PERFORMANCE OF SUNSHINE BASS FED SOYBEAN-MEAL-BASED DIETS SUPPLEMENTED WITH DIFFERENT METHIONINE COMPOUNDS

Practical diets that contain high levels of plant proteins often requi re supplementation with methionine to satisfy the total sulfur amino a cid requirements of animals. The present study was designed to evaluat e L-methionine, DL-methionine, N-acetyl-DL-methionine (acetylmethionin e), and or-methionine hydroxy analog (MHA) as supplements in soybean m eal-based diets for sunshine bass, the hybrid of white bass Morone chr ysops female x striped bass M. saxatilis male. Five practical diets we re formulated to contain crude protein at 40% of dry weight, with 75% of the protein provided by soybean meal and 25% provided by menhaden f ish meal. The basal diet provided total sulfur amino acids from intact protein at approximately 1.0% of dry diet, and the test diets were su pplemented with each of the methionine compounds at 0.3% dry weight on an equal-sulfur basis (except for an additional 25% for MHA). A contr ol diet was formulated to contain 40% crude protein exclusively from m enhaden fish meal. All experimental diets were compared with a commerc ial diet containing 45% crude protein. Triplicate groups of juvenile s unshine bass (initial weights, 8-9 g/fish) were fed each diet in a bra ckish-water (5%) recirculating system for 8 weeks. Fish fed the soybea n-meal-based diets supplemented with L-methionine, Dr-methionine, and acetylmethionine had weight gains and feed efficiencies similar to fis h fed the commercial and control diets. However, MHA was not efficient ly utilized by sunshine bass, and performance of fish fed that diet wa s significantly (P < 0.05) reduced, as was that of fish fed the basal diet. The highest protein efficiency ratio values were observed for fi sh fed the control diet and the diets supplemented with L-methionine a nd DL-methionine. Whole-body protein and moisture were not affected by the dietary treatments; however, differences in whole-body lipid and ash were observed among some treatments.