelatinised starch ...............................................................127

XIV

5.5.2 HSI and glycogen concentration................................................................. 129

5.5.3 Glucose tolerance........................................................................................ 130

5.5.4 Conclusions................................................................................................. 132

5.6 REFERENCES................................................................................................... 133

CHAPTER 6. INFLUENCE OF POULTRY OFFAL MEAL, MEAT OR SOYBEAN

MEAL INCLUSION LEVEL ON WEIGHT GAIN AND PROTEIN RETENTION.139

6.1 ABSTRACT....................................................................................................... 141

6.2 INTRODUCTION ............................................................................................. 143

6.3 MATERIALS AND METHODS....................................................................... 145

6.3.1 Diets Experiment 1...................................................................................... 145

6.3.2 Diets Experiment 2...................................................................................... 147

6.3.3 Fish.............................................................................................................. 149

6.3.4 Facilities ...................................................................................................... 149

6.3.5 Water quality............................................................................................... 151

6.3.6 Chemical analyses....................................................................................... 151

6.3.7 Statistical analyses ...................................................................................... 152

6.4 RESULTS .......................................................................................................... 153

6.4.1 Experiment 1 ............................................................................................... 153

6.4.2 Experiment 2 ............................................................................................... 153

6.5 DISCUSSION .................................................................................................... 157

6.5.1 Effects of ingredients on utilisation ............................................................ 158

6.5.2 Effects of ingredients on diet palatability ................................................... 159

6.5.3 Effects of ingredients on physical characteristics of diets .......................... 160

6.5.4 Combinations of ingredients ....................................................................... 160

6.5.5 Conclusion .................................................................................................. 161

6.6 REFERENCES................................................................................................... 163

CHAPTER 7. GENERAL DISCUSSION AND CONCLUSIONS............................. 167

7.1 GENERAL DISCUSSION ................................................................................ 169

7.1.1 Importance of digestibility in nutrition research......................................... 169

7.1.2 Digestibility coefficients for snapper.......................................................... 170

7.1.3 Additivity of apparent digestibility coefficients for snapper ...................... 172

7.1.4 Application of digestibility coefficients...................................................... 173

XV

7.1.5 Estimating protein requirements .................................................................173

7.1.6 Digestible protein requirements and efficacy of high or low protein feeds 174

7.1.7 Diet formulation and fishmeal replacement................................................176

7.1.8 Implications of research for snapper industry.............................................177

7.2 CONCLUSIONS................................................................................................179

7.3 REFERENCES – Chapter 1 and Chapter 7........................................................181

7.4 APPENDICES ...................................................................................................193

XVII

LIST OF ABBREVIATIONS

Institutions:

ABARE Australian Bureau of Agricultural & Resource Economics

AOAC Association of Official Analytical Chemists

CRC Cooperative Research Centre

CSIRO Commonwealth Scientific & Industrial Research Organisation

DPI Department of Primary Industries

FALA Food & Agricultural Laboratories Australia

FAO Food & Agriculture Organisation

FRDC Fisheries Research & Development Corporation

HAPS Hunter Area Pathology Service

NRC National Research Council

PSFC Port Stephens Fisheries Centre

SARDI South Australian Research & Development Institute

SCL State Chemistry Laboratory

Other acronyms:

ADC apparent digestibility coefficient

ANOVA analysis of variance

ANCOVA analysis of covariance

$AUD Australian dollar

BV biological value

BW body weight

CHO carbohydrate

df degrees of freedom

DE digestible energy

DP digestible protein

exp exponent

FBW final body weight

FCR feed conversion ratio

GMBW geometric mean body weight

XVIII

HSI hepatosomatic index

IBW initial body weight

ICP-MS inductively coupled plasma – mass spectrometer

MJ mega joule

NFE nitrogen free extract

NPU net protein utilisation

PER protein efficiency ratio

PPV productive protein value

PRE protein retention efficiency

RAS recirculating aquaculture system

SD standard deviation

SEM standard error of mean

SGR specific growth rate

SKM saturation kinetics model

SNK Student Newmans Kuels test

TGC thermal growth coefficient

XIX

LIST OF FIGURES

Figure 1.1 Australian aquaculture production and value of production from 1988 to

2000. (Data adapted from O’Sullivan & Dobson 2003). ............................6

Figure 1.2 2003-04 Australian aquaculture production; including total crustacean and

mollusc production. (Data adapted from ABARE 2004; excludes

production of NT pearls due to confidentiality)..........................................7

Figure 1.3 2003-04 Australian Aquaculture production by value ($AUD); including

total crustacea and mollusc production (Data are adapted from ABARE

2004; excludes production of NT pearls due to confidentiality). ...............8

Figure 3.1 Effect of digestible protein intake on protein deposition in juvenile

snapper. Points represent mean ± SEM of 3 replicate cages.....................68

Figure 3.2 Effect of DP:DE ratio on protein deposition in juvenile snapper. Points

represent mean ± SEM of 3 replicate cages. .............................................72

Figure 4.1 Effect of digestible energy (DE) content on relative feed intake in juvenile

snapper. Points represent mean of 4 replicate cages. Outer curves

represent 95% confidence intervals. .........................................................99

Figure 4.2 Effect of relative digestible protein (DP) intake on weight gain of juvenile

snapper. Points represent mean of 4 replicate cages. Outer curves

represent 95% confidence intervals. .......................................................100

Figure 5.1 Effect of gelatinised wheat starch inclusion level on gross energy ADC.

Outer curves represent 95% confidence limits. Gross energy ADC =

104.97 – 0.109 x inclusion level (R2 = 0.86). .........................................124

Figure 5.2 Effect of intra-peritoneal injection of 1 g D-glucose kg BW-1, a sham

injection of saline or a handling stress on the 72 h plasma glucose

response of snapper. ................................................................................126

XXI

LIST OF TABLES Table 2.1 Measured composition of individual feed ingredients (g kg-1 or MJ kg-1 dry

matter). ......................................................................................................26

Table 2.2 Calculated ingredient and measured nutrient composition of diets used in

experiment 1 (g kg-1 or MJ kg-1 of dry matter). ........................................27

Table 2.3 Calculated ingredient and measured nutrient composition of diets used in

experiment 2 (g kg-1 or MJ kg-1 of dry matter). ........................................28

Table 2.4 Mean apparent digestibility coefficients (ADCs) for diets and ingredients

and specific growth rate (SGR) of snapper used in experiment 1.............33

Table 2.5 Mean apparent digestibility coefficients (ADCs) for diets and ingredients

and specific growth rate (SGR) of snapper used in experiment 2.............34

Table 2.6 Digestible protein and energy values of test ingredients fed to snapper....38

Table 3.1 Composition of test diets (g kg-1 or MJ kg-1 of dry matter). ......................56

Table 3.2 Performance of juvenile snapper in the growth experiment. .....................66

Table 3.3 Parameter estimates ± standard error derived from fitting relative protein

deposition in snapper as a function of DP content or DP intake...............69

Table 3.4 Parameter estimates ± standard error derived from fitting relative protein

deposition in snapper as a function of DP:DE ratio of diets. Data presented

as different curves for each data set and one curve for all data sets. ........70

Table 4.1 Measured chemical composition of major feed ingredients (g kg-1 or MJ

kg-1 dry matter basis).................................................................................89

Table 4.2 Ingredient composition and calculated digestible protein or energy content

of test diets fed to snapper (g kg-1 or MJ kg-1 dry matter).........................91

Table 4.3 Performance of snapper after 51 days on test diets....................................96

Table 4.4 Group performance of snapper reared on optimal or sub-optimal diets for

51 days. .....................................................................................................97

Table 5.1 Measured chemical composition of feed ingredients used in experiment 1

(g kg-1 or MJ kg-1 dry matter basis).........................................................115

Table 5.2 Calculated ingredient and measured nutrient composition of test diets used

in experiment 1 (g kg-1 or MJ kg-1 of dry matter). ..................................116

Table 5.3 Apparent organic matter and gross energy digestibility coefficients for

snapper fed diets containing increasing levels of gelatinised wheat starch.

