Dietary protein and essential amino acid requirements of the juvenile Black Tiger prawn Penaeus monodon

Abstract

The quality and quantity of the dietary nutrients, particularly protein and energy, affect theneconomic optimum growth of prawns. Previous studies indicate that the dietary proteinnrequirement of the black tiger prawn (Penaeus monodon) is high, between 35 and 50%.nTwo of the factors for the variation in the dietary protein requirement are the availability ofnenergy and the content of essential amino acids in the diet. These factors have not beennaddressed in detail for the black tiger prawn. This study tries to clarify some of the issuesnrelated to protein and amino acid requirements of the black tiger prawn.In Chapter 2, maintenance requirements and the efficiency of protein and energynutilisation by prawns were examined. Fifty-six prawns (28 male and 28 female) from twonsize groups (mean weight 2.99 g and 23.38 g) were individually placed in 20 litre tanks.nAnimals were fed with a commercial prawn feed containing 42% protein and 19.24 Mj/kgnenergy. Each size group were fed at seven different feeding levels, which were set atnequal increments from 0 to ad libitum (inclusive), for a period of 28 days. The ad libitumnintake levels were 7% for small prawns and 2% for large prawns. Results indicated thatnmaintenance requirements for digestible energy and protein were 310 JDE/gW/d andn0.008g DCP/gW/d, respectively. There was no significant difference between thenmaintenance requirements of either size or sex. The utilisation efficiency for energy andncrude protein was significantly different between the two sizes, but not so between thensexes of the prawns. Efficiency of use of absorbed energy by small and large prawns wasn0.34 and 0.59, respectively, while efficiency of utilisation of protein by small and largenprawns was 0.52 and 0.77, respectively.In Chapter 3, the use of carbohydrates as an energy source and their protein-sparing rolenin the diets of juvenile prawns were investigated. Ten juvenile prawns (mean weight 2.84ng) were reared for six weeks in 250 litre tanks with flow-through seawater system.nExperimental diets had squid meal and wheat starch as protein and carbohydrate sources,nrespectively. The protein content of the diets was reduced from 38.3% to 14.8% bynreducing the squid meal component of the diet. The gap was filled with starch. Therenwere 11 diets and each diet had 3 replications. The results showed that a 10% inclusionnof starch reduced the need for protein by 13.5% (from 38.3% to 33.1%) without a significant reduction in growth. This indicates that some of the protein in the diet is usednas an energy source rather than utilised for protein deposition.In Chapter 4, possible sources of amino acids for prawns in the experimental environmentnwere studied. Two main amino acid sources investigated were the exuvia of the prawnsnand seawater. Exuvia of the 46 prawns were collected immediately after moulting andnexuvia and moulted prawns were analysed for proximate and amino acid compositions.nThe relationship between the weight of exuvia and the whole prawn body was established.nProtein and amino acid analyses indicated that unless collected after moulting, prawnsncould ingest significant amount of these nutrients by eating their moult. Analysis ofnseawater filtered through a 10 }im filter did not show the presence of any amino acids,nindicating that seawater would not provide any amino acids to prawns during feeding trials.In Chapter 5, changes in composition of free amino acids in the hemolymph of prawnsnwere examined to find out whether this could be used to estimate essential amino acidnrequirements. One hundred and four prawns (average body weight 12.14 g) were placednin individual experimental cells. All the prawns were fed at 0 hour with a commercial diet.nHalf of the prawns were fed at the 10th hour while the other half were starved. Twonprawns from the fed and starved groups were randomly taken from the experimental cellsnand hemolymph was collected. This was done starting at 0 hour and continued every twonhours until the 12th hour. Hemolymph was analysed for its free amino acids composition.nResults showed that the concentration of some non-essential amino acids (glycine,nglutamine, serine, citrulline and asparagine) and essential amino acids (isoleucine,nleucine, threonine, valine and lysine) significantly changed with time. However there wasnno significant difference between the concentration of free amino acids in fed and starvednprawns except the concentration of phenylalanine. It was concluded that short periods ofnstarvation were not appropriate for estimating essential amino acid requirements ofnprawns.n n n n n n n n n n n n n n n