Digestibility studies on fisheries by-product based diets for Penaeus monodon

Abstract

Apparent dry matter digestibility (ADMD) and apparent protein digestibility (APD) of four isonitrogenous practical diets (40% crude protein) containing different combinations of marine animal protein sources prepared from fisheries by-products were determined for juvenile Penaeus monodon (average weight 4.65 ± 0.99 g). An indirect method using chromic oxide (Cr 2O 3) as an indicator was employed for the determination of digestibility. The diet formulations tested contained mollusc and crustacean waste meals (scallop and shrimp head, diet D1) and fish and crustacean waste meals (sardine and lobster, diet D2; sardine and shrimp head, diet D3). Diet D4 contained commercially available fish and crustacean meals (anchovy and shrimp). In addition, all diets contained soya-bean meal, wheat flour and rice pollard as plant protein sources except for diet D3 in which the diverse plant protein sources were replaced by lupinseed meal. The ADMD and APD values of the three diets D1, D2 and D4 were similar with a range of 75.8–78.1% and 92.0–92.8%, respectively. The diet combining sardine and shrimp head meals with lupinseed meal (D3) had significantly lower ADMD and APD values of 53.2% and 85.4%, respectively, than the other three diets. When the essential amino acid index (EAAI) was used to evaluate the protein quality of these diets with whole juvenile P. monodon as the reference protein, all diets gave a similar result with a range of 0.94–0.96. The results indicate that fish meals prepared from fisheries by-products were digested as efficiently as those prepared from commercial fish meals and have potential as alternative animal protein sources in shrimp diets. However, replacement of the plant protein sources with lupinseed meal lead to a decrease in the digestibility with P. monodon.