.................................................................................................................123

XXII

Table 5.4 Hepatosomatic index (HSI), 3 h post-prandial plasma glucose

concentration and liver or tissue glycogen concentration of snapper fed

test diets with different levels of gelatinised wheat starch...................... 125

Table 6.1 Measured composition of individual feed ingredients in Exp.1 (g kg-1 or

MJ kg-1 dry matter). ................................................................................ 145

Table 6.2 Ingredient and nutrient composition of test diets used in Exp.1 (g kg-1 or

MJ kg-1 dry matter). ................................................................................ 146

Table 6.3 Ingredient, nutrient and energy composition of extruded diets used in

Exp.2 (g kg-1 or MJ kg-1 of dry matter)................................................... 148

Table 6.4 Performance of juvenile snapper fed diets with increasing levels of poultry

meal, meat meal or soybean meal after 50 days (Exp.1). ....................... 154

Table 6.5 Performance of snapper grown in 1m3 cages in an outdoor pond at PSFC

for 104 days (Exp 2)................................................................................ 156

Table 7.1 Formulated versus measured digestible protein (g kg-1) and digestible

energy (MJ kg-1) values of test diets used in Chapter 3. ......................... 172

Table 7.2 Apparent digestibility coefficients for snapper fed alternative Australian

based feed ingredients. Faeces collected by settlement methods............ 175

1

CHAPTER 1. GENERAL INTRODUCTION

General introduction 3

1.0 INTRODUCTION

1.1 Aquaculture: the world perspective

Aquaculture (the farming of aquatic plants and animals) has been the fastest

growing sector of global food production for more than three decades, growing at an

average compound rate of approximately 8.7% since the early 1970’s (Tacon 2004).

Over the same period, landings from wild capture fisheries have remained virtually

static (1.2% per year) and according to some sources may in fact already be declining

(Anon. 2003). Growth in the terrestrial meat production sector has only been

marginally better (2.9% per year) (Tacon 2003; 2004). Over 50% of capture fisheries

are now almost fully exploited and 70% are listed as in need of urgent management

(Anon. 2003; Allan 2004). For this reason capture fisheries are unlikely to make major

contributions to fisheries landings in the future. In contrast, total world aquaculture

production reached approximately 51.4 million metric tonnes (mmt) in 2002, or more

than half the amount produced by global capture fisheries (FAO 2004; Tacon 2004).

The culture of finfish species represented more than 50% of total aquaculture

production (25.7 mmt), valued at approximately $US32 billion, the majority of the

remainder coming from molluscs, aquatic plants and crustaceans, which accounted for

11.8, 11.6 and 2.1 mmt respectively. By region, aquaculture production was highest in

the developing Asian countries (especially China), which are now responsible for over

90% of total aquaculture production valued at $US49.3 billion (Tacon 2003; 2004).

Europe, Latin America and the Caribbean, North America, Africa and Oceania were

each responsible for 4.0, 2.3, 1.3, 0.9 and 0.3% of total aquaculture production

respectively (Tacon 2004). Although the larger proportion of aquaculture production

was accounted for by developing countries (especially China), the majority of fin fish

produced in these regions was of lower value, typically being omnivorous / herbivorous

or filter feeding species (i.e. cyprinids, tilapia, catfish) for domestic consumption.

Aquaculture production of finfish in developed countries is generally based on higher

value species, typically marine or freshwater carnivores (salmonids, sparids). For this

reason, developed countries were responsible for nearly 18% of total aquaculture

production by value in 2002 (New 1997; Tacon 2004).

Growth in world aquaculture is being driven primarily by population

growth, which is predicted to reach about 8 billion by 2030 (Tacon 2003). This increase

will place enormous demands on not only the remaining capture fisheries, but also on


aquaculture. For example, the world average per capita annual consumption of fish has

now increased from about 5 kg in 1961 to 24.8 kg in 2001 (Brugere & Ridler 2004),

although the per capita consumption of fish often varies widely, depending on

geographic region, wealth and access to product (New 1997; Delgado, Wada,

Rosengrant, Meijer & Ahmed 2003). Fish remains one of the most important sources of

protein in the developing world, where fish protein accounts for approximately 25% of

total protein intake. In contrast, consumers in Europe and North America, who have

access to a greater variety of protein sources through terrestrial agriculture, consume as

little as 10% of their protein as fish (Allan 2004). Given the predictions in population

growth and the increasing trends in the average per capita intake of fish over time, it is

critical that aquaculture production continues to grow in order to meet the future global

demands for seafood (Brugere & Ridler 2004).

1.2 Increased demand for compound aquafeeds: fishmeal and fish oil

The rapid expansion and intensification in aquaculture production of finfish

has resulted in increased demand for high quality aquaculture feeds. Approximately

17.8 mmt of compound aquafeeds were produced in 2002, with the majority allocated

to production of feeding carps (47%) (Tacon 2003; 2004). Compound aquafeeds are

still based almost exclusively on fishmeal and fish oil, especially for carnivorous finfish

and crustaceans (Tacon & Forster 2001; Coutteau, Ceulemans, Van Halteren & Robles

2002). Currently, these commodities are produced by rendering approximately 30-36

mmt year-1 of “bait” or “industrial” quality fish such as anchovie, sardine, anchovetta,

herring and capelin etc. (Coutteau et al. 2002; Allan 2004) sourced under strict quotas

from the trawl industries of Peru, Chile, Iceland, Denmark and Norway (Pike & Barlow

2003), into 6-7 and 1-1.5 mmt of fishmeal and fish oil, respectively. Production of

compounded aquafeeds consumed about 2.4 mmt of fishmeal and 0.6 mmt of fish oil in

2000, or the equivalent of 35% and 41% respectively of total world supplies (Tacon

2003), the rest being consumed by the poultry and swine industries or used as fertiliser.

However, like the majority of other capture fisheries, landings of “industrial” fish have

remained static for decades. This is significant for the growth of aquaculture, as it will

mean that competition for these resources will increase, ultimately making them

increasingly expensive. The sporadic production of fishmeal and fish oil due to

fluctuations in total landings from year to year also places a high degree of uncertainty

over the availability of these resources, exemplified by the dramatic drop in catch and


subsequent escalation in price during El-Nino events such as 1998 (Coutteau et al.

2002). During this particular event the price of fishmeal exceeded $US700 per metric

tonne before falling to approximately $US350 by the end of 1999. Since then, world

fishmeal prices have been steadily escalating and the average price of high quality

fishmeal (excluding freight) is currently $US620 per metric tonne. Fish oil is also

becoming increasingly expensive and now commands $US600 metric tonne (excluding

freight) (Hammersmith Marketing Report March 2005; http://www.aquafeed.com).

The use of fishmeal and fish oil in aquafeeds has become increasingly

controversial over the past decade, with many commentators expressing concerns about

the environmental costs of feeding fish to fish (Naylor, Goldberg, Primavera, Kautsky

et al. 2000; see Tidwell & Allan 2001 or Pike & Barlow 2003 for alternative view).

The potential collapse of fishmeal production has also raised longer-term ethical

concerns about the redirection of low value fish currently feeding the developing world

to the aquaculture production of higher value species in developed countries (Delgado

et al. 2003; Tacon 2003; Anon. 2003). In general, these concerns appear to be directed

more at the reliance of aquaculture sectors producing omnivorous / carnivorous species

effectively resulting in a net loss of “fish biomass” from the environment (Naylor et al.

2000; Tacon & Forster 2001; Tacon 2003). These concerns may be valid in certain

circumstances, however the aquaculture sector is moving rapidly to reduce reliance on

these commodities as it continues to grow. This is being achieved mostly through

research to determine the nutritional requirements and best feeding strategies for

different aquaculture species (i.e. so that aquafeeds provide but do not oversupply

dietary nutrients) and ongoing research into the viability of alternatives to fishmeal and

fish oil (Tidwell & Allan 2001; Anon. 2003; Allan 2004). This type of research is at its

inception for many species, while for others it is well established (e.g. aquaculture

production of salmonids has been developing for nearly 30 years)♣. Accordingly, the

reliance of the aquaculture sector on fishmeal and trash fish (and fish oil) is predicted to

decline over the coming decades (Tacon 2004), in much the same way it has in the

poultry and swine industries (Pike & Barlow 2003; Allan 2004). In addition, finite ♣ The Australian silver perch Bidyanus bidyanus serves as useful example of how a research based approach to understanding the

dietary nutrient requirements of this species and its capacity to utilise alternative feed ingredients has led to production based feeds

containing no fishmeal (Allan, Rowland, Parkinson, Stone & Jantrarotai 1999; Allan, Parkinson, Booth, Stone, Rowland, Frances

& Warner-Smith 2000a; Allan, Stone, Booth & Rowland 2000b; Allan, Johnson, Booth & Stone 2001; Booth & Allan 2003; Allan

& Booth 2004).


supplies of fishmeal coupled with the growing pressure from China (the biggest user of

rendered fishmeal), will encourage the use of alternative feed ingredients.

