Dissertation submitted by Shri. C. R E G U N A T H A N in partial fulfilm ent for the Degree o f Master of Science (Mariculture) of the
Cochin University of Science and Technology
December 1992
Post-G raduate Programme in M ariculture
CENTRAL M A R I N E FISHERIES R E S E A R C H INSTITUTE Cochin - 682 031
AccestfiM Ew ^ . . ...——
Ctess H« ...,..^ ...^ .2 i!....
This is to certify that this dissertation is a bonafide record of work carried out by Shri. C . REGUNATHAN under m y supervision and that no part thereof has been presented before for any other degree.
K . P R A B H A K A R A N N A I R SCIENTIST-SG
C E N T R A L M A R I N E F IS H E R IE S R E S E A R C H IN S T IT U T E
C O C H I N .
C o u n t e r s ig n e d by:
> IR E C T O R
C E N T R A L M A R I N E F IS H E R IE S R E S E A R C H IN S T IT U T E
C O C H I N .
Page No.
P R E F A C E 1 - 3
IN T R O D U C T IO N 4 - 7
M A T E R IA L S AND M E T H O D S 8 - 2 3
R E S U L T S . 24 - 59
D IS C U SS IO N 60 - 65
S U M M A R Y 66 - 69
R E F E R E N C E S 70 - 78
W it h the situation that the production by c ap tu re fisheries has reached o r is reaching a state of m axim um exploitation, it is rightly presumed that there w ould b e a decline in production. In context with this situation, aquaculture h a s been found to be a supplementary source to cater to the increasing world needs for fisheries p r o d u c t s . T h is has led to th e upsurge in aquaculture p rac tic es in many countries including India.
A p a r t from satisfying the national food needs, th e fishery products have b e e n contributing greatly to the foreign exchange earnings of many countries, w ith the s h r i m p s taking th e lion's s h a r e . Because of the increasing dem and for s h r im p in the w o r l d market and because of its v e ry high e xp o rt value, sh rim p culture has a d v a n c e d to a great extent, accounting for about 28% of world s h r im p production (in 1 9 9 1 ). I n d i a , with a culture area of 6 5 , 0 0 0 ha, accounts for about 5% of total production.
P r o p e r formulation of nutritious feeds with h i g h conversion rates is now one of the major priority areas in aquaculture r e s e a r c h , as the feed takes up ev e n 50% of the total cost. A s the efficiency of the com pounded feGd d e p e n d s to a great extent on its ingredients and a s the cost of the feed p l a y s a vital role in the overall economics of the culture operatio ns, the search for more su itab le and economically viable food source, is still continuing vig o ro u sly .
this aspect in v ie w , the present study h a s been carried out using the b la c k clam V illorita cyprinoides (G r a y ) as fe e d component for the Indian w h ite prawn P e n a e u s indicus ( H . Milne E d w a r d s J which is one of the foremost
cultivated species in In d ia .
T h e objectives of the present investigation are the following:
1) To evaluate the p r o x im a te composition of clam m eal with a v i e w to use it as supplementary protein source in prawn f e e d ;
2) To stud y the effect of different le v e ls of clam m eal in somi-purified
I
diets on growth, p rotein efficiency ratio and food conversion ratio to determ ine its optim um Inclusion le v e l for Penaeus i n d i c u s ,
3) To a s s e s the overall biological v a lu e of clam protein through nitrogen balance studies.
I w i s h to e x p r e s s m y immense gratitude to S h r i . K . P ra b h a k a ra n Nair, Sc ie n tist, Molluscan Fisheries D i v is i o n , Central Marino F is h e r ie s Research Institute, u n d e r w h o s e guidance and supervision this w ork h a s been c arried out. I am grateful to D r . P . S . P . R . J a m e s , Director, Central Marine F i s h e r ie s Research Institute, for p rovid in g all fac ilitie s . T h is w ork would not h a v e been com pleted without th e timely h e lp , guidance and a d v i c e
Smt. V . K r ip a , Scientist, S h ri. M a t h e w Joseph, T ech n ical A ssistant, S h ri. A . Nandakumar, Technical Assistant and S h r i . P . R a g h a v a n , p h o to g rap h e r. I am also thankful to the adm inistrative staff of the Institute. P . G . P . M . office staff in p a rtic u lar, and too m y dear classmates for the v a lu a b le help.
T h e aw a rd of Jun io r Research F e llo w s h ip by th e Indian Council of Agricultural Research d u rin g the Post Graduate Program ine is gratefully a c k n o w le d g e d .
T h o u g h pririltive methods of p r a w n culture h a v e been practisrri for c m t u r ie s in India and oth er Asian countries, only after the Second W orld War and n e e d for increased production of protein-food w a s felt and this proirpted the revival pjid inproveirent of old culture p r a c t ic e s , supplerrented wit!) nev; culture te c h n iq u e s. Among a ll the aquaculture products, p r a w n is the most lucrative comirodity earning large amount o f foreign exchanpf?.
India’ s p r a w n production b y culture in 1991 was 3 5 , 0 0 0 rretric tons (Rcflcnberry, 1992) and the money earned b y exporting p r a w n in 1990-1991 was about R s , 6 8 .3 3 crores ( M P E D A , 1 9 9 2 ),
I
In the high- density shrimp culture s y s t e m s , complete or supplem entary feeding b e c o m e s inevitable for better farm production. Feed constitutes one of the m.ajor fractions of the operational costs in aquaculture, accounting for 25-50% of the total production cost d e p e n d in g upon the type and efficiency of the culture operation. Considerable w o r k has been done to understand the nutritional requirements of praw ns, particularly in the Indian w h it e prawn P e n a e u s indicus b y several w o r k e r s in recent y e a r s (All, 1 9 8 2 a , 1982b ; J y o t h y , 1983; A li an d Sivadas, 1 9 8 3 ; Thom as, 1 9 8 5 ; Gopal, 1 9 8 6 ; Chandge, 1 9 8 7 ) .
of the p rotein requirements and to determ ine its optimum level in the diet for various species like P enaeus japonlcus (Kanazawa et_ al_. 1970; Deshim aru and Sh ig u e n o , 1972); monodon ( L e e , 19 7 1 ; A lava an d L im , 1 9 8 3 ) ; L i indicus (Colvin, 1 9 7 6 ; A l i . 1 9 8 2 ); P_^ merguiensis (S e d g w ic k , 1 9 7 9 ; Aquacop, 1 9 7 8 ) and P_^ azte c u s ( Venkataram iah ^ 1 9 7 5 ) . Besides these studies, evaluation of variou s plant and anim al protein sou rc e s like soyabean meal (S ic k and Andrews, 1 9 7 3 ) , mantis-shrimp (Ali et al_, 1 9 8 5 ), fish meal (Colvin, 1 9 7 6 ) and shrimp meal (Balazs al_, 1973) in the compounded diets for prawn h a s also been c a r r ie d out.
M o lluscs like s q u i d , clams, m ussles and snails h a v e been p r o v e d to be among the best diets for praw n . M olluscan meal is a major component of T aiw an e se and French p r a w n diets (M a g u ir e , 1 9 8 7 ). In Japanese p ra w n farming th e main diet consists of th e shortn^ecked clam Venerupis philipinarum (Deshimaru a n d Shigueno, 1 9 7 2 ) . In China the supplementary feed used for prawn includes fresh m olluscs such as the blue clam Corbula s p , B rachidontes s p , Anatlnella s p , V e n e ru p is vareigata, fre sh water snails and land sn a ils (Wu Qin S e , 1 9 8 7 ) .
