vens cappell 1985 aquacultural engineering

7/28/2019 Vens Cappell 1985 Aquacultural Engineering

1/17

Aqu aeul tura l Engineering 4 (1985) 33-49

M e t h o d i c a l S t u d i e s o n D i g e s t io n i n T r o u t . 1 . R e l i a b i li tyo f D i g e s t io n C o e f f ic i e n t s in R e l a t i o n t o M e t h o d s f o rF a e c e s C o l l e c t i o n

B. Vens-Cappell*Teichwirtschaftlicher Beispielsbetrieb, 8482 W611ershof, Bavaria,

West Germany

A B S T R A C TTw o me th o d s o r fa eces co ll ec ti o n w er e co mp a r ed w h en s t u d y in g d ig es ti o nin t rou t (7 8- 20 0g ind iv idua l weigh t ; 12-15C): (a) Faeces s t r ipped f romthe lower in tes t ine; (b ) faeca l pe l le t s f i l t ered con t inuous ly f rom waterusing an auto m ate d faece s collector. This apparatus co nsiste d o f a cylin-drica l tank wi th a fun ne l shaped bo t to m , f rom which the e f f luen t wa terwas drained ove r a rotatin g clo th fi l ter, separating the faee al pelle tsimm edia te ly f ro m water. The d iges t ion coe f f i c ien ts for energy and pro te ino f a co m mer c ia l f e ed a n d a n exp er imen ta l d i e t w er e d e t e r min ed a p p l yin gbo th m ethod s o f faeces co l lec t ion . Diges tion coe f f i c ien ts for pro te in o fthe exp er imen ta l ly com posed d ie t were 1 -2 .3% h igher for the f i l t eredfaeces than for the s t r ipped faeces (88 .6 -87 .3% ). The pro te in d iges t ioncoef f i c ien ts for the com merc ia l f ee d were abou t 5% h igher whe n faeceswere sampled by con t inu ed f i lt ra t ion . Resu l t s o b ta ined wi th the st ripp#zgm et ho d averaged 79.5%. The energy digest ion coe f f ic ients fo l low ed asimilar trend. I t was concluded that the s tr ipping method gives morereliable digestion coefficients.

1. INTRODUCTIONSince the introduction of the chromium indicator method into fishnutr itio n research (Nose, 1960) the pr oblem of collecting representativeunadulterated faeces samples has not yet been solved. A critical review33* Present address: Dorpsfelde 4, 2000 Hamburg, West Germany.Aquacul tural Engineering 0144-8609/85/$03.30 Elsevier Applied SciencePublishers Ltd, England, 1985. Printed in Great Britain


2/17

34 B . V e n s - C a p p e l lof methods for faeces collection has been given by Smith (1979). Afundamental difference exists between methods for faeces collectionfrom water and those for sampling faeces directly from the lowerintestine. Windell e t a l . (1978) removed faeces, which had settled in thetank, simply by using a hand net in intervals of 1-4 h. In the 'GuelphSystem' (Cho and Slinger, 1979) the effluent of the experimental fishtank passes a settling column, from which faeces are easily and quanti-tatively removed. French authors have tried to construct automaticfaeces samplers with the purpose of minimizing the contact of releasedfaeces with water (Possompes, 1973; Bergot, 1979; Choubert e t a l . ,1982). However, leaching of faecal material into the water seems to beinevitable with all of the methods mentioned above, resulting in highdigestion coefficients. This is the major reason why numerous authorshave tried to avoid the contact of faeces with water by developingsophisticated methods. Among these, the most simple one is to stripthe content of the lower intestine before its natural defaecation (Inabae t a l . , 1962; Nose, 1967; Possompes, 1973; Austreng, 1978; Windelle t a l . , 1978; Cho and Slinger, 1979). Faeces collected by stripping maybe contaminated by body slime, urine or sexual products. Therefore,faeces were also sampled by dissecting the fish and removing the faecesfrom a certain section of the intestine (Austreng, 1978; Windell e t a l . ,1978) or by sucking the lower intestine (Windell e t a l . , 1978).

Objections to all these methods of direct faeces sampling fromintestine relate to the fact that faecal material may be removed prior tothe completion of the natural retention time, thereby reducing thedigestion and absorption capacity and simulating poor digestibility.Hence, it follows that there is presently no method for faeces collectionwithout any inherent errors.Digestion coefficients obtained with faeces collected from water havebeen consistently higher as compared with those stripped or dissectedfrom the intestine. Differences between these two methods may exceed15% of the observed digestibility (Windell e t a l . , 1978). The questionstill remains unsolved which of the methods of faeces collection allowsthe least systematic error. The motivation to deal with the problems offaeces collection in this study was not at all a sense of methodicalpurism. The standardization of methods in digestion studies with fishis an indispensable precondition for the compilation of feed value tableswith respect to the formulation of least cost diets using linear program-ming techniques (Vens-Cappell, 1983).


3/17

Methodical studies on digestion in trout - 1 3 5T h e o b j e c t iv e o f t h e s t u d y p r e s e n t e d h e r e w a s a n e w a p p r o a c h t o th e

p r o b l e m . F o r t h is r e a s o n , d i g e s t i o n c o e f f i c i e n t s f o r p r o t e i n , e n e r g y a n da m i n o a c id s o f d i f f e r e n t t y p e s o f f e ed s w e r e c o m p a r e d a p p l y i n g t w om e t h o d s o f f a e c e s c o l l e c t io n : ( a ) s t r ip p i n g f a e c e s f r o m t h e l o w e ri n t e s t in e ; ( b ) f il te r in g f a e c e s c o n t i n u a l l y f r o m w a t e r u s i ng a f a e c e ss a m p l i n g a p p a r a t u s s im i l ar t o t h a t d e s c r i b e d b y B e r g o t ( 1 9 7 9 ) . I n a d d i -t i o n t h e i n f l u e n c e o f t i m e o f f a e c e s c o l l e c t i o n o n d i g e s t io n c o e f f i c i e n t sw a s s t u d i e d .