Consequently, countries that have well developed agricultural and or rendering based

industries that produce significant volumes of high quality feed grade proteins and oils

(animal or plant based) will be well placed to exploit shortfalls in the production of

fishmeal and fish oil resources.

1.3 Aquaculture: the Australian perspective

By world standards, aquaculture production in Australia remains in its

infancy, but it continues to follow global trends (Figure 1.1). In real terms, aquaculture

production has increased from $AUD494 million in 1994-95 to $AUD732 million in

2003-04 and is growing at an annual average rate of 4%. Australian aquaculture

production now accounts for 34% of the total gross value of fisheries production

(ABARE 2004).

0

5

10

15

20

25

30

35

40

45

50

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

Production year

Production Tonnes (000s)

0

100

200

300

400

500

600

700

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Value $AUD million

Tonnes (000 s)Value (AU$ million)

Figure 1.1 Australian aquaculture production and value of production from 1988 to

2000. (Data adapted from O’Sullivan & Dobson 2003). At present, the production of Atlantic salmon Salmo salar, molluscs (edible) and

Southern blue-fin tuna Thunnus maccoyii dominate the Australian aquaculture industry

(Figure 1.2). Aquaculture production of finfish is dominated by Atlantic salmon with


between 13.5 and 14.5 kilo tonnes (kt) produced annually. Southern blue-fin tuna (9.3

kt ), trout (1.9 kt) and barramundi Lates calcarifer (1.6 kt) account for the bulk of the

remainder. By value, southern blue fin tuna and mollusc production account for

approximately 35.1% ($AUD242.0 million) and 34.2% ($AUD235.6 million; 67%

attributable to pearl oysters) of the total value of Australian aquaculture production,

respectively. The high value of both these sectors is related to the international demand

for these products; consequently, the majority of farmed tuna and pearl oysters are

produced for export. Atlantic salmon (16.8% and $AUD115.7 million), crustaceans

(mostly prawns, yabbies and redclaw; 8.6% and $AUD59.5 million), barramundi (1.9%

and $AUD13.4 million) and trout (1.9% and $AUD12.9 million) account for the

majority of the remainder (ABARE 2004).

Salmon Trout Tuna Silver Perch Barrumundi Other finfish Crustaceans Molluscs

Salmon 34.9%

Trout 4.4%

Southern blue-fin tuna 21.8%

Molluscs 24.6%

Crustaceans 8.9%

Other finfish 1.1%

Barramundi 3.7%

Silver perch 0.7%

Figure 1.2 2003-04 Australian aquaculture production; including total crustacean and mollusc production. (Data adapted from ABARE 2004; excludes production of Northern Territory pearls due to confidentiality).

Aquaculture of the freshwater native, silver perch Bidyanus bidyanus is a small but

stable industry producing about 300 tonnes per year worth $AUD2.7 million. Other

finfish (Figures 1.2 & 1.3) include eels (Anguilla spp.), other native fish and small

quantities of marine finfish such as snapper Pagrus auratus, mulloway Argyrosomus


japonicus and yellowtail kingfish Seriola lalandii valued collectively at approximately

$AUD7.6 million in 2003-04 (Figure 1.3).

Australian consumers have also increased their annual per capita intake of

seafood, up from 4.9 kg in the 1930’s to approximately 15 kg in 1999 (FRDC 2002).

This demand has created a seafood deficit, which is now met by importing 0.14 mmt

($AUD544.8 million) of edible seafood products from other countries due to the static

or declining catches of our own commercial fisheries (Allan 1999; ABARE 2004).

Paradoxically, Australia exports almost 80% of its edible aquaculture and fisheries

products including rock lobster, tuna, abalone and prawns (ABARE 2004).

Salmon Trout Tuna Silver Perch Barrumundi Other finfish Crustaceans Molluscs

Molluscs 34.2%

Salmon 16.8%

Trout 1.9%

Southern blue-fin tuna 35.1%Crustaceans 8.6%

Silver perch 0.4%Barramundi 1.9%

Other finfish 1.1%

Figure 1.3 2003-04 Australian Aquaculture production by value ($AUD); including total crustacea and mollusc production (Data are adapted from ABARE 2004; excludes production of Northern Territory pearls due to confidentiality).

High value products tend to be exported while the majority of imported products are

lower value frozen or canned products (ABARE 2004).

1.4 Marine finfish aquaculture in Australia

As indicated above, large-scale aquaculture of marine finfish in Australia is

currently limited to production of Southern blue-fin tuna (South Australia), Atlantic


salmon (Tasmania) and barramundi (predominantly Queensland, New South Wales and

Northern Territory; although some intensive indoor recirculating aquaculture systems

now operate in South Australia and Victoria). Besides these species, the aquaculture

potential of as many as 20 other marine finfish have or are currently being explored in

Australia (Fielder 2003). Many of these are being evaluated in an attempt to offer

diversity within the tuna and salmon industries in Australia, or provide species for

similar industries in new areas. Some of these species support significant aquaculture

industries in other countries. Examples include the sea-cage grow-out of Yellowtail

(Japanese amberjack) Seriola quinqueradiata and Red sea bream Pagrus major in

Japan (Watanabe & Vassallo-Agius 2003) and the farming of Gilthead seabream

Sparus aurata in the Mediterranean (Basurco & Lovatelli 2005). These industries have

been successful because they have developed a series of integrated technologies that

encompass brood-stock management, larval rearing (hatchery), nursery and grow-out

phases through either industry or government based research (Foscarini 1998;

Watanabe & Vassallo-Agius 2003). In most cases, the basic nutritional requirements of

these species is also well understood (Foscarini 1998).

In New South Wales (NSW), commercial farming of marine fish is

developing and is principally based on the seacage grow-out of snapper and mulloway.

Intensive freshwater production of barramundi (euryhaline species) is also developing,

but is conducted in recirculating aquaculture systems (Fielder, Booth & Allan 2003).

The aquaculture of other marine finfish in NSW waters will most likely be limited to

other temperate water species such as yellowtail kingfish, bream (Acanthopagrus

butcheri or A. australis) or sand whiting Sillago ciliata, although interest in culturing

the common dolphinfish (mahimahi) Coryphaena hippurus and cobia (black kingfish)

Rachycentron canadum has been expressed. The prevailing sea temperatures are

considered unsuitable for the culture of either tropical or cold-water species (Fielder

2003; Fielder et al. 2003).

1.5 Potential of Australian snapper Pagrus auratus

Interest in the culture of snapper in Australia is driven by several factors.

Firstly, the species is highly valued as both a recreational sport fish and for its eating

qualities. For this reason snapper generally command a high retail price of between

$AUD12-15.00 kg-1. Secondly, the commercial catch of snapper from Australian

waters is declining and has fallen to approximately 1.7 kt per year (ABARE, 2004).


The domestic appetite for snapper remains high, and approximately 1.2 kt of snapper

are imported from New Zealand each year to meet this demand (Fielder 2003). Thirdly,

the technology for the aquaculture of red sea bream is well developed in Japan, where

between 60 to 80 kt have been produced on an annual basis since 1992 (Koshio 2002;

Watanabe & Vassallo-Agius 2003). This is particularly relevant because snapper and

the red sea bream are closely related species (Paulin 1990; Tabata & Taniguchi 2000),

thus the potential for a similar type of sea cage industry in Australia based on

translocated Japanese technology appears to be very promising (Bell, Quartararo &

Henry 1991; Quartararo 1996; Fielder 2003; Partridge & Jenkins 2003). The potential

for snapper farming has also been highlighted by the rapid expansion in the sea cage

production of another sparid over the last decade, the gilthead seabream, with more

than 80 kt of this fish produced in Mediterranean waters each year (Basurco &

Lovatelli 2005). However, the environmental, economic and policy structures that

make the farming of the red and gilthead sea breams economical in Japan and the

Mediterranean are not present in Australia, meaning that until these factors are

identified or overcome, successful aquaculture of snapper may be hindered or fail to

proceed at all.