M o lluscs like s q u id (Fennucci a n d Zein-Eldin, 1 9 7 6 ; Shigueno and Deshim aru, 1 9 7 2 ; Ali, 1 9 8 2 a ) and the m ussel Mytilus e d u lis (S ed g w ic k , 1979 Forster a n d B e a r d , 1973) h a v e been tried as protein so urc e in the p r a w n
al_. 1 9 7 6 ) .
Among molluscs, c lam s have been studied more d e e p ly than others as protein source for p r a w n and th e y are now being widely u s e d . Experim ents with short-necked clam p r o v e d that it h a s a combination of aminoacids quite similar to that of the p r a w n meat (D e s h im a r u and Shigueno, 19 7 2 ), Kanazawa (1 9 7 0 ) p r e p a r e d a purely chemical-based diet approaching the biochem ical composition o f the clam m e a t, and found the latter com paritively more effective. A cc o rd in g to N ew (1 9 7 6 ) diets w ith aminoacid profile closest to that of clam w e r e most e ffe ctiv e .
S h e w b a r f e ^ ^ ( 1 9 7 3 ) observed that clam solubles w ere good feeding attractants for Penaeus a z t e c u s . Molluscs are found to b e good source of essential aminoacids like eicosopentnoic a c id ( 2 0 ;5 w 3 ) , decosohexanoic acid (2 2 ;6 w 3 ) (Kanazaw a £t_ a l » 1977) w h ic h a r e found to influence moulting (Guary e ^ 1 9 7 6 ), A d d i t i o n of 1% lec ith in from the short-necked clam ( Tapes s p ) lipids to a se.ni-purified d i e t significantly i> 7 ip r o v e d the grow th of Penaeus japonicus (K a n a z a w a 1 9 7 9 ) . Ali (1 9 8 2 a ) evaluated the use of fr e s h meat of clam Villorita c y p r in o id e s in the d iets for Penaeus indicus an d found that it h a s got moult-inducing e ffe c t . It was also reported that powdered m eal of the marine clam Sunetta s c r ip ta gives h i g h e r growth rate in tne sam e species of p r a w n , than f i s h meal and s ilk worm pupae (A l i , 198 8 ).
( 1 ) A correct am in oacid balance, ( 2 ) Feed attraction,
( 3 ) Unknown g r o w th factor, and ( 4 ) Lipid req uirem ent.
In In d ia clams are w ide ly distributed along the east and west coast and they form sustenance fishery e sp e c ia lly in m any estuaries of M aharashtra, Goa. Karnataka and K e r a l a . Tne b l a c k clam Villorita cyprinoides (G r a y ) , selected for the p resent study, su p p o rts a regular fishery in many estuaries in Kerala, K arn a tak a and G o a providing c h e a p source of protein by way of meat. T h e annual production of black clam is about 2 9 ,0 7 7 t (Narasim ham , 1 9 9 1 ).
In this study an attempt has b e e n m ade to investigate the relative efficiency of clam meal as protein in the p r a w n diet, a n d to determine the optimum inclusion level b y studying nutritional factors l i k e food conversion ratio ( F C R ) , protein e ffic ie n c y ratio ( P E R ) , d ig e s t ib ilit y , net protein utilization ( N P U ) , biological value (BV ) and survival.
Diet foraiulation
T h e black clam Villorita c y p rin o id e s was used as aniiTial protein source for juvenile Pena b u s indicus by m aking it one of the ingredients in tne semi-purified diet. T h e feeds u s e d in the exp e rim e n t included one control feed which was a zero-clam d i e t , five experim ental feeds and a zero-protein f e e d .
T h e control feed w a s a modified form of standard purified diet recommended by Kanazawa ^ ^ (1982) . A ll the fe e d s h a d casein and gelatin as protein sources, the latter also serving as b i n d e r , while glucose, sucrose, starch and cellulose were the carbohydrate s o u r c e ; starch also served as b i n d e r . Cod l i v e r oil formed th e lipid source in the fc id s.
T h e experimental f e e d s , num bered one to five ( ^ included 5
in addition to casein and gelatin, clam as the protein s o u r c e . Clam was used in the feeds as clam meal p r e p a r e d from the meat of Villorita cyprinoides (Plate 1 ) . T h e meat extracted from the an im al was d r ie d in an oven at 6 0 °C for 15 h o u r s . The d r i e d meat was p o w d e r e d and p a s se d through a 250|i sieve. T h i s powder w a s used in v a r io u s proportions as 10%, 20%, 3 0 % . 40% and 50% in the experim ental feeds F ^ , F ^ . and
the same in all six fe e d s (Table l b , c) . Th e zero-protein f e e d (F ^ ) contained all the olher sou rc e s except protein sources.
Preparation of the feeds
Ingredients in the above proportions were in d iv id u a lly p o w d e r e d , weighed and mixed together. To this, w a t e r was ad d e d at the rate of 40m l per 100 g of feed. G elatin was s e p e rate ly dissolved at 70°C in small quantity of water. To the d ry ingredients, oil, gelatin, vitamin m ixture and m ineral mixturs w ere a d d e d and throughly m i x e d . Th e dough was steamed for 15 minutes, an d pelleted thro ugh a hand pelletiser with 1 mm diameter p o r e d die. T h e pellets were then broken into pieces of 2-3 cm length a n d d r ie d in an o v e n at 60°C for 6 hours. D r y feeds were stored in plastic containers d u rin g tne e x p e r im e n t . The proxim ate composition of these fe e d s are given in the Table 2.
Experimental design
Experim ental design followed was the com pletely ran do m ized design ( C R D ) , with three replicates for e a c h treatment.
TaDle 1 a
Composition of control feed and experimental feeds (%)
Ingredients Control feed Experim ental feeds
^2 ^3 ^4 ^'5
Casein 55 45 35 25 15 5
Clam Tieal 0 10 20 30 40 50
Glucose 4 . 5 4 .5 4 .5 4 . 5 4 .5 4 . 5
Sucrose a 8 8 8 8 8
Starcn 3 . 5 3 .5 3.5 3 .5 3 .5 3 . 5
Sodium citrate 0 . 3 0 .3 0 .3 0 . 3 0 .3 0 . 3
Sodium succinate 0 . 3 0 .3 0 .3 0 . 3 0 .3 0 . 3
Cholesterol 0 . 5 0 .5 0 .5 0 . 5 0 .5 0 . 5
Chromic o x id e 0 . 5 0 .5 0 .5 0 . 5 0 .5 0 . 5
Cod liver oil 10 10 10 10 10 10
Cellulose 1 . 7 1 .7 1 .7 1 . 7 1 .7 1 . 7
Gelatin 4 . 0 4 .0 4 .0 4 . 0 4 .0 4 .n
Mineral m ix ^ 8 . 5 8 .5 8 .5 8 . 5 8 .5 8 . 5
Vitamin m ix * * 3 . 2 3 .2 3 .2 3 . 2 3 .2 3 . 2
10C% 100% 100b 100^ 100%
* c o m p G s i t i o n a s g i v e n i n T a b l e l b .
* * c O iT ip o s it io n a s g i v e n i n T a b l e Ic .
