Download - Biofloc Yoram Avnimelech 2
FEEDING OF TILAPIA ON MICROBIAL FLOCS
Yoram AvnimelechTechnion, Israel Inst of Technology
Figure 1
Figure 2
Recycled protein
Data on feed protein utilization
� Conventional fish, shrimp ponds 20-25%� ASP Tilapia ponds (Avnimelech) 45%� ASP Shrimp ponds (McIntosh) 45%� Closed shrimp tanks (Velasco) 63%
� ASP shrimp ponds, 15N studyMichele Burford et al. 18-29% of total N consumption
Typical Biomass:Intensive shrimp ponds 1-2 kg/m2
Intensive fish ponds 10 – 50 kg/m2
Objectives
� Evaluate uptake of microbial flocs by fish.
� Follow utilization of microbial protein by fish
� Develop predictive tools
Pacific Aqua farmsImperial valley CA
Pond Characteristics
1313Aeration, hp/1000 sq.m
2030-35% protein in feed
620% Daily Water exchange
ASPConventional
Tanks: 800 l20 fish, 107 g each15N added, + 150 g starch To incorporate all TAN in microbial cells
2 Experimental phases:
� 1. No feed added for 6 days.Only food source – microbial flocs
2. Feed added (6 days in Pacific, 9 days in Dor, Israel)
Results: a. Floc volume
Results: Floc volume
0
5
10
15
20
25
30
35
40
45
-5 0 5 10 15Days from stocking
floc
volu
me,
ml
FV = 31 – 1.714 t, R2 = 0.686,
Floc Plug contained 1.4% dry solidsDaily uptake per fish = 1.15g
0
100
200
300
400
500
600
700
TSS,
mg/
l
1 3 6 9 12
Days
Changes of TSS, Total suspended solids with time-20 mg/l day in no fed phaseDaily uptake per fish, 0.954 g
0.020.040.060.080.0
100.0120.0140.0160.0180.0
0 2 4 6 8 10 12 14daysm
gC/l
Changes of suspended carbon with timeC = 168 – 6.61 t R2 = 0.986 Daily uptake by fish 0.59 g carbon
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0 2 4 6 8 10 12 14days
mgN
/l
Changes of suspended nitrogen N = 24.8 – 0.868 t R2 = 0.987 Daily uptake by fish = 0.039 g N
= 0.25 g protein
Daily decrease of TSS, floc volume, suspended carbon and nitrogen,
during the no – feed period.
1.0341.181.1540.954Daily uptake by fish as equivalent SS (g/fish)
23.526.924.320Equivalent dry SS change (mg/l)
0.87 mg/l6.61 mg/l1.74 ml/l20 mg/lDaily measured change
NitrogenCarbonFloc Volume
TSS
Bonus: 15N Results
15N enrichment (%) of suspended matter in the Pacific Aquafarm tanks.
y = -0.0465x + 1.5942R2 = 0.9728
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0 2 4 6 8 10 12 14
Days
%15
N
15N enrichment (%) of suspended matter in the Dor tanks.
y = -0.048x + 1.65R2 = 0.9455
0.00.20.40.60.81.01.21.41.61.82.0
0.0 5.0 10.0 15.0 20.0 25.0
Days
15n
enri
chm
ent
%
What are the reasons for the decline of 15N enrichment?
� 1. Uptake of 15N enriched microbial protein.
� 2. Excretion of TAN originating in “old”, un-tagged fish protein
15N percentage in fish sampledin the Pacific Aquafarm experiment
15N, Fish, California
0.30
0.32
0.34
0.36
0.38
0.40
0.42
0.44
0.46
0 2 4 6 8 10 12 14Days
15N
enric
hmen
t,%
15N percentage in fish sampled in the Dor experiment
15 n enrichment, Fish, Dor
0.30
0.32
0.34
0.36
0.38
0.40
0.42
0.44
0.46
0.48
0.50
0 5 10 15 20 25
Days
15N
enric
hmen
t,%
Calculation of N uptake and excretion
� Assumptions:� Two processes:� 1. Uptake of suspended N (flocs, feed)� 2. Excretion of TAN� NH3 volatilization, denitrification, negligible.
∆15Nw (mg /l) = ∆ 15Nw (%) x Nt (mg /l)
and:Net Nt uptake (mg /l) =
= ∆ 15N (mg /1)/∆15Nw(%)
Net Nt Uptake in Pacific was found to be44.4 + 14.8 mg N/ fish * day for both non-fed and fed phases(From balance approach, N uptakeWas 39 mgN/fish * day
The difference between uptake and accumulation by fish
A certain fraction of N taken up is excreted.Nt accumulated= Nt up – Nt ex
In previous calculations, both those using material balances and those using 15N,
The net uptake (accumulation) were obtained.Using the 15 N technique, it is possible to
evaluate amount of excreted N.
Results
� During the no-feed period in Pacific expt.,� N uptake was 25 mg N/day * fish.� N excretion 4.4 mg N/day * fish, � i.e. excretion was 15% of uptake, � Compared to ~ 70% for whole pond
balances.� Is it since microbial protein is a better
diet?? More work is needed
Conclusions (1)
� 1. It was shown that microbial flocs are effectively utilized by tilapia. Consistent results were obtained using a number of independent measures: Floc volume, changes in time of TSS, C & N in the water and changes with time of 15N in water & fish.
Conclusion (2)
� 2. for a tilapia pond with ca 25 kg fish/m3 and floc volume of ~ 30 ml/m3, about 50% of feed and protein requirement were supplied by the microbial flocs.
� 3. Volumetric concentration of flocs (FV) is an easily obtained indicator of floc feeding potential. e.g., 5 ml/l FV is equivalent to 700 kg feed/ha.
Conclusion (3)
� 4. It seems that flocs harvesting is independent of feeding.
� 5. Floc harvesting probably follows:� Floc Harvesting = VFC * FS * K(fish)� Where VFC is floc volumetric
concentration, FS, properties of flocs (size, charge, adherence..) and K (fish), prperty of fish (species, size, etc)
Conclusion (4)
� 6. It is possible that microbial protein has a higher availability than feed protein.
� 7 This topic needs and deserves more research
� Thanks for your attention� [email protected]