1.6 Current status of snapper culture: Japan

The majority of aquaculture research on snapper (i.e. red sea bream) has been

conducted in Japan, where this species has been reared experimentally since the early

1900’s (Foscarini 1998) and cultured commercially since the mid 1960’s (Watanabe &

Vassallo-Agius 2003). The Japanese red sea bream industry grew out of the increasing

wealth of the Japanese consumer and their desire to consume high rather than low value

fish. Consequently, the red sea bream industry was initially established by feeding

lower value “trash” fish diverted from other domestic uses (Foscarini 1998). However,

the expansion of this industry and falls in the catch of “trash” fish such as sardines, jack

mackerel and sand lance necessitated the move towards semi-moist and eventually dry

based feeds to improve the economics of farming and meet increasingly stringent

environmental regulations (Watanabe & Vassallo-Agius 2003). Today, the Japanese

production of red sea bream demands approximately 180 kt of aquafeed per year

(Koshio 2002).

Broodstock management, larval rearing and grow-out technologies are well

developed for red sea bream (Foscarini 1998; Koshio 2002; Fielder 2003; Watanabe &


Vassallo-Agius 2003). Nutritional studies commenced in the 1970’s, and results were

generally based on purified protein sources (Yone 1976). Studies prior to 1990 on the

nutritional requirements of red sea bream were mostly based on moist or semi-moist

pellets (>30% moisture) but the majority of work since then has been based on dry

feeds (Koshio 2002). Much of the diet research in Japan has been sponsored by private

feed companies and as such, feed formulations and production results are held in

confidence. Publication of specific nutritional research on this species in the scientific

literature is also limited and often unavailable, but general dietary requirements for red

sea bream are estimated at between 40-55% crude protein, 10-15% lipid, 10-15%

carbohydrate (CHO) and 15-21% ash (Foscarini 1988; Koshio 2002). These values

approximate those for other cultured sparids such as the gilthead seabream (Kaushik

1997), but, the scope for improving the composition and formulation of feeds for these

species is probably quite extensive. Apparent digestibility coefficients for a diverse

range of ingredients have also been published for the red seabream (Yamamoto,

Akimoto, Kishi, Unuma & Akiyama 1998) and gilthead sea bream (Nengas, Alexis,

Davies & Petichakis 1995; Lupatsch, Kissil, Sklan & Pfeffer 1997).

1.7 Current status of snapper culture: Australia

The snapper industry in Australia remains in its infancy, limited to a certain

extent by the lack of suitable protected coastal sites for sea cage culture (Doroudi,

Allan & Fielder 2003; Partridge & Jenkins 2003) and the dependence on commercial

diets formulated for other species such as barramundi and Atlantic salmon (Booth,

Allan & Anderson 2005). Research into the viability of snapper farming in Australia

has been conducted since the early 1990’s, predominantly in NSW, but also in South

Australia (SA) and Western Australia (WA). Small-scale commercial ventures have

been established in NSW at Providence Bay (Port Stephens, NSW, Australia) and

Silver Beach (Botany Bay, NSW, Australia). In South Australia, snapper research has

been conducted by the South Australian Research and Development Institute (SARDI)

and sea cage farming has been investigated in the protected waters of the Spencer Gulf

at Fitzgerald Bay, Cowell and Port Lincoln. At present, marine finfish farmers in SA

are focusing on production of mulloway and yellowtail kingfish due to the poor

economic returns associated with the production of snapper (Hutchinson 2003).

Production of snapper in WA is currently limited to small-scale research facilities at the

Aquaculture Development Unit (ADU) Challenger TAFE, Freemantle (Partridge &


Jenkins 2003). Due to the particular geography of the WA coastline and potential

conflicts with other stakeholders, development of a sea cage industry in WA is

unlikely. However, there is potential in WA, as in other mainland states of Australia

(Doroudi, Allan & Fielder 2003; Hutchinson 2003), to exploit inland saline

groundwater evaporation basins for marine finfish production (Partridge & Jenkins

2003).

A wide variety of research has been conducted with Australian snapper in

Australia. The NSW Department of Primary Industries (DPI; Fisheries) commenced

research into the viability of snapper farming in the early 1990’s with a project funded

by the Fisheries Research and Development Corporation (FRDC) entitled “Potential of

snapper Pagrus auratus for aquaculture”. These pilot scale studies indicated that

snapper could be successfully grown in sea cages (Bell et al. 1991; Quartararo 1996).

Several preliminary nutritional studies were also undertaken at this time to investigate

the potential of replacing fishmeal with a small range of alternative Australian feed

ingredients such as poultry meal, lupins and soybean meal (Quartararo, Bell & Allan

1998a; Quartararo, Allan & Bell 1998b). Snapper research in WA has focused on

improving hatchery technologies and feeding strategies, the evaluation of agricultural

ingredients of particular relevance to WA (e.g. lupins and canola) and bio-energetic

modeling of protein and energy requirements (Glencross, Kolkovski, Jones, Felsing &

Saxby 2003c; Glencross & Lupatsch, unpublished data). Other researchers have

focused on improving maturation and spawning cycles of broodstock snapper

(Battaglene & Talbot 1992; Battaglene 1995; Fielder, Allan & Battaglene 1999) and

understanding the effects of stress on reproduction (Cleary 1997). Fielder (2003) has

recently presented an extensive research thesis detailing advances in intensive larval

rearing technology and changes in the physiology of snapper reared in potassium

deficient ground-water. In addition, Glencross, Curnow, Hawkins, Kissil & Peterson

(2003a) and Glencross, Hawkins & Curnow (2004) have published data on digestibility

coefficients for snapper fed Australian lupins and canola meals. These authors have

also evaluated the potential of refined soybean and canola oils as replacements for fish

oil in diets for snapper (Glencross, Hawkins and Curnow 2003b). Since the publication

of these results, the combined production of snapper from the two marine based farms

in NSW has climbed from about 0.4 t in 1998-99 to approximately 40 t in 2002-03 with

the majority of fish presented to the market ranging from 450 to 550 g (Fielder et al.

2003).


1.8 Constraints to growth of Australian snapper industry

Despite the potential of Australian snapper and the contributions made by the

aforementioned research, several major problems continue to hinder the expansion and

viability of snapper farming in NSW. These include the reliable supply of high quality,

cheap fingerlings, the lack of high performance diets and feeding systems for both

hatchery and grow-out, the unnatural dark skin colour of farmed snapper (Hutchinson

2003: Booth, Warner-Smith, Allan & Glencross 2004) and ongoing problems with

infestation of dinoflagellate parasites such as Amyloodinium ocellatum (Fielder et al.

2003). To address these issues, NSW DPI Fisheries has joined an Australian

Commonwealth joint venture research project funded by the Fisheries Research and

Development Corporation (FRDC), research providers, universities and key industry

associations and companies. This collective is known as the Cooperative Research

Centre (CRC) for the Sustainable Aquaculture of Finfish and commenced in 2001. The

CRC’s broad purpose is “to meet the major needs of the Australian finfish and

aquaculture industry for new and improved technologies, to provide reliable scientific

information for environmental risk managers and to enhance the skills of people

working in and for aquaculture” (Montague 2003). Through this CRC, NSW DPI

Fisheries is conducting a research project entitled “Increasing the profitability of

snapper farming by improving hatchery practices and diets; Project 2.3; FRDC Project

Number 2001/208” (Aquafin CRC 2003). Ostensibly, this project aims to address the

issues raised above and is conducted at the NSW DPI Fisheries, Port Stephens Fisheries

Centre, NSW Australia.

The work presented in this thesis is drawn from the nutritional component of the

research outlined in CRC Project 2.3. The data presented is based on a series of studies

designed to increase our knowledge of the nutritional requirements of Australian

snapper and provide additional information on Australian feed ingredients for use in

diets for this species.

1.9 Need for research

For the snapper industry to reach its potential in NSW (Australia), nutritionally

adequate, locally produced and cost effective feeds must be developed. To date there

are no commercial feeds manufactured exclusively for snapper and farmers rely on

feeds formulated specifically for Atlantic salmon and barramundi. The cost of


purchasing and delivering feeds is still the single highest operating cost for most types

of fish culture, often accounting for between 30 to 60% of on-farm operating costs

(Allan & Rowland 1992; Koven 2002). In Australia, locally produced grow-out feeds

for marine or freshwater carnivorous species generally exceed $AUD1300 tonne-1

(Ridley Aqua-Feed Pty Ltd., Narangba, Qld, Australia; standard price guide Feburary

2004). The cost of grow-out feeds has been as high as $AUD1800 to $AUD2000 tonne-

1 (Skretting Pty Ltd; Tasmania, Australia; standard price guide 2004).