I ^ l e lb
CotQposition of Mineral mixture
Mineral g /lO O g feed
Calcium lactate 2 .7 2 0
PotassiuTi dihydrogen orthophosphate 2 . 0 0 0
S o d ium dihydrogen orthophosphate 0 . 7 9 0
M agnesium sulphate 3 . 0 2 0
M angan ese chloride 0 . 0 0 4
F errous chloride 0 .0 1 5
Composition of Vitamin mixture Table Ic
W ate r soluble vitamins
mg/lOOg feed
A s c o r b ic acid (S o d iu m salt) 2 . 0 0
C h o lin e chloride 0 . 6 0
F o lic acid 0 . 3 0
Nicotinic acid 6 0 . 0 0
Pantothenic acid 6 0 . 0 0
Paraam ino benzoic a c id 1 0 . 0 0
P y r id o x in e h y d r o c n lo r id e 1 2 . 0 0
Riboflav in 8 . 0 0
T h ia m in e h y d r o c h lo r id e 4 . 9 0
Cyanocobalamine 0 . 0 8
Fat soluble vitamins
Biotin 0 . 4 0
^ -carotene 9 . 6 0
C alcipherol 1 . 2 0
Inositol 4 0 0 . 0 0
M enadione 4 . 0 0
•C -Tocopherol 2 0 . 0 0
raole 2
Proxioiate composition of feeds (%)
Control E x p erimental fe e d s
feed
^ 2 ^3 ^ 4 ^5
Protein 4 6 .2 0 43 .1 0 4 4 .6 0 4 4 .6 0 4 4 .6 0 4 4 .6 0
Nitrogen-free extract
2 7 .2 0 3 2 .5 0 3 1 .3 4 3 1 .5 2 3 1 .3 5 3 1 .1 7
Fat 1 2 .0 0 9 .0 0 9 .0 0 9 .0 0 9 . 0 0 9 .0 0
Moisture 8 . 0 0 8 .5 0 8 .2 0 8 .0 0 8 . 1 0 8 .2 0
A sh 6 . 5 0 6 .6 0 6 .5 0 6 .5 0 6 .5 0 6 .5 0
F ib r e 0 . 1 0 0 .3 0 0 .3 6 0 .3 8 0 .4 5 0 .5 3
Experimental facilities
C irc u la r plastic ta b s of 54 cm x 30 cm size an d 50 litre capacity were used to rear tha p r a w n during the experiment (P la t e 2 ) . Th e tabs were arrang ed on wooden r a c k s and the various treatments were random ly alloted. A ll the tanks w e r e covered w ith velon screen to prevent the prawns jam p in g out.
Experimental animals
T h e clam used for the preparation of clam meal w a s collected from Nettur, situated about 13 km southeast of Cochin H a r b o u r . They w ere brought from the field to the laboratory in plastic buckets containing w ater and stored at -8°t) in a d e e p freezer.
J u v e n ile s of the In d ia n white p r a w n Penaeus indicus (Plate 3) h av in g an average weight of 1 ± 0 .3 gram and average length of 55±2mm w ere collected from backwater can als located in the Vypeen isla n d near C o c h in . Initially the juveniles w e r e acclimatized to the experim ental conditions for 5 d a y s . During this transit phase they w e r e not f e d . After this p h a s e the p raw n s were randomly selected and introduced in to the experimental tubs at the rate of 10 p r a w n s /t u b , and w e r e fed with th e respective fe e d s to acclim atize them to the artificial f e e d s . Feeding w as suspended on the day prior to the start of th e experim ent.
Plate 3. The Indian white prawn Penaeus indicus H. Milne Edwards
At the start of the experiment the length an d weight (length measured to the nearest 1 mm fro.Ti the tip of rostnim to the tip of telson and tne w eight to the nearest 0 .0 1 g on a top loading balance) of the individual anim als were r e c o r d e d .
Water replacement
T h e plastic experim ental tubs w e r e filled with sediment-free sea water, diluted to the salinity of 15-20 p p t using fresh w a t e r . The quantity of water in the tub was maintained at the rate of 2 litres per p r a w n . One-third of the quantity of water was replaced every d a y with complete replacement once in four d a y s . The aerator stones were cleaned with fre sh water once in a week to p re v e n t algal o v e r g r o w t h .
Feeding strategy
T h e shri.Tips were fed twice d a i l y , one-third ration between 0900 and 1000 h o u rs and tne rest between 1 6 0 0 and 1700 h o u rs at the rate of 10% (d r y matter basis) of the body weight p e r day for the first week and 8% per d a y for the succeeding w eeks. C a r e was taken to see that the feeding le v e ls selected w e r e in excess to an im al's r eq uirem ent. They w ere weighed ind iv id u ally ev e ry ten days to determ ine the w e ig h t gain and feed allowance.
E v e r y morning, b e fo re feeding, feed remains an d other detritus in each tub w ere siphoned o u t . Mortality, whenever o c c u r e d , was n o te d . When the shrimps were removed for weighing, the tubs were cleaned throughly to remove the algal growth on th e inner surface.
T h e faecal matter from each experimental tub w as collected w ith a wide mouthed pippette. T h is was im m ediately rinsed w ith distilled w ater to remove traces of s a lts , and then d r i e d . The s am p le from replicates of each treatment were poo led and a n a ly s e d .
T h e left-over feed w as collected e v e r y morning on a bolting s ilk cloth by keeping it at one end of the siphoning tube w h e n the water was siphoned o u t . The collected feed was w a s h e d with d istilled water, and
>
transferred to a pre- weighed (W ) p e t r i d i s h , dried in an oven and then weighed ( W ^ ) . The w eig h t of left-over feed (W^-W) a i d s in calculating the consumption rate.
Hydrological param eters (d isso lv e d oxygen, s a lin it y , temperature, pH and am m onia) were monitored r e g u la r ly . Oxygen s u p p l y was ensured by uninterrupted aeration. T h e salinity w as maintained at 15-20 p p t as suggested b y Venkataranaiah et_ ^ (1975t^ . T h e hydrological data in respect of each exp e rim e n t are g iv e n seperately in T a b l e 3.
T h e experiment w a s carried out for 45 d a y s . At the termination of the e xp erim ent equal nu m b e r of anim als from all the treatments w ere sacrificed and kept in the d e e p freezer for carcass a n a ly s is .
Determination of metabolic faecal nitrogen (M F N )
For the determination of biological value of a protein, the true digestibility of protein is required, a n d this involves the determination of faecal nitrogen w hich contains not only the digested nitrogen from the diet bat also the nitrogen excreted due to metabolic activity in the b o d y .
Metabolic faecal nitrogen (M F N ) w as determined b y feeding the anioials w ith a known quantity of nitrogen-free d ie t , an d the nitrogen appearing in the faeces is therefore considered as the metabolic faecal nitrogen (M itchell and B e r t, 1 9 5 4 ; Forster an d Gabbott, 1 9 7 1 ) .
F o r calojlating M F N , animals w e r e individually h e l d seperately in six rearing containers an d fed with zero-protein diet or in o t h e r w a r d s, nitrogen-free diet (^ ) 'a d libitum' for 20 d ay s. F a e c e s were collected every d a y , and the nitrogen and chromic o x id e in the d ie t and faeces w ere determ ined. At the end of the experim ent the c arcasses of the anim als were an aly sed for determining the net protein utilization.
M F N excreted w h en lOOg of feed consumed = A x B C
A =5 Percentage nitrogen in faeces of animal fed w ith zero-protein diet B = Percentage ind icato r in zero-protein diet,
C = Percentage in d icator in fae c e s.