2 . M E T H O D S A N D M A T E R I A L S2 . 1 . E x p e r i m e n t a l procedures2.1.1. Faeces collection

2.1.1.1. Str ipping met hod . F i s h w e r e a n a e s t h e t i z e d w i t h 0 . 5 g 1, 1, l -t r i c h l o r i n e - 2 - m e t h y l - 2 - p r o p a n o l l it re -1 w a t e r , a n d a d h e r e n t w a t e r w a sr e m o v e d w i t h a t o w e l . W h i le t h e ri g ht h a n d k e p t t h e h e a d , f o r e f i n g e ra n d t h u m b o f t he l e f t h an d , e m b r a c i n g t h e b o d y , w e r e g e n t ly m o v e da l o n g t h e l a te r a l li ne s y s t e m t o w a r d s t h e a n u s . B y t h is m e t h o d s o m eu r i n e c o u l d b e p r e s s e d o u t , r e d u c i n g t h e ri sk o f l a te r f a e c e s c o n t a m i n a -t io n . T h e n , r e p e a t i n g t h e m o v e m e n t s im i la r ly , t h is t i m e w i t h p r e ss u r eo n t h e r e g i o n b e t w e e n a n a l f in a n d t h e a n u s , a f a e c e s c o l u m n o f 1 - 2 .5 c m( c o r r e s p o n d i n g t o t h e c o n t e n t o f t h e in t e st in e b e t w e e n a n u s a n d a na lf i n ) w a s s t r i p p e d i n t o a s l a n t b a s i n . W a t e r a n d u r i n e s t r i p p e d w i t h f a e c e sw e r e t h u s s e p a ra t e d i m m e d i a t e l y f r o m f a e ce s a n d c o u l d b e d e c a n t e deas i ly .

2.1.1.2. Cont inuo us f i l t rat ion meth od. F o r f a e c e s c o l l e c t i o n b y c o n -t i n u a l f il t r a t i o n , e x p e r i m e n t a l f is h w e r e t r a n s f e r r e d i n t o a c y l i n d r i c a lt a n k w i t h a f u n n e l s h a p e d b o t t o m . T w o ta n k s w i th c a p a c it ie s o f 6 0 0l it r e s a n d 1 0 0 li t re s w e r e u s e d . W a t e r f l o w r a t e t h r o u g h t h e t a n k s w a sk e p t b e t w e e n 1 0 - 1 5 l it re s m i n -1. A d r a in p i p e w a s a t t a c h e d t o th eb o t t o m . A b o u t h a l f o f t h e e f f l u e n t w a t e r p a s s ed t hi s tu b e . I t w a sd r a i n e d o v e r a s ie v e o r a c l o t h f i lt e r. T h e r e m a i n i n g e f f l u e n t v o l u m ew a s d r a i n e d t h r o u g h a f l o w o v e r p i p e ( F i g . 1 ). I n t h e i n i ti a l t r ia l f a e c a lp e l le t s c a r r ie d b y t h e e f f l u e n t w a t e r w e r e c a u g h t b y a s ie v e a n d p i c k e du p w i th t w e e z e r s i m m e d i a te l y . A s th is m e t h o d o f fa e c e s c o l le c t io n w a s


4/17

1 0

2

5

3

tO

4

3 6 B. Vens-Cappell

Fi g . 1 . Fa ece s co l l ec t i o n appa ra t us . 1 , L i d ; 2 , cy l ind r i ca l t ank , 1 00 l it r e s and 60 0l i t r e s , r e spec t i ve l y ; 3 , ove r - f l ow p i pe ; 4 , r o t a t i ng c l o t h f i l t e r ( 600 / am mesh s i ze ) ;5 , dr iv ing shaf t ; 6 , e lec t r ic motor wi th gear ing; 7 , e las t i c scraper ; 8 , bas in for col -

l ec t i ng f aeces ; 9 , s t and ; 10 , a f f l ux .


5/17

M e t h o d i c a l s t u d i e s o n d i g e s ti o n in t r o u t - 1 37e f f i c i e n t w i t h r e s p e c t t o a r a p i d s e p a r a t i o n o f w a t e r a n d f a e c e s b u tl a b o u r i n te n s i v e, f a e c e s fi l tr a t i o n w a s a u t o m a t e d a s s h o w n i n F ig . 1.T h e e f f l u e n t w a t e r w a s p a s s e d o v e r a c l o t h f i l te r o f 6 0 0 / a m m e s h s iz e .T h i s f i lt e r w a s r o t a t i n g o v e r t w o r o ll s a t a s p e e d o f 1 c m s-1 . Faeca lp e l l e ts c a u g h t b y t h e m o v i n g c l o t h f i lt e r w e r e s e p a r a t e d q u i c k l y f r o mt h e w a t e r a n d s c r a p e d i n t o a s t o r e - b a s i n a f t e r p a s si n g th e t o p r o ll .2 . 1 . 2 . R e a r i n g f a c i l i t i e sT h r e e e x p e r i m e n t s w e r e p e r f o r m e d in o rd e r to o p t im i z e t h e m e t h o d s o ff a e c e s c o l l e c t i o n b y c o n t i n u o u s f i l t ra t i o n .

1. I n t h e i n it ia l e x p e r i m e n t 2 2 0 t r o u t ( m e a n w e t w e i g h t 2 0 0 g ) w e r ek e p t i n a 1.6 m 3 t a n k ( f l o w r a t e a b o u t 2 0 l i t re s m i n - 1 a d d i t i o n a l l y a e r a t e d )a n d a c c u s t o m e d t o t h e e x p e r i m e n t a l d i e t H M f o r o n e w e e k . T h e w a t e rt e m p e r a t u r e w a s 1 3 C , a n d f is h w e r e fe d t w i c e a d a y a t 9 . 0 0 a n d 1 5 . 0 0h o u r s t o s a t i a ti o n ( a b o u t 2 % o f b o d y w e i g h t p e r d a y ) . A f t e r th e a d a p t i o na ll f i sh w e r e t r a n s f e r r e d t o t h e 6 0 0 l it r e f a e c e s c o l l e c t i o n t a n k f o rf a e c e s c o l l e c t i o n . F a e c e s w e r e c o l l e c t e d in s ix i n te r v a ls ( l a st in g 3 0 - 4 5r a in ; T a b l e 2 ) w i t h in 2 4 h . I m m e d i a t e l y b e f o r e e a c h s a m p l in g p e r io da s u b s a m p l e o f a b o u t 2 5 fi sh w e r e c a u g h t a n d a n a e s t h e t i z e d . F a e c e sw e r e s a m p l e d f r o m t h e s e f i s h b y t h e s t r i p p i n g m e t h o d . S t r i p p e d f i s hw e r e d i s c a r d e d . T h e f a e c e s o f f is h r e m a i n i n g i n t h e ta n k w e r e c o l l e c t e db y c o n t i n u o u s f i l t r a t i o n .

