REPLACEMENT OF FISH MEAL BY dehulled soybean meal WITH METHIONINE AND lysine SUPPLEMENTATION TO DIET FOR Juvenile Sterlet Sturgeon, Acipenser ruthenus
Soybean meal is considered to be one of the most suitable and stable supplies of an alternative ingredient for replacing fish meal to reduce the cost in commercial fish feed industries. This study was designed to investigate the effects of the replacement of fish meal by dehulled soybean meal (DSBM) with dietary methionine and lysine supplementation on meat quality for sterlet sturgeon. The DSBM of 25, 50, 75 and 100% was added to the basal diet (DSBM0) containing 42% protein and 11% lipid designated to DSBM25, DSBM50, DSBM75 and DSBM100.
Five groups (three replicates/ group) of 300 fish (60 fish per group) of a mean body weight of 125.4 g selected from 1,000 fish were randomly allotted to each of 15 tanks (2 × 1 × 0.4 m). Water temperature and dissolved oxygen levels were kept at 20±1℃ and over 6 mg O2 L-1, respectively. Fish were fed the diets by hand at the rate of 3 to 4% of fish body weight per day at 08:00 h, 13:00 h and 18:00 h, for 10 wk.
Total amino acid contents of whole body (DSBM0, 14.8%; DSBM25, 14.1%; DSBM50, 14.7%; DSBM75, 15.0% DSBM100, 13.4%; % as-is basis) of fish groups were not significantly difference (p>0.05). Also, total free amino acid contents of whole body (DSBM0, 0.155, mg/100mg; DSBM25, 0.171 mg/100mg; DSBM50, 0.146 mg/100mg; DSBM75, 0.160 mg/100mg and DSBM100, 0.143 mg/100mg; as-is basis) of fish groups were not significantly difference (p>0.05). Aspartic acid and L-proline were, however, greatly different (p<0.05) among fish groups fed five experimental diets. In whole body fatty acid composition, saturated fatty acids [SFA, (DSBM0, 34.60%; DSBM25, 32.53%; DSBM50, 34.00%; DSBM75, 34.34%; DSBM100, 34.09; % of total fatty acids)], monounsaturated fatty acids [MUFA, (DSBM0, 41.65%; DSBM25, 39.65%; DSBM50, 42.00%; DSBM75, 40.72%; DSBM100, 39.45; % of total fatty acids)] and polyunsaturated fatty acids [PUFA, (DSBM0, 23.71%; DSBM25, 27.83% DSBM50, 24.01%; DSBM75, 25.93%; DSBM100, 26.46; % of total fatty acids)] were not significantly different in fish group (p>0.05).
From the present study, it was concluded that replacement of fish meal by DSBM with dietary methionine and lysine supplementation may not affect amino acid, free amino acid and fatty acid profiles in whole body of sterlet sturgeon. However, no comparisons with other studies could be made because investigations on the use of soybean meal in relation to meat quality of sterlet sturgeon have not yet been reported.