M F N due to amount of test diet consumed = E A B
D C
D = Chromic o x id e in test diet,
E = Chromic o x id e in faeces of anim als fed with test diet.
T h e value obtained is substracted from the total faecal nitrogen of the test group animals to obtain the corrected faecal nitrogen of the test group.
Digestibility
Digestibility of p rotein in the fe e d was determ ined using the inert internal m a r k e r chromic o x i d e (C r2 0 2) w h i c h has been successfully u se d to study digestibility of nutrients in p r a w n s (Forster an d Gabbott, 1 9 7 1 ; Colvin, 1 9 7 6 ; Ashmore e ^ 1985 and Sm ith e ^ a^, 1 9 8 5 ), The m ethod consists of adding known amount of chrom ic oxide ( 0 .5 % ) in the fe e d . T h e chromic o x i d e was excreted out by the anim al u n dig ested . Th e faeces w as collected for a period of time and the protein and c h r o m ic oxide in the faeces a n d diet were d e te r m in e d . T h e apparent d ig estib ility coefficient was calculated by the following formula:
A p p a r e n t digestibility coefficient -
% chromic o x i d e in the diet
% chromic o x i d e in faeces % nutrient in diet
% chromic o x i d e in the diet ^ % nutrient in faeces
Using the corrected faecal nitrogen of the test group, the true digestibility of protein w as calculated by the formula :
% corrected
% chromic oxide in diet v protein in faeces True digestibility = 100 1, chromic oxide in fai-ces ^
diet
Water stability pellets
Water stability of feed pellets was evaluated b y employing the method d e s c r ib e d by Jayaram 8 Shetty ( 1 9 9 1 ) with minor modifications. T h e loss of w eight of pellets due to leaching when k e p t under water at specified time interval w a s determ ined. For this p u r p o se cone-shaped pouches w e r e made with bolting silk (1 mm m esh ). T h e s e were thoroughly washed w it h water and d r i e d at 60®C. T h e feed pellets were cut into pieces of approximately 5 m.n length. T h e s e samples w e r e weighed at the rate of 8 sam p les for each f e e d .
T h e pouches along with pellets w e r e carefully lowered into the
;vater and p laced in p e t r id is h e s kept at the bottom of a plastic container witn water of 18 ppt s a l i n i t y . At the end of 2 h o u r s , one set of two poucnes w e r e carefully ta ke n out of w a t e r . T h e ^ w e r e gently d ip p e d in a container of fresh water for 3 minutes to remove the a d h e r in g salt. T h e y were then transferred to t h e oven and d r ie d at 60°C and w e ig h e d .
In the. same m ann er, two pouches each were ta ke n out at the end of 4 ,6 an d 8 hours and treated as mentiooned a b o v e . T h e loss in the weight of pellets was calculated by the difference in the weight b e fo re and after the immersion of p e l l e t s . Experim ent was repeated twice and average v a lu e s were taken.
Analysis
T h e levels of c r u d e protein in the feeds, faecal matter and the carcass w e r e determined b y rnicro-kjeldahi method ( A O A C , 1 9 7 5 ). C r u d e fat in the feed was estimated b y soxhlet extraction m eth o d .
A s h content in the feeds was found out by k e e p in g pre- weighed sample in muffle furnace at 60 0 °C for 6 hours and C r u d e fibre by doing acid and alkali digestion followed by kee p in g in muffle furnace at 5 0 0 ° C for 3 hours (A O A C , 1 9 7 5 ). T h e chromic o x id e in the feed and faecal matter was estimated b y the method suggested by M cGinnis and Kasting (1 9 6 4 ).
W ate r temperature w a s measured w ith an o rd inary thermometer of 0-50®C range with 0 .1 a c c u r a c y . Salinity w as estimated b y Mohr-Knudsen metfiod, and dissolved o x y g e n using the m odified W inkler m ethod, as g iv e n by Strickland and Parsons ( 1 9 6 8 ) .
T h e p H of water w a s measured using a digital p H m eter. Am m onia concentration in the water w a s determined b y phenol hypochlorite m ethod (Solarzano, 1 9 6 9 ) ,
Parameters studied
1) % growth in length/weight : Final length/w eight - Initial length/weight Initial length/weight
2) Food conversion ratio (F C R ); Average w eig n t of food consuaied(dry weight) A v e r ag e live weight gain
3) Protein efficiency ratio : Average liv e weight gain Average protein consumed
4) Gross conversion effici(ncy (K^%)
Increase in average wet w eig h t
Consumption ^
5) Net conversion efficiency
Increase in average wet w e ig h t .
Assim ilation ^
6) Nst protein utilization (NPU)
Body nitrogen of test group anim als
B od y nitrogen of animals receiving zero-protein feed Nitrogen consumed
7) True digestibility : _ % Indicator in diet % corrected prot3in
% Indicator in faeces x in faeces____________ xlO O
% protein in diet
8) Survival rate (%) Initial num ber of animals
Final n u m b e r of animals
Initial n u m b e r of animals
X 100
J) Biological Value Net protein u tiliza t io n ________
True d i g e s t i b i l i t y of protein
10) ivloulting rate was calculated using the formula given b y Petriella (1 9 9 0 )
Moulting rate
Moult percentage m
n
Moult percentage________
Mean life of the group W n ^ X 1 0 0
Number of moults
Initial nuTiber of animals
Mean life of tne group was calculated by adding the number of d a y s each individual survived and then taking th e mean.
Statistical Analysis
T h e data obtained with various parameters w e r e subjected to Analysis of Variance ( A N O V A ) to fin d out the significance betw een treatments and Mean values were com pared by least significant difference (L S D ), in both cases following Snedecor a n d Cochran ( 1 9 7 3 ) .
Table 3
Hydrographic parameters observed during the experim ait
Treatment Salinity(ppt) O x y g e n (m l /l ) pH TemperatureC ®C)
Control 1 5 .2 + 1 4 ± 0 . 3 8.06 ±0.2 28.5 + 0 .5
1 5 .0 ± 1 4 ± 0 . 2 8 .1 0 t 0 . 1 2 7 .8 + 0 .5
^2 1G.8 + 1 4 ± 0 . 3 8 .1 0 ± 0 . 1 2 7 .8 + 0 .5
^3 1 6 .0 + 1 3 .7 ± 0 . 3 8 .0 5 ± 0 . 2 2 8 .0 + 0 .5
^4 15 .8 + 1 4 ± 0 . 3 8 .2 ± 0 . 2 28.5 + 0 .5
F
5 15 .4 + 1 4 ± 0 . 2 8.05 ± 0 . 1 2 8 .0 + 0 .5
R E S U L T S
T h e results of the experi-nents conducted to evaluate the clam iieal, its co.Tiparative efficiency at different inclusion levels as feed for Penasus inJicus are given in Tables 4 to 9.
Proxiuate couposition of claiD oieal:
The result obtained in regard to proxi:nat8 an a ly s is of cla,n .neal is given in Table 4. w n ic h sh ow ed a h ig h protein (5 0 .8 2 % ) as ’.veil as lip id content ( 8 . 5 % ) in the clam meal indicating that clam meal is suitable to tne nutritional requirements of the praw n .