~' I n a s e c o n d t r ia l t h r e e c i r c u l a r t a n k s ( 4 0 0 li tr e s ; w a t e r f l o w r a t e8 l i tr e s m i n - 1) w e r e s t o c k e d w i t h 7 8 t r o u t ( a v e r a g e w e t w e i g h t 1 9 3 g )e a c h . F i sh w e r e f e d t h e e x p e r i m e n t a l d i e t H M o n c e a d a y a t 1 2 .0 0 h o u r s( 1 % b o d y w e i g h t a d a y ; t e m p e r a t u r e 1 5 C ) . A f t e r a n i ni ti al fe e d i n gp e r i o d o f o n e w e e k f is h w e r e t r a n s f e r r e d f r o m o n e c ir c u la r t a n k t o th el h e c es c o l l e c t i o n t a n k . F a e c e s w e r e f il te r e d o n t w o d a y s f r o m 1 3 . 0 0t o 1 6 . 0 0 h o u r s c o r r e s p o n d i n g t o 1 - 4 h a f t e r f e e d i n g , a n d f r o m 0 7 . 0 0t o 1 0 . 0 0 h o u r s c o r r e s p o n d i n g t o 1 9 - 2 2 h a f t e r f e e d i n g ( T a b l e 3 ) . O nt h e s e c o n d d a y f is h w e r e f e d i n t h e f a e c e s c o l l e c t i o n t a n k . P a r a l le l toe a c h f a e c e s c o l l e c t i o n p e r i o d t h e f a e c e s o f a b o u t 2 5 % o f t h e fi shr e m a i n i n g i n th e c i rc u l ar t a n k s w e r e s a m p l e d b y t h e s t r ip p i n g m e t h o d .S t r i p p e d f i s h w e r e a g a i n d i s c a r d e d .

3 . In t h e t h i r d t ri a l f iv e t a n k s ( v o l u m e 1 8 0 l it re s ; w a t e r f l o w r a t e5 l it re s m i n -1 ) w e r e s t o c k e d w i t h 5 5 t r o u t ( a ve r ag e w e t w e i g h t 9 1 g :w a t e r t e m p e r a t u r e 1 5 C ). F i s h w e r e a c c u s t o m e d f o r o n e w e e k t o t h ec o m m e r c i a l d i e t K 4 0 , w h i c h w a s f e d o n c e a d a y a t 1 2 . 0 0 h o u r s (2c:~b o d y w e i g h t ). F o r f a e c e s c o l l e c t i o n t h e t o t a l f is h s t o c k f r o m o n e t a n k


6/17

38 B. Vens-Cappellw a s t r a n s f e r r e d t o t h e 1 0 0 l it re f a e c e s c o l l e c t i o n ta n k . F a e c e s w e r ec o n t i n u o u s l y c o l l e c t e d i n f o u r i n te r v a ls w i t h i n 4 8 h a s d e s c r i b e d in t h ep r e v i o u s e x p e r i m e n t ( T a b l e 4 ) . P a r al le l t o e a c h c o l l e c t io n p e r i o d f a e c e sw a s s t r i p p e d f r o m t h e fi sh s t o c k o f o n e r e m a i n i n g t a n k . S t r i p p e d f is hw e r e d i s c a r d e d . A l l f a e c e s s a m p l e s w e r e d r i e d i n a v a c u u m d r y i n g o v e na t 7 5 C a n d s t o r e d i n a n e x s i c c a t o r f o r f u r t h e r a n a l y s e s .2 . 1 . 3 . E x p e r i m e n t a l d i e tsT h e t e s t d i e t H M ( c o m p o s i t i o n is d e p i c t e d in T a b l e 1) w a s s p e c i f ic a l lyd e v e l o p e d t o m e e t t h e f o l l o w i n g r e q u i r e m e n t s : ( a) f a ec e s s h o u l d r e m a i nc o h e s i v e in w a t e r , a n d ( b ) f a e c e s s h o u l d s e t t l e f a s t i n o r d e r t o f a c il i ta t ei ts r a p id s e p a r a t i o n f r o m w a t e r . T h i s w a s a c h i e v e d b y a d d i n g u n d i g e s t ib l eb a l la s t m a t e r i a ls ( c e l l u l o s e ) a n d a n o r g a n i c m a t t e r ( b o l u s a lb a ) .

A c o m m e r c i a l l y a v a il a bl e f e e d w a s u se d in a d d i t i o n t o th e t e s t d i e tw i t h a c o n t e n t o f 4 0 % c r u d e p r o t e i n , 7 . 5 % e t h e r e x t r a c t , 3% f ib r e a n d1 5% as h. A c c o r d i n g t o t h e i n f o r m a t i o n p r o v i d e d b y t h e p r o d u c e r 1 k gf e e d c o n t a i n e d 1 2 0 0 0 I U v i t a m i n A , 4 0 0 I U v i t a m i n D 3 a n d 6 0 m g

T A B L E 1Digestion Trials wi th T rout . C om posi t ion o f theExperim ental D iet HM Specifically Deve loped

to Produce Water-stable FaecesIngredients % in diet

Herring meal a 75.0Bolus alba 10-0Cellulose 6-7Water 3.5Lignin sulphonate 3.0Vitamin and mineral prem ix b 1.0Chromium(II l )ox ide 0 .8a 70% crude protein , 5-8% ether e xtract accord-ing to the prod ucer .

Deu tsche Vi lomix 12101, 1 kg prem ix con-tained 2 000 000 IU vi tamin A, 200 000 IUvitamin D3, 250 0 mg vitamin E, 65 00 mg M n,4 6 0 0 mg Fe , 3 6 0 0 mg Z n , 5 0 0 m g C u , 1 0 0 mg J .


7/17

M e t h o d i c a l s tu d i e s o n d i g es t io n i n t r o u t - 1 39v i ta m i n E . B o t h t h e e x p e r i m e n t a l a n d t h e c o m m e r c i a l f e e d s w e r e s u p p le -m e n t e d w i th 0 .8 % c h r o m i u m ( I I I ) o x i d e ( C r2 0 3) f o r t h e d e t e r m i n a t i o no f d ig e s t ib i l it y a n d w e r e t h e n p e l l e t e d t o 3 m m p e l le t s .

