TOTAL SULFUR AMINO-ACID REQUIREMENT OF JUVENILE HYBRID STRIPED BASS (MORONE-CHRYSOPSXM-SAXATILIS)

Two separate feeding trials were conducted to determine the total sulfur amino acid requirement of hybrid striped bass. Semipurified diets containing 35% crude protein from fish muscle and crystal-line amino acids were supplemented with graded levels of methionine. Each diet was fed to juvenile fish in triplicate aquaria receiving freshwater for 8 weeks. Fish fed the basal diet which contained 0.38% methionine and 0.13% cystine experienced complete mortality within 1 week. Prior to death, some fish fed inadequate methionine were observed to have bilateral cataracts. Weight gain and feed efficiency of fish were significantly (P < 0.01) affected by supplemental methionine. Regression analysis of weight gain data using the broken-line model indicated a total sulfur amino acid requirement (+/- s.e.) of 1.0% (+/- 0.02%) of dry diet or 2.9% of dietary protein.