Aquafeed costs in Australia are driven primarily by the international availability

and price of fishmeal and fish-oil and the prevailing currency exchange rates. Australia

imported $AUD19.3 million worth of fishmeal for use in aquaculture and terrestrial

stock-feeds in 2003-04 (ABARE, 2004). The price of feeds for Australian snapper

farmers is also affected by the small scale of their operations, with feed companies

charging higher premiums for smaller orders. The small scale of these farms also

makes the importation of red sea bream diets from Asia prohibitive (Status of Fisheries

Resources 2001).

For the snapper industry to reach its potential in NSW (Australia), nutritionally

balanced diets that meet but do not exceed the nutritional requirements of this species

must be developed. Earlier studies with snapper also recognised that, unless low cost,

locally available alternatives to fishmeal could be identified, the development of a

large-scale Australian industry based on this species was unlikely (Quartararo et al.

1998a). This need is still paramount, primarily because large volumes of fishmeal will

not be produced in Australia and the global pressures on fishmeal will continue to grow

(Booth et al. 2005). Consequently, the cost of incorporating imported fishmeal into

locally produced aqua-feeds links Australian feed manufacturers to the global supply of

fishmeal and the volatility of foreign exchange rates (Akiyama & Hunter 2001).

Independence from these economic constraints will only be possible when suitable feed

alternatives are identified.

Reducing the costs of snapper diets will involve either partial or total

replacement of fishmeal with alternative, locally available protein sources. Further

reductions in costs may be afforded by the partial substitution of fish oil with other

energy sources such as vegetable oils (Glencross et al. 2003b) or carbohydrates (Stone

2003). Research into reducing the dependence of aquaculture diet formulations on

fishmeal is well advanced internationally, and many of the more promising ingredients


identified in these studies are abundant and readily available in Australia (Allan et al.

2000a; Stone 2002).

Suitable ingredients for partial or complete replacement of fishmeal fall into

two basic categories; either 1) plant or 2) animal based protein and energy sources.

Each of these categories can be further divided into by-product meals, protein

concentrates, isolates or other highly processed derivatives. Invariably, the more

processing that is involved the more expensive the ingredient will become. Ingredients

that are more expensive to produce will also generally elevate the cost of manufactured

feeds rather than decrease them, an outcome that is often amplified if the size of an

industry is small and the associated economies of scale are absent. Feed formulators /

manufacturers thus require access to readily available, reliable and competitively priced

ingredient streams to incorporate in aquaculture feeds. Ideally, these resources would

be of local origin.

1.10 Digestibility and utilisation of feeds and feed ingredients

The major issues associated with feed development include an understanding of

the nutritional requirements of the species coupled with access to a diverse range of

ingredients for which the nutritional limitations with respect to the ingredient and the

species are known (Kaushik 1997).

The first task in evaluating the potential of any ingredient for inclusion in

finfish diets should be the determination of its apparent digestibility (Cho, Slinger &

Bayley 1982; Allan et al. 1999; Bureau, Kaushik & Cho 2002). Preferably, the

digestibility of an ingredient should be investigated at several practical inclusion levels

to ensure that apparent digestibility coefficients are additive (Allan et al. 1999).

Collection of faecal material from fish is a difficult process, and collection methods

must ensure results are accurate, reproducible and amenable to the fish (Austreng 1978;

Cho et al. 1982; Allan et al. 1999). Apparent digestibility coefficients are also

necessary to allow experimental and commercial feeds to be formulated on a

“digestible” rather than a gross nutrient basis. This ensures feeds account for the

undigested fraction of each ingredient employed in the formulation. Use of apparent

digestibility coefficients is necessary to establish or confirm the “digestible” protein

and energy requirements for growth and maintenance of snapper.

At present, both economic and ethical considerations demand the most

efficient utilisation of feeds and feed ingredients for all farmed species. Therefore, the


most efficient conversion of these nutrient sources into high quality, edible product is

the ultimate goal of both researchers and farmers alike (Pfeffer 1982; Bikker 1994).

One of the major problems with evaluating the utilisation of ingredients by fish,

as is the case in evaluation of digestibility, is that they are generally unacceptable to

fish when fed in isolation. Furthermore, the nutritional limitations of some ingredients,

such as an inferior amino acid composition, preclude their use unless they are

combined with other ingredients that complement the particular deficiency. The

presence of anti-nutrients in some ingredients can also make their inclusion

problematic, given that they may affect either palatability (reduced voluntary intake) or

utilisation (Tacon 1995; Booth, Allan, Frances & Parkinson 2001). This creates

somewhat of a dilemma, because, unless direct and expensive techniques are used, such

as enriched stable isotopes (Preston, Smith, Kellaway & Bunn 1999; Smith, Barclay &

Tabrett 1999), it is extremely difficult to evaluate the utilisation of an ingredient within

a diet independently of the other ingredients combined with it. This is further

complicated by the potential interactions that may exist between ingredients, either

advantageous or deleterious. In addition, the complex relationship between an animal’s

nutritional requirements under different physiological conditions (e.g. maintenance,

growth, reproduction), and the interplay between the levels and source of dietary

protein, energy, vitamins and minerals have major affects on utilisation (Cho et al.

1982; Hepher 1988, NRC 1993; Bikker 1994).

Other factors affect the utilisation of ingredients (nutrients) including feeding

level and frequency, fish size or age, fish species and nutritional strategy (i.e. obligate

or facultative herbivore, omnivore or carnivore) and the environmental conditions

experienced by the animal (Cho et al. 1982; Hepher 1988). Understanding the

utilisation of ingredients is also complicated by the fact that fish are capable of

catabolising proteins, fats and carbohydrates for energy (Cho et al. 1982; Hepher 1988;

Lupatsch, Kissil, Sklan & Pfeffer 2001). The fact that some fish are capable of

efficiently utilising the energy from carbohydrates as well as lipid sources to spare

protein has nutritional as well as economic implications (Wilson 1994; Stone 2003).

As a first step, measurement of digestibility is critical and extremely useful in

identifying the potential of an ingredient. However, digestibility is not a measure of

utilisation. To evaluate utilisation, the accumulation or otherwise of feed nutrients

(specifically protein and energy) into body tissues must be ascertained. In general,

weight gain, specific growth rate (SGR) and feed conversion ratio (FCR) or its


reciprocal, feed conversion efficiency, are the most widely used criteria to evaluate the

utilisation of diets (Hepher 1988). The calculation of thermal growth coefficients

(TGC) has also now become a well-accepted method of comparing growth and

assessing performance of diets (Bureau et al. 2002). Protein efficiency ratio (PER) is

commonly used to evaluate utilisation of dietary protein. The efficiency of dietary

energy may be evaluated in much the same way. These measures of utilisation are

relatively simple to obtain but make no allowances for changes in carcass composition.

PER also assumes that all the protein in the diet is utilised for tissue synthesis and

ignores requirements for maintenance (Hepher 1988). A more rigorous measure of

protein utilisation is protein retention efficiency (PRE), also known as productive

protein value (PPV), which is usually determined by comparative slaughter techniques

and the accurate measurement of feed intake. Similar, but more refined measures

include net protein utilisation (NPU) and biological value (BV) (Hepher, 1988; Wilson

1989). These relationships are easily extended to determination of energy retention.

1.11 Scope and aims of study

The overall objective of the research described in this thesis was to increase

knowledge of the nutritional requirements of Australian snapper and provide additional

information on the potential of Australian feed ingredients to reduce or replace

fishmeal in diets for this species.

The specific aims of this study were to determine:

the apparent digestibility coefficients (ADC’s) of a range of potential feed

ingredients at different dietary inclusion levels,

the optimum digestible protein requirement of snapper at varying digestible

energy contents,

the effects of digestible protein content and digestible energy content and source

on weight gain and performance of snapper fed diets formulated to optimum

protein and energy ratios,

the effects of inclusion level on the apparent digestibility of gelatinised starch

and ability of snapper to regulate or tolerate CHO (glucose),

the effect of increasing levels of rendered animal meals or soybean meals on

growth, performance and body composition


the performance of snapper fed diets containing reduced contents of fishmeal

This thesis is presented as a series of 5 manuscripts that have been formatted

and submitted for publication in the international journal Aquaculture Research. As

such, the specific references for each manuscript are presented following the discussion

at the rear of each chapter. References for the general introduction and discussion are

presented at the rear of the thesis as are the relevant Animal Research Authorities. The

results of the research conducted to address the specific aims of this study are presented

in Chapter’s 2 through 6 of the thesis.