2.2. Analytical proceduresP r o t e i n c o n t e n t w a s c a l c u l a t e d f r o m K j e l d a h l - n i tr o g e n a c c o r d i n g too f f i c ia l m e t h o d s ( N a u m a n n a n d B a ss le r, 1 9 7 6 ). T h e e n e rg y c o n t e n t w a sd e t e r m i n e d w i t h a m i c r o - c a l o r i m e t e r ( I u l iu s P e t e r s , B e r li n ) a c c o r d i n gt o R o t h a n d B e c k e r ( 1 9 5 6 ) . A m i n o a c id s in s a m p l e s f r o m f e e d s a n df a e c e s w e r e d e t e r m i n e d a f t e r 2 4 -h h y d r o l y s i s w i t h 4 N - m e t h a n e s u l p h o n i ca c id in an a t m o s p h e r e o f n i tr o g e n a t 1 05 C u si n g a n a m i n o a c id a n a l y s e rB iC a l 2 0 0 ( H o r s t m a n n , 1 9 7 9 ). C h r o m i u m in f e e d s a n d f a e c es w a sd e t e r m i n e d p h o t o m e t r i c a l l y a f t e r a c id d i g e st io n ( P e t ry a nd R a p p ,1 9 7 0 / 7 1 ) u s in g d i p h e n y l c a r b a c i d r e a g e n t ( J o s h i d a , 1 9 6 0 ) .

T h e a p p a r e n t d i g e s t i b il i ty o f p r o t e i n , e n e r g y a n d a m i n o a c i d s w a sc a l c u l a t e d u s in g t h e f o r m u l a ( C a s t e ll a n d T i e w s , 1 9 8 0 ) :

% i n d i c a t o r in f e e d X % n u t r i e n t in f a e c e s )D a ( % ) = 1 0 0 X 1 % i n d i c a t o r in f a e c e s %. n u t r i e n t i n f e e d

2.3 . Statistical analysisD a t a w e r e s u b j e c t e d t o t w o - w a y v a r ia n c e a n a l y s e s a c c o r d i n g to t h ef o l l o w i n g m o d e l s :

x q = I .t + a~ + b~ + e~iw i t h x i i = m e a s u r e d v a l u e , ja = m e a n o f p o p u l a t i o n , a i = e f f e c t o f r o w s ,b i = e f f e c t o f c o l u m n s a n d e i / = r e s i d u e e r r o r , a n d

x i / k = I.t + a i + b i + ( a b ) i i + e i / kw i t h x i j k = m e a s u r e d v a l u e, /a = m e a n o f p o p u l a t i o n , a i = e f f e c t o fr o w s , b / = e f f e c t o f c o l um n s , ( a b ) i / = i n t e r a c t i o n a n d e o.k = r e s i d u ee r r o r. T h e e f f e c t s a r e a s s u m e d f i x e d , a n d th e e r ro r s a r e r a n d o m ( S a c h s ,1 9 7 4 ) .


8/17

40 B. Vens-Cappel l3 . R E S U L T S

T h e e x p e r i m e n t a l d i e t H M m e t a ll r e q u i r e m e n t s w i t h r e s p e c t t o w h i c hit h a d b e e n c o m p o s e d . F a e c a l p e ll e ts o b t a i n e d w e r e s o f t a n d s h o w e d as m o o t h s u r f a c e . T h e y w e r e c o h e s i v e i n w a t e r a n d s p h e r i c a l i n s h a p e ,a n d d i d n o t f al l a p a r t d u r i n g f i l tr a t i o n . A m e a n s e t t li n g s p e e d o f 9 .3c m s -1 w a s d e t e r m i n e d . A t a to t a l h e i g h t o f 1 .2 m o f t h e e x p e r i m e n t a lt a n k , l es s t h a n 15 s w e r e r e q u i r e d f o r t h e s e t t l i n g o f fa e c a l p e l l e ts .T h e a p p a r e n t p r o t e i n d i g e st io n c o e f f ic i e n t s f o r t h e e x p e r i m e n t a l d i e tH M a r e l i s te d i n T a b l e 2 , s t r a t if i e d a c c o r d i n g t o m e t h o d s a n d p e r i o d so f f a e c e s c o l l e c t io n . W i th 8 9 .5 % , t h e m e a n d i g e s ti o n c o e f f i c i e n t f o rp r o t e i n d e r i v e d f r o m c o n t i n u o u s l y f i l te r e d f a e ce s w a s s l ig h t ly b u t s ig ni-f i c a n tl y ( p < 0 . 0 5 ) h i g h e r w h e n c o m p a r e d w i t h t h e m e a n d ig e s ti o nc o e f f i c i e n t o b t a i n e d f r o m s t r i p p e d f a e c e s ( 8 8. 6 % ) . N o d i f f e r e n c e s w e r ef o u n d b e t w e e n d i g e st io n c o e f f ic i e n t s o b t a i n e d f r o m f a ec e s s a m p l es ind i f f e r e n t s a m p l i n g p e r i o d s .

T h e d a t a d e r i v e d f r o m t h e s e c o n d e x p e r i m e n t a l s e ri es ( T a b le 3 )c o r r e s p o n d e d t o t h o s e o b t a i n e d d u r in g th e f ir st o n e . T h e r e f o r e , a u t o -m a t i o n o f f a e c e s c o l l e c t i o n h a d n o i n f l u e n c e o n t h e re s u lt s. W i thf i l t e r e d f a e c e s a m e a n p r o t e i n d i g e s t i o n c o e f f i c i e n t o f 8 9.6% , w a sd e t e r m i n e d a s c o m p a r e d t o 8 7 .3 % a f t e r a p p l i c at i o n o f t h e st ri p p in gm e t h o d . T h e d i f f e r e n c e b e t w e e n t h e t w o w a s s i gn i fi c an t (p < 0 - 05 ) a n ds l ig h t ly g r e a t e r t h a n i n t h e f i rs t e x p e r i m e n t a l s er ie s. T h e m e a n d i g e s ti o nc o e f f i c i e n t s f o r e n e r g y w e r e 8 6 - 4% a n d 8 4.8 % ,, r e s p e c t iv e l y . T h e d i f f e r -e n c e w a s n o t s i g n i fi c a n t ( p > 0 .0 5 ) , h o w e v e r . S a m p l i n g t i m e h a d n oi n f l u e n c e o n t h e d i g e s t i o n c o e f f i c i e n t s f o r p r o t e i n a n d e n e r g y .