Increase in length, liva wsight and dry weight
In respect of six fe e d s (denoted as Control, F . F , F-, F and F )
^ ^ O ^ w
the praw ns fed on the feed F (30% clam meal) reg istered the high est 0
growth of 3 0 .2 2 % in length, 5 2 .5 0 % in liv e weight and 9 6 .1 3 % in dry w eight (Table 5) . Animals fed with F^ (40% clam tieal) ob tained the second highest g row th of , 28.34% in length, 4 4 .4 8 % In live w eig h t and 9 2 ,6 6 % in dry w e ig h t . --- --- Penaeus in d ic u s fed on F^ 5 (50% clam 'neal) showed the th ird best yrowtn rate with a grow th of 2 5 .7 7 % , 39.50% 8 3 .0 % in length, liv e weight and d r y weight r e s p e c t iv e ly . F . . . .
^ / a t' ^ 2 (2 0 % clain meal) provided a grow th
of 16.9% in lengta, 3 9 .3 3 % in live weight and 87.58% in d r y weight. Among the experim ental fee-ls, the feed with 10% clam meal bad sh o w n the
Table 4
Proxiioate composition of the clato .oeal (% )
Protein 5 0 .8 2
Fat 8 . 5 0
Nitrogen free extract 2 0 .6 3
Ash 1 0 .5 0
Moisture 9 .3 5
Fibre 0 . 2 0
Estimated growth in length, live weight a n d d r y weight of Penaeus indicus juveniles fed with different feeds
T a b le __^
Paranieters Control Experimental feeds
feed
" l ^2 ^3 ^5
Initial average length (m m )
5 5 .5 55.7 5 5 .5 5 5 .6 5 5 .4 5 5 .5
Initial average weight (m g )
1022 1023 102 2 1000 1023 1000
Initial average dry weight (Tig)
151 156 153 155 150 150
Final average length ( m i T i )
5 7 .9 61.1 6 4 .9 7 2 .4 7 1 .1 6 9 .8
Final average weight (m g )
1064 1402 142 4 1525 1478 1395
Final averRge d r v weignt (m g )
203 277 287 304 289 282
% increase in length 3 .9 0 9.60 1 6 .9 0 3 0 .2 2 28.34 2 5 .7 7
% increase in weignt 4 .1 1 37.05 3 9 .3 3 5 2 .5 0 44.48 3 9 .5 0
% increase in d r y weight
3 4 .4 4 77.56 8 7 .5 8 9 6 .1 3 92 .6 6 8 8 .0 0
Food conversion ratio 1 0 .0 9 2.11 2 . 1 0 1 .6 0 1.70 1 . 8 3
loivest growth of 9.5% in le n g tn , 37.05% in live weight and 77.56% in d ry weight. T h e lowest growth was recorded in the case of the control feed
’.vitii a g ro w tn of 3.9% in length, 4.11% in liv s weight an d 34.44% in d ry weight.
A n a ly s is of variance (ANOVA) showed that the growtn in length, l iv e weight and d r y weight d iffe r significantly between treatnents at 1% level ( P ^ 0.01 ) ( T a b l a 10, 11 and 1 2 ) . Least significant diffarsnce (LSD) S h o w e d tnat in the case of in c r ea s e in length a l l f e e d s d iffe r significantly between then a t 1% level. In t h e case o f increase in liv e weignt, th e control feed d iffe r significantly froin all other feeds at 1% level (P ^ 0 . 0 1 ) . The Feed did not s h o w any significant difference w ith feeds F ^ . and F^. Sim ilarly feeds F ^ , and F^ d id not differ s ig n i
ficantly b e t w e e n them. F e e d s F. and F were significant at 5% level
0 4
(P 0 . 0 5 ) . In tne c a s e of dry w eight control feed sh o w e d significant difference at 1% level (P ^ 0.01 ) w ith all other f e e d s . Feeds and F^ differed significantly at 5% level ( F 0 .0 5 ) , w h i l e other feeds d id not differ significantly.
Food conversion ratio (F C R )
F i g . 4 shows the food conversion ratio of all the six f e e d s . Except th e control fe e d , all other fe e d s gave good conversion ra tes.
However, F_ recorded the best FCR ( 1 . 6 ) followed by F . F _ , F _, F. with
o 4 * 5 2 1
tiie ratio values of 1 .7 0 . 1 . 8 3 , 2 .1 0 , 2 . 1 1 respectively. Th e control feed obtained a FC R of 1 0 .0 9 , thus showing that inclusion of cla.n meal h e lp s in reducing the FCR at least by 5 tim e s . Analysis of variance (T a b l e 13)
TtME ELAPSED ( D AYS )
Fig. 1
.
Increase in length of Penaeus indicus fed with feeds having clam meal at various levels. (C-eontrol; F = 1 0 % clam meal, F2-2096 clam meal; F .= 3 0 % clam meal; F^ = 4 0 % clam meal and = 50 96 cfam meal)Fig. 2. Increase in body .weight of Penaeus indicus fed with feeds having clam meal at various lev^isTlC-control;
= 1 0 % meal meal, Fg = 20% clam m eal; F„ = 30%
clam mealj F . = 4 0 % clam meal and Fj. = 5 0 % clam
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V k a IntMvase in dry weight of j^enaeus f e d with feocis hav.ng clam meal at various 'f v c I s T T c ^ n t r o ^ F - . olam meal, F„=20% clam meiil; 1-. - 30% clam mea , F = 4 0 % clam meal and - 5ira clam meal)
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Fig- 4- T h e food conversion ratio (FC R ) of different feeds fed to Penaeus indicus.
Table 1 0 . A na ly sis o f va ria nc e f o r increase i n l e n g t h .
S o u r c e d f SS MS Remarks
T r e a t m e n t s
E r r o r T o t a l
54 59
1 7 4 6 . 6 5
8 . 3 2 1 7 5 4 . 9 7
3 4 9 . 3 3
2 2 6 6 . 9 0 H i . S i g (1^5) 0 . 1 5 4 1
Mean C o m p a r i s o n s
* * S i g n i f i c a n t a t 1% le vel
* S i g n i f i c a n t a t 5% leve l
ns no t s i g n i f i c a n t
Tabl e ] 1 . A n a l y s i s o f v a r i a n c e f or i n c r e a s e in w e i g h t .
Source d£ SS MS p R e m a r k s
T r e a t m e n t s 5 1 . 4 7 3 0 . 2 9 5
6 0 . 9 0 H i . s i g
Error 54 0 . 2 6 1 0 . 0 0 5 ( 1%)
T o t a l 59 1 . 7 3 4
Mean^ C o m p a r i s o n s
** S i g n i f i c a n t at ?% l e v e l
* S i g n i f i c a n t at 5% l e v e l
ns not s i g n i f i c a n t
Table 1 2 . A na ly s is of v a r i a n c e for i n c r e a s e in d r y w ei gh t
Source
■d f ss' MS F R e m a r k s
T r e a t m e n t s 5 0 . 1081 0 . 0 2 1 6 H i . s i g
4 1 . 5 3 8 ( 1 % )
Error 54 0 . 0 2 8 5 0 . 0 0 0 5
T o t a l 59 0 . 1 3 6 6
Mean, c o m p a r i s o n s
* * s i g n i f i c a n t a t 1% l e v e l
* s i g n i f i c a n t at 5 % l e v e l ns not s i g n i f i c a n t
Table 1 3 . An a lysis o f v a r i a n c e f o r f o o d c o n c e r si o n' r ati o ( FCR
S o u r c e d f SS MS P R e m a r k s
T r e a t m e n t 5 1 6 9 . 5 0 3 3 3 . 9 0
6 7 . 8 0 H i . S i g
E r r o r 12 0 . 0 5 4 0 . 0 0 5 ( 1 % )
T o t a l 17 1 6 9 . 5 5 7
Mean c o m p a r i s o n s
* * S i g n i f i c a n t a t 1% level
* S i g n i f i c a n t a t 5% level
ns n o t s i g n i f i c a n t
showsd that treat.nents d if f e r significantly at 1% level ( P ^ 0 .0 1 ) . LSD sriowed ttiat feads and ^
1 2 show no significance betw een the.n. Feed F^
O and F^ d if f e r significantly at 5% level ( P ^ 0 . 0 5 ) . All otaer feeds differed significantly at 1\ level (P ^ 0 , 0 1 )
Survival Rate
T h e survival rates of the praw ns fed on control and experi;Tiental feeds ( F i g . 5 ) were found the comparatively low, ranging from 40% to 60% . Among all th e feeds F^ r e c o r d ed the m axim um survival rate (60%) followed by F_ (5 5 % ) . Feeds F . and F. had a survival rate of 5 0 % , control feed
5 4 1
45%, w h ile F^ recorded the lowest su r v iv a l rate of 4 0 % . Th e process of mouUing w a s observed to be one of the major factors contributing to the mortality of sh r im p s . T h o s e which were soft,' probably just moulted w ith in 24 hours, accounted for 36% of the total m ortality.