This thesis presents a cohesive body of work investigating the nutritional

requirements of Australian snapper Pagrus auratus that applied a research approach

based on the determination of apparent digestibility coefficients for individual feed

ingredients (Chapter 2). Determination of these coefficients made it possible to

formulate experimental diets on a digestible protein and energy basis. These diets were

then used to investigate the relationships between digestible protein (DP) and digestible

energy (DE) and determine the optimal DP:DE requirements for juvenile fish (Chapter

3). Establishment of these requirements permitted elucidation of the effects of varying

not only the absolute content of DP and DE, but also the composition (source) of DE in

diets while maintaining an optimal ratio of DP:DE (Chapter 4). Increasing pressure on

the use of fishmeal and fish oil resources has encouraged the use of carbohydrates in

the diets of marine fin fish. Accordingly, the apparent digestibility of gelatinised wheat

starch was determined for snapper at various inclusion levels. A glucose tolerance trial

was done to investigate aspects of carbohydrate utilisation and tolerance (Chapter 5).

Finally, a series of experimental diets were formulated to test the effect of different

feed ingredient inclusion levels on weight gain and performance of snapper and to

elucidate effects on carcass composition. Results from this investigation were

ultimately used to formulate three commercially manufactured feeds for snapper that

replaced different amounts of fishmeal with a blend of alternative feed ingredients.

These feeds were tested in a semi-commercial production experiment (Chapter 6).

Chapter 7 contains a general discussion encompassing the outcomes of the

preceding 6 chapters as well as concluding remarks.

19

CHAPTER 2. APPARENT DIGESTIBILITY OF PROTEIN AND ENERGY SOURCES



apparent digestibility of protein and energy sources. Aquaculture Research 36, 378-

390.

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This article is not available online. Please consult the hardcopy thesis available from the QUT Library

49

CHAPTER 3. EFFECTS OF DIGESTIBLE ENERGY CONTENT ON UTILISATION OF DIGESTIBLE PROTEIN


requirements of Australian snapper Pagrus auratus (Bloch & Schneider, 1801): effects

of digestible energy content on utilisation of digestible protein. Aquaculture Research.

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81

CHAPTER 4. WEIGHT GAIN AND PERFORMANCE ON DIETS PROVIDING AN OPTIMAL RATIO OF DIGESTIBLE PROTEIN:DIGESTIBLE ENERGY, BUT DIFFERENT DIGESTIBLE PROTEIN AND ENERGY CONTENTS.


requirements of Australian snapper Pagrus auratus (Bloch & Schneider, 1801): weight

gain and performance on diets providing an optimal ratio of digestible

protein:digestible energy, but different digestible protein and energy contents.


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109

CHAPTER 5. DIGESTIBILITY OF GELATINISED WHEAT STARCH AND CLEARANCE OF AN INTRA-PERITONEAL INJECTION OF D-GLUCOSE

Booth, M.A., Anderson, A.J. & Allan, G.L. (in press) Investigation of the nutritional


digestibility of gelatinised wheat starch and clearance of an intra-peritoneal injection of

D-glucose. Aquaculture Research.

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139

CHAPTER 6. INFLUENCE OF POULTRY OFFAL MEAL, MEAT OR SOYBEAN MEAL INCLUSION LEVEL ON WEIGHT GAIN AND PROTEIN RETENTION



influence of poultry offal, meat or soybean meal inclusion level on weight gain and

protein retention. Aquaculture Research.

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167

CHAPTER 7. GENERAL DISCUSSION AND CONCLUSIONS

General discussion and conclusions 169

7.1 GENERAL DISCUSSION

This thesis describes research that has increased our knowledge of the

nutritional requirements of Australian snapper Pagrus auratus and provided

information on the potential of Australian feed ingredients to reduce the level of

fishmeal in diets for this species. To meet the general and specific aims of this study, a

research strategy based on determination of apparent digestibility coefficients (ADC’s),

establishment of DP:DE requirements, efficacy of high or low protein diets and an

understanding of ingredient utilisation was used.

7.1.1 Importance of digestibility in nutrition research

Before feed ingredients can be catabolised for fuels (energy) or utilised in

anabolic processes by fish (i.e. animals), they must be digested and absorbed from the

digestive system. Some ingredients resist digestion and pass through the digesitive tract

to be voided as faeces (Bureau, Kaushik & Cho 2002). Egested faecal matter contains

energy (i.e. faecal energy) and nutrients (e.g. crude protein, amino acids, lipids etc),

which can be deducted from the gross energy or nutrient intake attributable to feeds or

feed components to determine their digestible energy or nutrient value (Bureau et al.

2002). As faecal losses of energy or nutrients are the major pathway for loss of ingested

energy or nutrients from diets (or ingredients) in fish, it is imperative to determine the

digestible energy or nutrient value of feed components before formulating experimental

or commercial diets. Knowledge of the digestibility (availability) of ingredients is

critical and enables diets to be formulated that optimise the balance between nutrient

requirements and the cost of feeds (Lupatsch, Kissil, Sklan & Pfeffer 1997).

The use of digestibility coefficients in feed formulation is dependant largely

upon the premise that digestibility coefficients for protein, lipid, carbohydrate and gross

energy of individual ingredients are additive (Hardy 1997). Thus, the ADC’s for energy

or a specific nutrient in a complete diet should be entirely predictable according to the

ADC’s for energy or specific nutrients attributable to the individual feed ingredients

(Hardy 1997; Lupatsch et al. 1997). This concept also applies to amino acids (Lupatsch

et al. 1997; Allan, Parkinson, Booth, Stone, Rowland, Frances & Warner-Smith

2000a), fatty acids (Sklan, Prag & Lupatsch 2004) and minerals (Sugiura, Dong,

Rathbone & Hardy 1998). The additive nature of digestibility coefficients has generally

been demonstrated in many fish species with regard to protein and lipid rich ingredients


(Bureau et al. 2002). However, the additivity of digestibility coefficients for

carbohydrate (CHO) rich ingredients is particularly unreliable and is affected by type of

CHO (Lupatsch et al. 1997), cooking method (Wilson 1994; Stone 2003) and inclusion

level (Bergot & Breque 1983; Hemre, Lie, Lied & Lambertsen 1989; Stone, Allan &

Anderson 2003; Booth, Allan & Anderson 2005). For this reason, it is particularly

important that digestibility coefficients for CHO rich ingredients be determined at a

range of inclusion levels.

7.1.2 Digestibility coefficients for snapper

This thesis has determined apparent digestibility coefficients (ADC’s) for a

range of potential feed ingredients at different dietary inclusion levels. This was

achieved by applying an indirect method of determination (marker method; chromic

oxide) and collecting faecal material from snapper by passive settlement. The

digestibility methods we used for the preparation of diets and the collection of faeces

was standardised across all experiments in this study, and our results provide reliable

information on the digestibility of different feed ingredients by snapper. Similar

methods were used by Allan, Rowland, Parkinson, Stone & Jantrarotai (1999), to

investigate the digestibility of an extensive range of feed ingredients for silver perch

Bidyanus bidyanus (Allan, Parkinson, Booth, Stone, Rowland, Frances & Warner-

Smith 2000a). Individual feed ingredients were selected on the basis of their potential

for use in snapper diets, either because of an elevated protein or energy content, the

perceived ability to provide reasonable levels of essential amino or fatty acids or their

ability to provide functional qualities to experimental or commercial diets. Ingredients

investigated included those typically used in many carnivorous finfish feeds such as

fishmeal and fish oil, but also protein rich rendered by-product meals such as poultry

offal meal, meat meal and blood meals. In addition, the ADC’s of two forms of

soybean meal (expeller vs solvent extracted) were determined, as was the digestibility

of extruded wheat and fully gelatinised wheat starch (see Chapter 2 & 5).

The protein component of all individual feedstuffs we tested, with the

exception of meat meal, was extremely well digested. As expected, the organic matter,

protein, fat and gross energy from fishmeal or fish oil were highly digestible and these

ingredients will remain the benchmark by which other ingredients are judged (see

Chapter 2). Excluding ADC’s for meat meal, protein ADC’s for all other ingredients

ranged from 84.9 to 105.4%. In addition, the protein, fat or gross energy digestibility of


rendered animal meals were not affected by the inclusion levels we tested. The protein

digestibility of the meat meal was inferior to other protein sources, possibly due to

processing damage, and a protein ADC of between 62.2-65.3% was recorded.

Consequently, the gross energy ADC’s were also lower for this product. However, like

other animal meals, the protein, fat and gross energy digestibility of meat meal was not

affected by the inclusion levels tested in this study.