T h e d a il y c h r o m i u m i n t a k e r at e w a s 6 4 .5 m g C r k g- 1 f i s h . T h e i n t a k er a te is i d e n ti c a l w i t h t h e e x c r e t i o n r a t e , as c h r o m i u m ( I I I ) o x i d e is n o ta b s o r b e d b y t h e i n t e s t i n e . A s s u m i n g a c o n t i n u o u s d e f a e c a t i o n p r oc e s s,it c a n b e e s t i m a t e d t h a t 2 .7 m g c h r o m i u m w e r e e x c r e t e d b y 1 k g fis hh -1. T h e a m o u n t o f f a e c e s s t r ip p e d f r o m 1 k g f is h p e r p e r i o d a v e r a g e d1 75 m g ( - 1 9 m g s t a n d a r d d e v i a t i o n ) d r y m a t t e r , c o r r e s p o n d i n g to3 .2 m g c h r o m i u m . U n d e r n a t u r a l c o n d i t i o n s 1 k g f is h w o u l d h a vee x c r e t e d t hi s a m o u n t o f f a e ce s a n d c h r o m i u m , r e sp e c ti v e ly , w i t h i n7 1 r a in .

T h e d i g e st io n c o e f f i c i e n t s f o r p r o t e i n a n d e n e r g y o f t h e c o m m e r c i a lf e e d K 4 0 , w h i c h w a s f e d i n t h e t h i r d e x p e r i m e n t a l s e r i e s , a r e l i s t e d i nT a b l e 4 . T h e m e a n p r o t e i n d i g e s t io n c o e f f i c i e n t s ( 84 -6 % a f t e r c o n t i n u o u sf i l t r a ti o n a n d 7 9 -5 % a f t e r s t r i p p i n g ) d i f f e r e d s i g n i f i c a n tl y ( p < 0 . 0 0 1 )


9/17

M e t h o d i c a l s t u d i e s o n d i g e s t i o n i n t r o u t - - 1 41T A B L E 2

Apparent Digestion Coefficients for Crude Protein (DaCP) of the Experimental DietHM in Relation to Faeces Collection Method and Sampling Time

P e r io d T i m e a F a e c e s c o l le c t io n m e t h o d bC F , S T ,

D a C P ( % ) D a C P ( % )1 09.45-10.15 hours 89.6 87.92 13.30-14.00 hours 88.7 88.03 17.30-18.00 hours 89.3 89.14 21.30-22.00 hours 90.3 89.05 01.45-02.30 hours 89"8 88.56 07.00-07.30 hours 89.2 88-9

Mean 89.5 88.6Standard deviation -+ 0-6 +-0.5

T w o - w a y v a r ia n c e a n a ly s is , m o d e l w i t h o u t i n t er a c t io n :C a u se o f v a ri a nc e D F M Q FPeriods 5 0.39 2.1Methods (CF or ST) 1 2.52 13.64"Residue 5 0.185Total 11* Significant with p < 0.05.a Stripping of faeces was started immediately before the beginning of the continuousfiltration period.CF = continuous filtration of released faeces; ST = stripping faeces from lowerintestine.and so did the digestion c oeffic ients for energy (p < 0.01), which were73.7% and 68.0%, respectively. In addition a poor but significant(p < 0.01) influence of sampling time on protein digestion coefficientswas d ete cte d. Digestion coefficient s obt ain ed with faeces sampled19-22 h after feeding tende d to be 1-2% higher than those obtaine dwith faeces sampled 1-4 h af ter feeding.

The am ou nt of stripped faeces averaged 262 mg (-+ 29 mg standard


10/17

4 2 B. Vens-Cappell

T A B L E 3A p p a r e n t D i g e s ti o n C o e f f i c i e n ts f o r C r u d e P r o t e i n ( D a C P ) a n d E n e r g y ( D a E ) o f th eE x p e r i m e n t a l D i e t H M i n R e l a t io n t o F a e c e s C o l l e c t io n M e t h o d a n d S a m p l in g T i m e

Period Timea Faeces collection method ~CF ST

DaCe (%) DaE (%) DaCe (%) DaE (%)I 1 3 . 0 0 - 1 6 . 0 0 h o u r s 8 9 . 9 - 8 8 . 2 -2 0 7 . 0 0 - 1 0 . 0 0 h o u r s 8 9 . 7 - 8 6 . 9 -1 1 3 . 0 0 - 1 6 . 0 0 h o u r s 8 8 . 9 8 6 . 2 8 7 . 6 8 4 . 32 0 7 . 0 0 - 1 0 . 0 0 h o u r s 8 9 . 7 8 6 . 7 8 6 . 5 8 5 - 4

M e a n o f p e r i o d 1 8 9 . 4 - 8 7 - 9 -M e a n o f p e r i o d 2 8 9 -7 - 8 6 . 7 -T o t a l m e a n -+ s t a n d a r d d e v i a t i o n 8 9 .6 - + 0 . 4 8 6 .4 - + 0 . 4 8 7 . 3 - 0 . 8 8 4 .8 - + 0 . 8

Two-way variance analyses, model with and without interaction:D i g e s t i o n c o e f f i c i e n t s o f p r o t e i n D i g e s t io n c o e f f i c i e n t s o f e n e r g y

Cause of variance DF MQ F Cause of variance DF MQ FM e t h o d s ( C F o r S T ) 1 1 0 .1 2 5 5 3 . 3 * *P e r i o d s 1 0 - 4 0 5 2 .1I n t e r a c t i o n o f

m e t h o d s x p e r i o d s 1 1 . 12 5 5 . 9R e s i d u e 4 0 . 1 9T o t a l 7

M e t h o d s ( C F o r S T ) 1 2 .5 6 2 8 .2P e r i o d s 1 0 - 6 4 7 .1R e s i d u e 1 0 . 0 9T o t a l 3

* * S i g n i f i c a n t w i t h p < 0 - 0 1 .a S t r i p p i n g o f f a e c e s w a s s t a r t e d i m m e d i a t e l y a f t e r th e b e g i n n i n g o f th e c o n t i n u o u sf i l t r a ti o n p e r i o d .b C F = c o n t i n u o u s f i l t r a t io n ; S T = s t r ip p i n g .