Gross conversion efficiency ( K % ) and Net conversion efficiency(K.%)
1 ' o
T a b l e 6 shows the v a lu e s of an d K % obtained w ith all six f e e d s . X . ■ *
Feed F - s h o w e d the highest value of K . as well as K _ of 0 .6 0 and 0 .7 1
0 1 2
respectively, F^ showed th e second best and v a l u e s ( 0 .5 8 and 0 .6 9 resp ectively ). Though F s h o w e d the n e x t higher K v a lu e (0 .5 2 ) its K value was found to be lo w e r than that of F _ . The other feeds F _ , F and
D b X
control o b ta in e d value of 0 .5 1 , 0 . 4 8 and 0 .4 0 resp ectively , th e ir respective K values being 0 . 5 7 , 0 .5 1 and 0 . 4 1 .
A na lysis of variance (A N O V A ) (j a b l e 1 4 ,1 5 ^ showed that in the case of the treatments d iffe r significantly at 5% level ( P ^ 0 .0 5 ) , w h ite
treatments did not s h o w any significant difference between them
Moulting rato
It \vas found that the moulting rate values increased as the percentage of cla.Ti <-neal in the feed increased upto a certain level and after that it started d ecreasing (Taole 7 ) . The moulting rate was the maximum with (3 .7 2 ) follo w ed by F ^ ( 2 . 8 4 ) , F ^ { 2 .5 0 ), F2(2.0 0), F ^ ( 1 . 7 9 ) and control ( 1 . 6 7 ) . The moulting rate increases up to 3 0 % , with h ig h e r percentages the value reduces gradually. Analysis of v a ria n c e of the data showed that treatments differ significantly at 1%. level (P 0 . 0 1 ) (T ab le 16 i
Protein efficiency ratio (P E R )
T ne best value of P E R was sh o w n b y followed b y F^
( 0 .6 1 ) , Fg ( 0 . 5 5 ) , F^ ( 0 . 4 9 ) and F^ [ q .4 8 ) (F i g . 6) . T h e control feed showed the low est value ( 0 . 1 0 ) Analysis of variance s h o w e d that treatments differ significantly at 1^ le v e l (P < 0 .0 1 ) ( T a b l e 17 ) .
t i m e e l a p s e d ( D A Y S
Fig. 5. Relationship of clam meal levels with Survival.
(C-control; F = 10% clam m eal, 20% clam meal; F„= 3 0 % clam meal; F ^ = 40'% clam m eal and Fj= 5 0 % clam meal).
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PERCENTAGE OF CLAM IN F E E D
F i g , 6 , Relationship o f c l a m m eal levels w it h dietary i n c r e a s e in body w e ig h t a n d with p ro te in e ffic ie n c y ratio ( P E R )
T a b l e 6
Gross conv ersion efficiency ( K %) and Net Conversion e ffic ie n c y v alues
obtained fo r control and experi-nental fe e d s
F e e d s K2%
Control 0 . 4 0 0 . 4 1
0 . 4 8 0 . 5 1
^ 2 0 . 5 2 0 . 5 6
^3 0.6q 0 . 7 1
^ 4 0 . 5 8 0 . 6 9
^ 5 0 . 5 1 0 . 5 7
Table 7
Moulting rates obtained when fed with control and experitn^tal feeds
Fe e d s Moulting rate
Control 1.67
1.79
2. 00
3.72 2.84
*^5 2.50
T a b l e 1 4 . A n a l y s i s o f v a r i a n c e f o r G r o s s c o n v e r s i o n e f f i c i e n c y ( K ^ % ) .
So u r c e d f S S MS F R e m a r k s
T r e a t m e n t s 5 0 . 1 8 9 9 0 . 0 3 7 9 8
S . 9 5 b S i g . { 5 %) E r r o r 12 0 . 1 1 5 7 0 . 0 0 9 6
T o t a l 17 0 . 3 0 5 6
T a b l e 15 . A n a l y s i s o f v a r i a n c e f o r N e t c o n v e r s i o n e f f i c i e n c y ^ ^2% )
S o u r c e d f S S MS F R e m a r k s
T r e a t m e n t s 5 1 . 9 6 4 4 0 . 3 0 2 9
2 . 6 6 7 3 Not s i g n i
E r r o r 12 1 . 7 6 7 8 0 . 1 4 7 3 f i c a n t
T o t a l 17 3 . 7 3 2 2
T a b l e 1 6 . A n a l y s i s o f v a r i a n c e f o r m o u l t i n g r a t e .
S o u r c e d f SS MS F R e m ark s
T r e a t m e n t s 5 9 . 1 5 1 . 5 5 1 9
1 4 3 . 7 0 H i . S i g .
E r r o r 12 0 . 1 3 0 . 0 1 0 8 (1%)
T o t a l 17 9 . 2 8
Mean, c o m p a r i s o n s
F F F
F F
** S i g n i f i c a n t a t 1% l evel
* S i g n i f i c a n t a t 5% level
ns n o t s i g n i f i c a n t
Table 17
A n a l y s i s o f v a r i a nce f o r Protein e f f i c i e n c y r a t i o (PER)
S o u r c e df SS MS F R e m a r k s
T r e a t m e n t s 5 0 . 5 7 1 2 0 . 1 1 4 2
2 8 . 5 5 H i . S i g
E r r o r 12 0 . 0 5 0 7 0 . 0 0 4 ( 1%)
T o t a l 17 0 . 6 2 1 9
Mean, c o m p a r i s o n s
* * S i g n i f i c a n t a t 1% l evel
* S i g n i f i c a n t a t 5% l evel
ns n o t s i g n i f i c a n t
Mstabolic faecal nitrogen ( M F N )
T a b l e 8 shows the MFN v alues obtained w ith six different experim ents. In tne feeding experiments carried out, th ere was a loss in average b o d y weight of anifnals fed with zero-protein feed ( • The aniinals gradually uecam e less a c t iv e and mortality occurred. T h e MFN values showed w i d e variation ranging fro-n 287 mg N /l O O g feed to 369.50 mg N /l O O g feed, g iv in g an average value of 3 4 4 .2 0 mg N/lOO g f e e d .