Carbohydrates offer a cheap source of energy in the diets of finfish and may

be of some benefit to carnivorous species such as snapper (Stone 2003). For this

reason, the digestibility of different levels of extruded wheat (see Chapter 2) or fully

gelatinised wheat starch was determined (see Chapter 5). Extruded or gelatinised

products were selected for evaluation because most modern feed mills employ extruder

technology to manufacture aquafeeds. This process invariably gelatinises the majority

of raw starch in these feeds, and therefore pre-extruded products serve as useful

substitutes for evaluation in experimental cold-pressed feeds. Extruded wheat contains

a low level of crude protein (172 g kg-1), but pregelatinised wheat starch is a pure starch

product, so serves only as a potential source of energy. Our results demonstrated that

protein from extruded wheat was well digested and independent of inclusion level,

however, the digestibility of organic matter and gross energy from both ingredients

varied inversely with inclusion level. We proposed that the reduction in digestibility of

starch as inclusion levels increased was related to the saturation of the carbohydrate

digestive mechanism, as reported for other species (Fernandez, Moyano, Diaz &

Martinez 2001; Stone 2003).

Rapid elevation in circulating levels of plasma glucose coupled with

prolonged hyperglycaemia following a glucose tolerance test (GTT) also indicated

snapper were intolerant of highly available forms of CHO (see Chapter 5) compared to

omnivorous species such as silver perch (Stone 2002). However, the uptake of more

complex forms of CHO (i.e. gelatinised wheat starch) from the digestive system of

snapper appeared to be more regulated and did not cause significant elevations in

plasma glucose concentration after 3 h (see Chapter 5). This data suggests that

utilisation of CHO by snapper, apart from being affected by the route of assimilation is

affected by the complexity of the CHO source, as described for other fish species

(Stone 2003).


7.1.3 Additivity of apparent digestibility coefficients for snapper

This thesis has demonstrated an inverse relationship between inclusion

level and the apparent digestibility of CHO by snapper. This outcome confirms that

gross energy and organic matter ADC’s for snapper fed ingredients that contain high

levels of starch based CHO are not additive (see Chapter 2 & 5). Consequently, it is

imperative to determine gross energy or nutrient ADC’s for these types of ingredients

over a practical range of inclusion levels before formulating experimental or

commercial aquafeeds.

Once determined, ingredient ADC’s for protein and energy were used

throughout this study to formulate experimental diets on a digestible protein (DP) and

digestible energy (DE) basis for snapper using a limited range of energy and nutrient

sources. This strategy required that the assumption of additivity hold true for the

ingredients supplying DP and DE in the experimental feeds we formulated. This

assumption was confirmed by the close approximation of formulated versus measured

DP and DE values of test diets fed to snapper in Chapter 3 (presented in more detail in

Table 7.1), despite the fact that these diets were composed of variable levels of

Table 7.1 Formulated versus measured digestible protein (g kg-1) and digestible energy (MJ kg-1) values of test diets used in Chapter 3.

Formulated1 Measured2 DP DE DP DE High energy diet series Diet 14 546.0 20.8 511.0±3.9 21.1±0.2 Diet 45 395.0 21.0 385.2±3.9 21.4±0.1 Diet 74 244.0 21.1 222.5±4.9 19.9±0.3 Mid energy diet series Diet 84 564.0 18.2 545.4±2.7 20.0±0.2 Diet 115 400.0 18.4 381.3±1.7 19.2±0.1 Diet 144 236.0 18.6 209.1±5.2 17.5±0.1 Low energy diet series Diet 154 473.0 15.2 472.6±1.5 16.9±0.1 Diet 185 342.0 15.3 331.0±1.1 16.2±0.0 Diet 214 211.0 15.6 190.4±2.5 14.3±0.2 Diet formulations presented in Booth, Allan & Anderson Chapter 3, Table 3.1 Abbreviations: DP=digestible protein; DE=digestible energy. 1Formulated DP and DE values based on data from an earlier study (Booth , Allan & Anderson 2005). 2 Based on digestibility experiment. Digestible value = ADC x dietary protein or dietary gross energy content. 4 Determined from 3 replicate tanks. 5 Determined from 2 replicate tanks.


fishmeal, extruded wheat and fish oil (see Chapter 3, Table 3.1). Although there were

minor differences between the formulated and measured DE values, differences

between DP values were greater. Regression of formulated versus measured DP values

indicated that the relationship was linear (i.e. measured DP value = 1.005(±0.0285) x

formulated DP value – 20.37(±11.34); R2=0.99), but that measured DP values were

consistently lower than formulated values by about 20 units. This is best explained by

the fact that a different batch of fishmeal was used in this study to that used to

determine the ADC of fishmeal in Chapter 2. Thus, the ADC of protein for the fishmeal

used in Chapter 3 is likely to be lower than that used in Chapter 2. However, the linear

nature of the relationship between formulated and measured DP values confirms the

additivity of protein ADCs for the ingredients used to formulate these diets.

7.1.4 Application of digestibility coefficients

The ingredient composition data and digestibility coefficients presented in

this study will complement the growing database of ADC’s for snapper fed alternative

Australian based ingredients (Table 7.2). These coefficients will improve the accuracy

of feed formulation and provide feed manufacturers with practical alternatives to

fishmeal. Besides the digestibility of ingredients determined in this study (see Chapter

2 & 5), these alternatives include wheat gluten and lupin kernal meals (Lupinus

angustifolius) (Glencross, Curnow, Hawkins, Kissil & Peterson 2003a), as well as

solvent extracted and expeller canola meals, canola protein concentrates and high

protein soybean meal (Glencross, Hawkins & Curnow 2004). Due to the high protein

requirements of snapper (see Chapter 3 & 4), future determination of ADC’s should

focus on high protein, low ash by-product meals derived from meat meals (ovine or

bovine) and other terrestrial animal meals. Cereal and oilseed based protein

concentrates (e.g. wheat, soy, canola) should also be investigated. However, for all

ingredients, inclusion contents will be determined by cost, particularly relevant to

fishmeal.

7.1.5 Estimating protein requirements

Historically, the quantification of nutrient or energy requirements for

different fish species has been undertaken using dose-response studies, where graded

levels of nutrients (protein, amino acids, fatty acids, minerals etc) or energy are fed and

changes in response variables such as weight gain, protein or energy deposition and


feed conversion ratio etc. are recorded for a suitable period. These relationships are

then studied by applying ANOVA or regression models (linear or quadratic functions;

bent-stick models; logistic functions; 4-SKM etc) to experimental data in order to

determine nutrient or energy requirements for maintenance and growth (Mercer 1982;

Mercer, Gustafson, Higbee, Geno, Schweisthal & Cole 1984; Shearer 2000; Allan,

Johnson, Booth & Stone 2001; Allan & Booth 2004). More recently, the application of

factorial models or D-optimal design strategies has become prevalent in fish nutrition

(Shearer 1995; Lupatsch, Kissil, Sklan & Pfeffer 1998 & 2001; Rouhonen, Koskela,

Vielma & Kettunen 2003). Irrespective of the approach selected, estimates of the

requirement are highly dependant on the chosen response criteria. The more specific

this response (e.g. protein deposition rather than weight gain), the better the estimate of

the true-requirement (Kevin Williams; personal communication).

Each of these approaches has particular strengths and weaknesses. For

example, the classical dose-response approach relies on the premise that the nutrient of

interest is the only variable limiting the expression of the response variable. This means

that if other nutrients or energy unknowingly become limiting, or interactions exist

between ingredients supplying the nutrient of interest, then the true-requirement can be

underestimated. Factorial models are based on the assumption that requirements equal

the sum of nutrients needed for maintenance, growth and reproductive outputs and

excretions (Lupatsch et al. 1998). This approach attempts to model the overall response

to nutrient intake. However, factorial models also estimate nutrient requirements using

a series of smaller dose-response studies and are therefore prone to the same problems

encountered in classical studies. In addition, the influence of such factors as genetic

make-up, stage of development, activity level and the nutrient density of diets on model

parameters is poorly understood (Kevin Williams; personal communication).

Notwithstanding these problems, provided data are accurate and similar specific

response variables are selected for investigation (e.g. protein deposition), differences

between requirements obtained using a dose response approach and those determined

using factorial models should be minor.