11/17

M e t h o d i c a l s t u d i e s o n d i g e st io n i n t r o u t - 1 43

T A B L E 4Apparent Digestion Coefficients for Crude Protein (DaCP) and Energy (DaE) of theCommercial Feed K40 in Relation to Faeces Collection Method and Sampling Time

P e r i o d T i m e a F a e c e s c o l le c t io n m e t h o d bC F S T

D a C P ( % O a E ( % D a C P ( % D a E ( % )1 13.00-16.00 hours 84-4 74.4 78.3 66.32 07.00-10.00 hours 85.4 75.3 81.0 70.11 13.00-16.00 hours 84.1 70.8 78.3 66.52 07.00-10.00 hours 84.5 74.2 80.3 69.1

Mean of period 1 84.2 72.6 78.3 66.4Mean of period 2 85.0 74-8 80.6 69-6Total mean -+ standard deviation 84.6 _+ 0-6 73.7 -+ 2-0 79-5 -+ 1.4 68.0 -+ 1.9

T w o - w a y v a r i a n c e a n a l y s e s , m o d e l s w i t h i n te r a ct io n ."Digestion coefficients of protein Digestion coefficients of energy

C a u se o f v a ri an c e D F M Q F C a u se o f v a ri an c e M Q FMethods (CF or ST)PeriodsInteraction o fmethods x periodsResidueTotal

1 52.53 302-3*** Methods(CF or ST) 64.41 33.9**1 4.65 26.8** Periods 14.31 7.5

Interaction of1 1.36 7.8* methods periods 0.55 0.34 0.173 Residue 1.9017

*** Significant with p < 0 . 0 0 1 ; ** significant with p < 0 . 0 1 ; * significant withp < 0.05.a Stripping of faeces was started immediately after the beginning of the continuousfiltration period.b CF = continuous filtration; ST = stripping.


12/17

44 B. Vens-Cappelld e v i a t i o n ) k g 1 f i sh , c o r r e s p o n d i n g t o 3 . 4 m g C r k g 1 f is h . T h e d a i l yc h r o m i u m r a t e w a s 1 0 8- 4 m g C r k g 1 f is h . A s s u m i n g a c o n t i n u o u sd e f a e c a t i o n p r o c e ss , i t c a n b e e s t i m a t e d t h a t 1 k g fi sh e x c r e t e d , o na v e r a g e , 4 -5 m g C r h -1. T h u s , i t c a n b e c a l c u l a t e d t h a t t h e a m o u n t o fc h r o m i u m s t r i p p e d ( 3 .4 m g k g 1 fi sh ) a n d t h e c o r re s p o n d i n g a m o u n t o ff a e ce s , r e s p e c t iv e l y , w o u l d h a v e b e e n e x c r e t e d w i t h in 4 5 r a in u n d e rn a t u r a l c o n d i t i o n s . T h e f a e c a l p e l le t s o f t h e c o m m e r c i a l f e e d K 4 0 d is -i n e g r a t e d q u i c k l y in w a t e r . It w a s t h e r e f o r e n o t p o s s ib le t o m e a s u r e t h es e t tl i n g s p e e d c o r r e c t ly . W i th i n t w o d a y s o f c o n t i n u o u s f i lt r a ti o n o n l y4 0% o f th e c h r o m i u m a d m i n i s t e r e d h a d b e e n r e c o v e r e d . W h e n f e e di n gt h e e x p e r i m e n t a l d i e t H M , t h is r a te i n c r e a s e d t o 6 0% . I t m u s t b ee m p h a s i z e d , h o w e v e r , t h a t t h e o b j e c t iv e o f t h e f a e c e s c o l l e c t io n a p p a r a-t u s w a s n o t t o f i l te r f a e ce s q u a n t i t a t i v e l y b u t t o s e p a r a t e t h e m f r o mw a t e r i n t a c t a n d a s q u i c k l y a s p o s s ib l e. T h e r e f o r e , t h e g iv e n r e c o v e r yr a t e s r e p r e s e n t o n l y a r e la t iv e m e a s u r e o f w a t e r -s t a b i li t y o f f a e c es .

T h e i n f l u e n c e o f t h e m e t h o d o f f a e c e s c o l l e c t io n o n t h e d i g e s ti o nc o e f f i c i e n t s o f a m i n o a c id s is s u m m a r i z e d i n T a b l e 5 . T h e d e t e r m i n a -t i o n o f d i g e s ti b il it y o f a m i n o a c id s w a s p e r f o r m e d w i t h th e s a m p l et a k e n b e t w e e n 0 7 . 0 0 a n d 1 0 .0 0 h o u r s o n t h e s e c o n d d a y ( T a b le 4 ). T h ed i g e s t i o n c o e f f i c i e n t s o b t a i n e d f o r t h e s u m o f a m i n o a c i d s w e r e 87 -4 %( f a e c e s f i l t r a t i o n ) a n d 8 5 . 6 % ( f a e c e s s tr i p p in g ) . T h e s e v a lu e s d i f f e r e d l es st h a n t h o s e f o r c r u d e p r o t e i n ( 8 4 .5 a n d 8 0 .3 % , r e s p e c ti v e l y ). A n e x c e p -t i o n w a s f o u n d f o r t h e a p p a r e n t d i g e s t io n c o e f f i c i e n t s o f a s p a rt ic ac i d ,w h i c h d i f f e r e d c o n s i d e r a b l y b e t w e e n 8 6 .7 % ( f a e c e s f i l tr a t i o n ) a n d7 8 . 6 % ( f a e c e s s t r ip p i n g ) . T h e t w o - w a y v a r i a n c e a n a l y s i s r e v e a l e d si gn i-f i c a n t d i f f e r e n c e s ( p ~ 0 .0 1 ) b e t w e e n t h e m e a n d i g e s ti o n c o e f f i c i e n t sf o r i n d i v i d u a l a m i n o a c i d s . T h e s a m e h o l d s f o r t h e a v e r a g e d i g e s t i o nc o e f f i c i e n t s fo r a m i n o a c id s o b t a i n e d w h e n u s in g t h e t w o d i f f e r e n tf a ec e s c o l le c t io n m e t h o d s .