True Digestibility (TD)
T h e true digestibility value of control feed w a s found to be the best as it recovered the highest value of 96.52!^ ( T a b l e 9 ) . Among the experimental feeds F^ s h o w e d the best T D value ( 9 4 .1 2 % ) followed b y F ^ , F _, F^ and F . with values 9 0 . 8 7 . 4 2 % , 86.22% and 8 4 .7 1 % re sp e c tiv e ly .
0 5 4
It w a s seen that as the clam percentage in the feed goes u p , the TD generally comes d o w n , h o w ever, th e re was one e x c e p tio n , the T D of F^ (8 6 .2 2 % ) w as found to b e greater than that of F^ ( 8 4 . 7 1 % ) .
A n o v a (Table 1 8) sh o w e d that the treatments d iffe r significantly at level ( P ^ 0 . 0 1 ) , Least significant difference sh ow ed that feeds F^ and d id not differ significantly, w h ile all the rest showed significant difference betw een them at 1% level.
Table 8
Estimated value of niGtabolic faecal nitrogen (MFN) in juvenile Penaeus indicus using the zero protein d ie t.
( T h e value is e x p r e s s e d as railligrain of nitrogen p e r lOOg of diet consumed]
E x p e rim e n t No. M F N
1 3 6 6 .1 3
2 2 8 7 .0 0
3 3 6 9 .5 0
4 3 2 5 .2 0
5 3 6 2 .3 7
6 3 5 5 .0 0
Average 3 4 4 .2 0
Net protein utilization (N P U )
T n e N P U values e x h i b it e d no correlation with the increasing amount of clan meal in the diet (T ab le 9 ) . It is important to note that all experiments h a d shown a N P U value greater than that of control d i e t . Aoiong all f e e d s , F. s h o w e d the maximum value ( 6 8 . 4 4 ) followed b y F_
4 5
( 5 7 .9 8 ) , ( 5 6 . 0 ) , F^ ( 3 9 . 4 7 ) and F^ ( 3 7 . 5 0 ) . F^ show ed a s u d d e n increase in value when c o m pa re d to F an d F feeds. A nalysis of v a rian ce (ANOVA) ( T a b l e 19) s h o w e d that all treatments differ significantly at lev3l (P < 0 . 0 1 ) .
Biological v a l u e (8V)
Biological values of the feeds g iv e n to the p r a w n is shown in the Taole 9 . M a x in u m BV w a s shown by the feed F. ( 8 0 . 7 9 ) , followed b y F_
4 0
( 6 8 .4 4 ) , F ^ ( 6 4 . 4 1 ) , F^ ( 4 1 . 5 3 ) , F ( 4 1 . 3 4 ) and control ( 3 1 ^ 9 ) . A s in the case of N P U here also all experimental feeds s h o w e d a higher value than the control. A n a ly sis of variance (T ab le 20) sh o w e d significant difference betw een treatments at 1% le v e l. LSD snow ed that feeds F^ and F differ significantly at 5% level (P ^ 0 . 0 5 ) , all the rest at 1% level (P C 0 .0 1 ) .
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CLAM PERCENTAGE IN F E E D
Fig. 7 . Relationship of clam meal levels with net protein utilization (N PU )
CLAM PERCENTAGE IN FEED
F i g . 8 . Relationship o f c la m m eal levels w ith True digestibility ( T U )
CLAM P E R C E N T A G E IN F E E D
I^ig. 9 .
Re la t i o n s h i p o f
clam m eal levelswith
Biological Valu e (HV;T a b l e 1 8 . A n a l y s i s o f v a r i a n c e f o r ‘ D i g e s t i b i l i t y .
S o u r c e d f SS M S F R e m a r k s
T r e a t m e n t s 5 3 2 6 . 7 4 6 5 . 3 4 8
1 4 2 3 . 0 8 H i . S i g .
E r r o r 12 5 . 5 1 0 . 4 5 9 2 (1%)
T o t a l 17 3 3 2 . 2 5
M ean_______C o m p a r i s o n s
** S i g n i f i c a n t a t 1% level
* S i g n i f i c a n t a t 5% level
ns n o t s i g n i f i c a n t
T a b le 1 9 .
A n a l y s i s o f v a r i a nce f o r net p r o t e i n u t i l i z a t i o n (NPU).
S o u r c e d f S S MS F R e m a r k s
T r e a t m e n t s 5 3 2 5 2 . 2 5 6 5 0 . 4 5
2 3 2 9 . 7 0 H i . s i g (1%)
E r r o r 12 3 . 3 5 0 . 2 7 9 2
T o t a l 17 3 2 5 5 . 7 0
M e a n C o m a p r i s o n s F F
F F
* * S i g n i f i c a n t a t 1% level
* S i g n i f i c a n t a t 5% l evel
ns not s i g n i f i c a n t
T a b l e 2 0 . A n a l y s i s o f v a r i a n c e f o r b i o l o g i c a l v a l u e { B V ) .
S o u r c e d f SS MS F R e m a r k s
T r e a t m e n t s
E r r o r
5
12
5 5 7 4 . 1 2
1 . 9 7
1 1 1 4 .
0 . 82
1 642
6 7 8 9 . 4 0 H i . S i g . (1%)
T o t a l 17 5 5 7 6 . 0 9
M ean C o m p a r i s o n s
* * S i g n i f i c a n t a t 1% level
* S i g n i f i c a n t a t 5% level
ns n o t s i g n i f i c a n t
Water s ta b ilit y of the feed
F i g . 10 ( a . b . c . d ) show s that the pellet stability was in v e rs e ly related to the dietary le v e l of claai m e a l . The percentage of dry inatter rernainlng d e creased witn increasing claiin meal level in the fe e d s.
A fte r an exposure of 8 hours th e feed remains w ere 77.5% of the feed before leaching for control, 75% for
well as F ^ and 72.5% for F^ ^ c a se of all fe e d s the l eaching rate was found to be higher in thhe initial stages (upto 4 h o u rs), and then slowly coming dow n.
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2 HOURS OF EXPOSURE
Fig. 10a. Relationship of clam meal levels with dry matter remaining after 2 hours exposure of feed.
(C-contro2; F = 1 0 % clam m eal, F „ = 20% clam m eal; F^= 3 0 % clam meal; F ^ = 4 0 % clam m eal and F^= 5 0 % clam meal).
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EXPOSURE
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Fig. 10b. Relationship of clam meal levels with dry matter remaining after 4 hours exposure ot feed.
(C-control; 1 0% clam meal, p2= 20% clam meal; F ,= 3 0 % clam meal; F ^ = 4 0 % clam meal and F-= 5 0 % clam meal).
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6 HOURS OF EXPOSURE
Fig. 10c. Relationship of clam meal levels with dry matter remaining after 6 hours exposure of feed.
(C-control; F-= 1 0 % clam m eal, F = 20% clam meal; F„= 3 0 % clam meal; F ^ = 4 0 ^ clam meal and Fc= 5 0 % clam meal).
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8 HOURS OF EXPOSURE
Fig. lOd. Relationship of clam meal levels with dry matter remaining after 8 hours exposure of feed.
(C-control; F ^ = 1 0 % clam m eal, 20% clam meal; F ^ . 3 0% elam meal; F ^ _ 405^ n,eal
and ?£■= 5 0 % meal).
0
D I S C U S S I O N
W hat follows is a short discussion emanating from a careful perus^dal of the foregoing results.