7.1.6 Digestible protein requirements and efficacy of high or low protein feeds

This thesis has confirmed that snapper, like the majority of marine

carnivores, has a high protein requirement. It has also demonstrated that weight gain

and protein deposition in juvenile snapper (30-90 g fish-1) is highly dependent on the


ratio of DP:DE. Application of a four parameter mathematical model for physiological

responses (4-SKM) developed by Mercer (1980 & 1982) to the data presented in

Chapter 3, indicated juvenile snapper require approximately 28 g DP MJ DE-1 to

optimise protein deposition and feed conversion ratio (see Chapter 3). This estimate is

almost identical to that reported for similar sized gilthead seabream Sparus aurata and

Australian snapper determined using factorial models (Lupatsch, Kissil, Sklan &

Pfeffer 1998 & 2001; Glencross & Lupatsch unpublished data). The close agreement

between our estimate (e.g. determined using a dose- response approach) and that of the

previous authors suggest that factorial models can be used as a basis for formulating

diets for fish outside the range we studied (> 90 g) (see Chapter 4). The agreement in

DP:DE requirement values and the possibility that snapper might have been protein

Table 7.2 Apparent digestibility coefficients for snapper fed alternative Australian based feed ingredients. Faeces collected by settlement methods.

Ingredient (inclusion level) Protein ADC Energy ADC (%) (%) (%) Fishmeal1 (42) 87.5 87.8 Wheat gluten1 (na) 102.0 84.3 Lupin seed meal (Gungarru)1 (30) 98.7 56.3 Canola meal (Solvent extracted)2 (30) 83.2 43.9 Canola meal (Expeller extracted)2 (30) 93.6 61.6 Canola protein concentrate2 (30) 52.6 73.7 Solvent extracted soybean meal2 (30) 79.2 58.3 Fishmeal3 (50) 94.3 99.2 Fish oil3 (15) na 100.5 Fish oil 3 (25) na 98.3 Extruded wheat3 (20) 100.6 80.5 Extruded wheat3 (30) 105.4 76.9 Extruded wheat3 (40) 100.1 74.4 Meat meal3 (30) 62.2 72.0 Meat meal3 (50) 65.3 70.5 Poultry meal3 (30) 84.9 91.4 Poultry meal3 (50) 86.9 91.4 Blood meal3 (15) 81.6 81.3 Haemoglobin powder meal3 (15) 95.1 79.5 Solvent extracted soybean meal3 (30) 87.2 66.8 Expeller extracted soybean meal3 (30) 90.7 64.3 Pregelatinised wheat starch4 (15) na 89.2 Pregelatinised wheat starch4 (25) na 73.9 Pregelatinised wheat starch4 (35) na 70.2 Pregelatinsed wheat starch4 (45) na 55.2 1 Data from Glencross, Curnow, Hawkins, Kissil & Peterson 2003a. 2 Data from Glencross, Hawkins & Curnow 2004. 3 Data from Booth, Allan & Anderson 2005 (i.e. Chapter 2). 4 Data from Chapter 5. Energy ADC’s presented are the average of ADC’s for small and large fish.


limited on high-energy, high-lipid diets formed the basis of the experimental design in

Chapter 4.

The major outcomes of experiments described in Chapter 3 and Chapter 4

indicate that for snapper fed to apparent satiation, feed intake is primarily governed by

the DE content of the diet, as reported for other species (NRC 1993). In this study we

have also shown that this is true regardless of whether DE is supplied in the form of

protein, lipid or CHO as supported by the similarity in relative feed intake for dietary

treatments with DE derived from different sources. Consequently, weight gain in

snapper is governed by the DP content of diets and the energy-regulated intake of DP

(see Chapter 3 & 4). Secondly, our data indicate that snapper perform better on high-

energy, high-protein diets provided a significant proportion of DE is in the form of

highly digestible protein. The appropriate level appears to be between 60% (Koshio

2002) and 68% of total dietary DE (see Chapter 4). The fact that feed conversion ratio

(FCR) in snapper from these experiments consistently improved as the level of DP in

diets was increased also suggests that protein may be the preferred energy source for

this species. Data from Chapter 4 did not provide unequivocal evidence that lipid or

CHO energy sources were able to spare protein for growth. However, wide variations

in the ratio of lipid and CHO did not significantly affect weight gain and performance

in snapper fed the majority of test diets containing similar levels of DP, indicating the

utilisation of both energy sources is similar for snapper when based on their DE values.

This result demonstrated that these two energy sources can be reliably exchanged

within the diet matrix provided inclusion levels and ratios are similar to those tested in

the present study.

In terms of weight gain and FCR, productivity of snapper could be

increased by using nutrient dense feeds (high protein), although these benefits must be

more fully assessed in terms of carcass composition before these specifications can be

unequivocally recommended.

7.1.7 Diet formulation and fishmeal replacement

Work presented in this thesis culminated in two experiments designed to

evaluate the potential of poultry offal meal, meat meal, blood meal and soybean meal to

partially replace fishmeal in diets for this species. All diets were formulated to contain

similar DP and DE levels according to the composition and ADC’s of individual feed

ingredients. In the semi-commercial pond experiment described in Chapter 6, diet


formulations were a compromise between nutritional requirements and the practicalities

of manufacturing an extruded aquafeed.

Our results have shown that snapper can tolerate high dietary levels of

poultry meal (360 g kg-1), meat meal (345 g kg-1) and soybean meal (420 g kg-1) before

performance or feed intake is unduly affected. In addition, the combinations of these

three ingredients (and blood meal) was able to effectively replace all but 160 g fishmeal

kg-1 in commercially manufactured diets for snapper (see Chapter 6), reducing the

ingredient cost of production for 1 kg of fish from $AUD1.26 to $AUD1.03 in diets

containing 600 or 160 g fishmeal kg-1, respectively. With the ever-increasing price of

fishmeal due to escalating demand and static world supply, the relative ingredient cost

savings reported by the current research will increase over time.

7.1.8 Implications of research for snapper industry

Assuming commercial production costs are equivalent for different diets,

use of ingredients similar to those tested in this study can reduce the levels of fishmeal

and thus the cost of snapper feeds. Due to the high protein requirements of snapper, the

fact that productivity improvements can be achieved by feeding high-protein feeds and

the increasing demand on existing fishmeal supplies, replacement of fishmeal in diets

for this species will be increasingly important in the future. In addition, because the

“formulation space” for other energy sources will be reduced in nutrient dense feeds,

the challenge will be to identify and test high protein ingredients that in combination

have a similar nutritional quality to fishmeal but at a lower cost. The paradox for

Australian snapper farmers is, that rather than lowering the cost of feeds, high-protein

nutrient dense feeds will inevitably be more costly than those formulated with a lower

nutrient specification. However, the increased growth and improved FCR of this

feeding strategy should make the use of more expensive, nutrient dense diets

economically sound.


7.2 CONCLUSIONS

Data presented in this thesis demonstrates that by applying a research

strategy based on determination of digestibility coefficients, an understanding of basic

nutrient requirements and ingredient utilisation, diets can be formulated to optimise

growth and minimise feed conversion ratio. Importantly, this approach also allows feed

manufacturers to choose between a range of alternative feed ingredients that in

combination can replace significant levels of fishmeal in the diets of Australian snapper

before weight gain and performance is negatively affected.

The major conclusions and findings of this research are:

Australian snapper are efficient at digesting the crude protein from a range of

ingredients including fishmeal, poultry offal meal, blood and haemoglobin

meals, solvent and expeller extracted soybean meals and extruded wheat. They

were less efficient at digesting the protein from a rendered meat meal by-

product, possibly because this particular meat meal was over processed.

The crude protein and gross energy ADC’s of poultry offal meal, meat meal and

extruded wheat were not affected by dietary inclusion level within the range

examined.

The gross energy and organic matter ADC’s of extruded wheat and

pregelatinised wheat starch were inversely related to inclusion level.

Gross energy ADC’s for snapper fed CHO based ingredients were not additive,

and ADC’s for these ingredients or those like them should be determined over a

wide range of inclusion levels before formulating experimental or commercial

diets.

Australian snapper were incapable of rapidly regulating their blood glucose

after an intra-peritoneal injection of glucose and remain hyperglycaemic for 18

h.


The optimum digestible protein (DP), digestible energy (DE) ratio of diets for

juvenile snapper weighing 30-90 g was determined to be 28 g DP MJ DE-1.

Dietary levels of extruded wheat and fish oil can be exchanged according to

their DE values in diets for snapper that provide 390-490 g DP kg-1 without

unduly compromising weight gain and performance.

Semi-commercial production diets for Australian snapper can be formulated

from a combination of alternative Australian based feed ingredients to replace

all but 160 g fish meal kg-1

181

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7.4 APPENDICES

investigation of the nutritional requirements ...in fulfillment of the requirements for the degree...

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