4 . D I S C U S S I O NP r e vi o u s e x p e r i m e n t s p e r f o r m e d b y d i f f e r e n t a u t h o r s ( P o ss o m p e s ,1 9 7 3 ; W i n d e l l e t a l . , 1 9 7 8 ; C h o a n d S l in g e r, 1 9 7 9 ) r e v e a l e d , a s w e l l a st h e s t u d y p r e s e n t e d h e r e , t h a t f a e c e s c o l l e c t i o n f r o m w a t e r r e s u l t e d i nh i g h e r d i g e s t i o n c o e f f i c i e n t s as c o m p a r e d t o f a e c e s c o l l e c t i o n d i r e c tl yf r o m t h e i n t e s t in e . T h r e e h y p o t h e s e s ha v e t o b e t a k e n i n t o c o n s i d e r a -t i o n i n o r d e r t o e x p l a i n t h e s e r e s u l t s :

1. T h e f a e c e s f i l t e re d f r o m w a t e r is l e a c h e d w h e r e b y a n i n c r e a s e dd i g e s t i b i li t y i s s i m u l a t e d .


13/17

M e t h o d i c a l s tu d i e s o n d i g e s t io n i n t r o u t - 1 45T A B L E 5

Influence of Faeces Collection Method a on theApparent Digestion Coefficients for Amino Acids andProtein of the Commercial Feed K40

A m i n o a c id s A p p a r e n t d i ge s ti o n c o e f f ic i e n t sC F S T

Asp 86.7 78-6Thr 86.0 83-9Ser 87.0 83-6Glu 90.0 88.2Pro 86.4 84.6Gly 82.6 82.7Ala 86.4 86.5Cys 90.3 86-6Val 87.6 86.4Met 85.6 8 5 . 0Ile 87.7 86.4Leu 87-7 86.6Tyr 84.2 83-4Phe 86.8 87.2Lys 88.8 87.0His 86.1 83-7Arg 90.4 90-2

Sum of amino acids 87.4 85.6Crude protein 84.5 80.3

T w o - w a y v a r i a nc e a n a ly s is , m o d e l w i t h o u t i n te r a c ti o n :C a u se o f v a ri an c e D F M Q F

Amino acids 16 9.06 4.5**Methods (CF or ST) 1 25.9 12.9"*Residue 16 2.01Total 33** Significant with p < 0.01.a CF = continuous filtration; ST = stripping.


14/17

46 B. Vens-Cappell2. The stripped faeces contains residues of not yet digested or

absorbed nutrien ts resulting in an underestimat ion of digestibility.3. The stripped faeces contains traces of urine, slime, serum, epithel

of intestine and, eventually, sexual products, artefacts, which alsosimulate a decreased digestibility.

The results presented in this paper indicate that the first hypothesispossesses the greatest power of explanation without disproving com-pletely the two other hypotheses. When the experimental diet HM wasfed, faeces leaching could evidently be minimized due to the water-stability of the faeces and their high settling speed. In consequence thedigestion coefficients for protein and energy derived from faeces col-lected by con tinuous filtration and by stripping differed only by 1-2.5%.In contrast, the commercial feed K40 produced a faeces of poor coher-ence in water. Already a contact with water of 20-30 s (speed of sedi-mentation could not be determined exactly) resulted in a considerableincrease in the measured prote in and energy digestion coefficients of atleast 5% due to leaching of faecal nitrogen and energy into water. It isevident that the diverging results obtained with the experimental andcommercial diets cannot be interpreted adequately using hypotheses 2and 3. Adultera tions of stripped faeces by yet undigested materials andartefacts like urine, slime, etc., must have occurred with both theexperimental and the commercial diets.

Accordingly the decrease of the measured digestion coefficient dueto such adulterations should be independent of the type of feed. Asthis is not true, it must be concluded that leaching of faeces collectedfrom water resulted in an overestimation of digestibility rather thanthat adulterations of stripped faeces caused an underestimation ofdigestion coefficients.The reliability of faeces collection from water basically depends onthe question: is there an important fraction of soluble materials innaturally defaecated faeces? If that is true, a contact of faeces withwater of a few seconds would be sufficient to leach this soluble frac-tion. Possompes (1973), who studied the kinetics of leaching for faecalnitrogen, could demonst rate tha t the crude protein cont ent of a strippedfaeces sample decreased from 35 to 20% when it was exposed to waterfor 5 rain. The crude pro tein con ten t of filtered faeces samples decreasedfrom 22.8 to 16.3% when the time of wate r contact of the faeces wasincreased from 5 to 60 rain. Accordingly, Windell et al. (1978) demon-strated that most leaching of faecal materials occurred within the first


15/17


16/17

48 B. Vens-Cappellp r i o r t o s t r ip p i n g ; ( b ) t h e a m o u n t o f f a e c e s s t r i p p e d s h o u l d b e c o n t r o l l e d .A c c o r d i n g t o t h e r e s u lt s o f t h e s t u d y p r e s e n t e d h e r e , t h e q u a n t i t y o fs t r ip p e d f a e c es s h o u ld b e l i m i t e d t o t h e v o l u m e e x c r e t e d u n d e r n a tu r a lc o n d i t i o n s w i t h in a b o u t 1 h .

T h e c o n t i n u o u s f i l tr a t io n m e t h o d s e e m s to b e t h e m o s t r el ia b le ,a m o n g s t a ll m e t h o d s t e s t e d , w h e n c o l l e c ti n g f a e c es f r o m w a t e r . T h et e c h n i q u e m i n i m i z e s t h e c o n t a c t ti m e w i t h w a t e r d o w n t o s o m e 10 s.T h e d i g e s ti o n c o e f f i c ie n t s o b t a i n e d w i t h t h e s t ri p p in g m e t h o d a s w e l l a st h e c o n t i n u o u s f i l t r a t io n m e t h o d d i f f e r b y 1 - 2 .5 % , i f fa e c a l p e l le t s a r es t ab l e i n t h e w a t e r a f t e r d e f a e c a t i o n . G r e a t e r d i f f e r e n c e s i n d i g e s t io nc o e f f i c i e n t s a re d u e t o d i s i n t e g r a t i o n o f f a e ca l p e l le t s f i l t e re d f r o mw a t e r . I n t h e s e c a se s v a l u es s h o u l d b e o b t a i n e d b y u s i n g t h e s t r i p p in gm e t h o d .