T h e results obtained fro:n the proxim ate an aly sis of clam meal in the present study are com parable to the values obtained b y Ali (1 9 8 8 ) for Sunetta sc rip ta :iieal (p r o t e in 48.10% , l i p id 13.55% , nitrogen-free extract 11.69% an d ash 7.62%) and b y Gopal ( 1 9 8 6 ) for M eretrix casta meal (p ro tein 56 .6 % , l i p id 8 .2 % , nitrogen-free extract 2 0 .8 % and ash 1 0 . 5 0 % ) .
A li (1982 a) rep orted an average growth rate of 1 3 .2 0 m g /d a y in Penaeus ind ic u s 'of 0 .1 g s iz e when fed w ith 33.3% protein feed having 38%
Villorita cyprinoides meat powder protein source and a growth rate of 10 m g /d a y for the same species with a stocking size of 0 . 2 g using fresii Sunetta sc r ip ta meat as f e e d .
A li (1988) recorded an increase o f 514%, 3 7 4 .2 % an d 375.8% in terms of length, liv e weight a n d d r y weight respectively in Penaeus indicus of average initial length of lO-^Oinn fed with 51% Sunetta s c r ip ta meal in 30 d a y s , Gopal ( 1 9 8 6 ) reported 575% gain in live w eight in Penaeus indicus ju ven iles of 20±5 mm fed with d ie t containing 5 1 .2 % Meretrix casta meal. Fenucci et al ( 1 9 7 6 ) observed 5 9 0 .2 4 % increase in live w eight in 42 d a y s with Penaeus a z t e c u s .
Sedg^vick (1979) stud ied the g r o w th of Penaeus oiergulensis using 69% of freeze- dried m ussel Mytllus e d u lls in diet in w h ic h the protein content w a s 3 9 .5 % and r e p o r t e d a weight gain of 5 7.1 4 % in 8 w eeks, C olvin (1975) o b s e r v e d a grow th rate of 44 m g /d a y in m er^uiensis of 0 . 9 5 g when fed w ith a cOTibined meal of fr e s h mussel and fr e s h juvenile p raw n in equal r a t io .
T h o u g h the h ig h e st growth inc rea se recorded in the present study was only 5 2 .5 5 % , is co-nparable to the result obtained b y Sedgwick ( 1 9 7 9 ) . The h i g h e r growth rate obtained by C o M n (1976) m ay be due to the co.Tibination of two protein sources ( w i t h a.nino acid composition sim ilar to p raw n ) since a mixture of two or m ore protein s o u r c e s , invariably show better g r o w th than single source (D e s h im a r u and S h ig u e n o , 1 9 7 2 ). Th e following reasons can b e attributed to the low growth rate: variation in size of p r a w n s , form of protein used a n d the protein content of the f e e d . Another reason that can also be attributed to lower g ro w th rate obtained in the present study is that certain essential am inoacids are lost during drying b e ca u se of the reactions with reducing sugars and carbonyl com pounds present in the diet a5 suggested by Swam inathan (1967) .
All (1988) has re p o r te d a Food conversion ratio (F C R ) of 1 .8 3 using a (list contaiaing 51% Suaetta scripta m eal in Penaeus in d ic u s of 10-20 mm length. G op al (1986) o b tain ed a value of 0 .92 with Penaeus indicus of 20±5 mm using 51.2% M e r e t r ix casta meal and Ali (1 9 8 2 b ) a value of 1 . 4 6
juveniles. T ne hignest F C R (1 .6 ) obtained in t h e present stud y is coinparable to tnese v a l u e s , taking into account the variation in s iz e , experimental duration and protein source. Trie water sta b ility of the pyllets are also s a i d to influence the FCR value (R a n i , 198 4 ).
Protein efficiency ratio (P E R ) o f 1 .7 7 was obtained with a diet containing Sunetta s c r ip t a Tieal in P e n a e u s indicus w it h 10-20 ti-ti lengtn ( M i , 1 9 8 8 ) . Alava and L im (1983) using 40% protein d iet with casein, fish
iTieal, s h r i m p oieal and s q u i d nieal as components r e p o r te d a PER of 0 .3 4 in Penaeus monodon ju v e n il e s . The h ig h e s t PER of 0 . 6 2 obtained in the present s t u d y was for the group having 30^ incorporation of clam meal in tile d ie t , w h ich show that clam protein is most efficiently utilized by
the p r a w n s at this level of inclusion.
A li (1982 b) rep orted a su r v iv a l of 70% in 30 days with 38%
Villorita cyprinoides meal diet in P enaeus indicus juveniles (1 0 0 mg ) . Gopal (1 9 8 6 ) using a d iet with 50% clam meal ( M eretrix casta) obtained a survival rate of 64% in 30 d a y s , Ali (1 9 8 2 b) using fr e s h Sunetta scripta as feed obtained 30% s u r v iv a l in 30 d a y s , in Penaeus indicus of 100 mg initial w e ig h t , Villegas (1978) found that the g r o w th and su r v iv a l of Penaeus .nonodon larvae fe d with Tapes clam was only next to com pounded diets. A ll the afore mentioned studies agree with th e present s t u d y in that the survival was found to be generally low w h e n fed with clam included d i e t s , Gopal ( 1 9 8 6 ) reported 1 1 post moult d e a t h s out of 27 moults observe'! during tne 40 d a y s of exp e rim e n t. This is entirely in agreement witii the present study w h e r e around 36% post moult d e a th s were o b s e r v e d .
T h e higher moult percentage v a lu e s obtained w it h F , F an d F
1 2 3
when c o m p a re d to the control feed may b e due to the moult inducing factor reported in fresh Sunetta scripta by A l i (1982 a ) . T h e same h a d found that the h ig h moulting rate resulted in high m ortality . Gopal (1 9 8 6 ) reported that prawns fed on clam meal ( Meretrix c a s t a ) h ad significantly lower calcium and p h osp o ro us levels coinpared to those fed on diet with fisn m ea l, crab meal an d shrimp m e a l. This may indicate that low er calcium and phosphorous metabolism m ay perhaps affect these p ra w n s resulting in comparitively h i g h mortality rates, especially during post-moult stages ( N e w , 1 9 7 6 ).
Metabolic faecal nitrogen (M F N ) in Penaeus in d ic u s was determ ined for the first time by A li (1 9 8 8 ) and rep orted a value ranging from 2 4 8 .5 mg to 3 5 1 .6 -ng N/lOO g diet (average 3 2 6 .4 mg N /l O O g d ie t ). losing zero-protoin diet, Nose ( 1 9 6 7 ) determined M FN in young rainbow trout and obtained varying values of 8 5 ,7 , 1 3 9 .7 and 151.0 mg N /lO O g diet in 3 different experim ents. Forster and Gabbott (1971) determined M F N in Palaemon serratus and o b tain ed a value of 1 8 5 .2 ± 2 7 .9 m g /1 0 0 g diet.
T h e value obtained in the present study are c o m parab le to the value obtained b y Ali (1 9 8 8 ). H e r e also v a r y in g values w e r e obtained w ith 6 different experim ents. T h e significantly different v a lu e with Palaem on serratus m ay be due to th e difference in the nature a n d quantity of faecal me.nbrance in the two t y p e s of praw n s. In tha case of finfish, th e low value o b tain ed when c o m p a r e d to p raw n is because p r a w n s are kn o w n to secrete a chitinous p e r itro p h ic membrane around the faecal pellets (F o r s t e r . 1953) .