A C K N O W L E D G E M E N T ST h e a u t h o r w i s h e s to e x p r e s s h i s g r a t i t u d e t o : P r o f e s s o r H .-J . H o r s t m a n n ,I n s t i t u t f ti r P h y s i o l o g i s c h e C h e m i e d e r U n i v er s if fi t E r ! a n g e n - N f i rn b e r g ,f o r p e r f o r m i n g t h e a m i n o a c i d a n a l y s e s ; M r M e h l e r, M e l a- S il v er -C u p , f o rs u p p l y i n g t h e e x p e r i m e n t a l d i et s; D r R e i c h le , F a c h b e r a t u n g f fi r F i s c h e re id e s B e z i rk s O b e r p f a l z , f o r m a t e r i a l a n d f i n a n c ia l s u p p o r t ; a n d P r o f e s s o rD r R o s e n t h a l , B i o l o g is c h e A n s t a l t H e l g o l a n d , H a m b u r g , f o r r e v i e w i n gt h i s m a n u s c r i p t .

R E F E R E N C E SAustreng, E. (1978). Digestibility dete rm inatio n in fish using chrom ic oxide markingand analysis of contents f rom different segments of the gastrointest inal t ract .

Aquaculture, 1 3 ,2 6 5 -7 2 .Bergot, F. (197 9). Problem es particulieres p os6 s par l'utilisation des glucides chezla truite arc-en-ciel. Annales de la nutrition et de l'alimentation, 3 3 , 2 4 7 - 5 7 .Castell, J. D. & Tiews, K. (eds) (1980). Report of the EIFAC, IUNS and ICESWorking Group on Standardization of Methodology in Fish Nutrition Research,Hamburg. (EIFAC Technical Paper No. 36.)Cho, C. Y. & Slinger, S. J. (1979). A ppa rent digestibility m eas ure m ent in feedstuff sfor rainbow trout. In: Finfish Nutrition and Fishfeed Technology. Proceedingsof a World Symposium, Vol. 2, eds J. E. Halver and K. Tiews, HeenemannVerlagsgese llschaft, Berlin.


17/17

M ethod ical s tudies on digest ion in trout - 1 49Chouber t , G. , De La Noue , J . & Luquet , P . (1982) . Diges t ib i l i ty in f i sh : improved

device fo r the au to m at ic co l lec t ion o f feces. A q u a cu l t u r e , 29 (1 -2 ) , 185-9 .H ors tm ann , H. -J . (1979) . A p rec ise m eth od fo r the qua n t i t a t io n o f p ro te ins t ak ingin to acco u n t t h e i r am in o ac id co m p o s i t i o n . A n a ly t i ca l B io ch emi s t r y , 96 , 130-8 .Inaba , D. , O g ino , C . , Tak am atsu , C . , Sugam o, S . & Hata , H. (1962) . Diges t ib il i ty o f

d ie ta ry com pon en ts in f i shes . I . Diges t ib i l ity o f d ie ta ry p ro te ins in ra inbowt ro u t . Bull. Jpn. Soc. Sci. Fish. , 28 (3 ) , 367-71 .

J o s h id a , M . (1 9 6 0 ) . R ap id co lo r im e t r i c d e t e rm in a t i o n o f ch ro m ic o xid e wi thd ipheny lcarbac id . Bu l l Na t . Ins t . Agr icu lt . Sc iences Japan , 19, 127-32.

Naumann , K. & Bass le r , R . (1976) . Ha ndbu ch der landw irtschaf t l ichen Versuchs-und Un tersuchungsm ethod ik (Methoclenbuch ). Die chemische U ntersuchung yonF u t t e r m i t t e l n , Verlag J . N eu m an n -Neu d am m , B e rl in .Nose , T . (1960) . On the e f fec t ive va lue o f f reshw ater g reen a lgae, Chlorella elip-soidea, as a nutr i t ive source to gold-fish . Bu l l Freshw ater F ish. Res . Lab.{ T o k y o ) , 10, 1-10.

Nose , T . (1967) . On the metabo l ic feca l n i t rogen in young ra inbow t rou t . Bull.Freshw ater F ish. Res . Lab . ( To ky o) , 17 , 97-105 .

Pe t ry , H . & R ap p , W . (1 9 7 0 /7 1 ) . Z u r P ro b l em a t ik d e r C h ro m o x id b es t im m u n g i nVerd au u n g s v e r s u ch en . Zeitschr . Tierern. Fu t ter m it te lkd . , 27 , 181-9 .

Possompes , P . P . (1973) . In f luence de la t empera tu re su r l es beso ins en p ro t6 inesle transit alimentaire et la digestibili t~ chez la truit arc-en-ciel Salmo gairdneriRic hard son. These de 3e cyc le, Univers it~ de Paris, VI.Ro th , S . & Becker , F . (1956) . Kalorim etr ische M ethod en. Verfahrens- und Me~-kun de der Na turwissenscha f ten , 12 , F. Vieweg und Sohn , Braunschweig .

Sachs , L . (1974) . Ang ew and te S ta t i s t i k . 4 . Neu bearbe i te te un d erwe i ter te Au f lage ,Springer-Verlag, Berl in , He idelberg , New Y ork.

Sm i th , R . R . (1979) . M ethods fo r de te rm ina t ion o f d iges t ib il i ty and m etabo l izab leenergy o f feeds tu f fs fo r f in f i sh . In : Fin f i sh Nu tr i t ion and F ish eed Techno logy .Proceed ings o f a Wor ld Sympos ium, Vol. 2 , eds J . E . Halver and R. Tiews,Heenemann Verlagsgesel lschaft , Berl in .

Sm i th , R . R . , Pe te rson , M. C . & Al l red , A. C . (1980) . E ffe c t o f leach ing on appa ren td iges t ion coeff ic ien ts o f feeds tu f fs fo r sa lmonids . Prog . F ish -Cul t . , 42 (4 ) ,195-9 .

Vens-Cappel l, B . (1983) . Exper im en te l le Erprobung e ines K onze p ts der l inearenOp t im ie ru n g y o n T ro ck en m is ch fu t t e r f f ir d ie R eg en b o g en fo rel le (Salm o gairdneriRicha rdson) au f der Basi s der verdau l ichen N/ ih rs to f fe . Thes i s, Ham burg .

W indell , J . T .~ Fo l tz , W . J . W . & Sarok on , J . A. (1978) . M ethods o f feca l co l lec t ionand nu t r ien t l each ing in d iges t ib i l ity s tud ies . Prog. Fish-Cult. , 40 (2 ) , 51 -5 .

vens cappell 1985 aquacultural engineering

Documents