INFLUENCE OF PRACTICAL D IET SUPPLEMENTATIONW ITH FREE D-METHIONINE ON THE GROWTH AND BODY COMPOSITION IN TILAPIA OREOCHROM IS N ILO TICUS 譕. AUREUS

Tilap ia is the most commercially cultured species in the South China, and the culture scale has rapidly developed in the past few years. Due to high cost and limited availability, the rep lacement of fish meal by plant protein sourcesis of great interest. It is very important aspects that how to imp rove the utilization of p lant p rotein sources in aquafeeds.Therefore, the aim of the p resent studywas to investigate the effects of dietary supp lementation with methionine on growth,body composition and levels of serum amino acids in juvenile hybrid tilap ia. The tilap ia O reochrom is niloticus 譕. aureus(mean weight of (4.18?.04) g) were fed separately in 15 fiberglass tanks (400L) with 30 fish per tank. Five isonitrogenous and isoenergetic diets (crude protein 3%, gross energy 15. 8 kJ /g) were formulated, in which free aminoacids were supp lemented by free Dmethionine at 0. 00%, 0. 05%, 0. 10%, 0. 15% and 0. 0%, respectively. Everyexperimental diet was taken three repeats, and fed p ractical diets containing methionine 0. 45%, 0. 50%, 0. 55%,0160% and 0. 65% ( containing cystine 0.5% ) thrice a day for 60 days at 4% -8% of body weight respectively. Results indicated that the p ractical diets containing free methionine imp roved the specific growth rate ( SGR), feed conversion ratio (FCR), apparent p rotein retention (APR) and hepatopancreas lip id content in comparison with the basal diet(p0.05). Viscera ratio and hepatosomatic index decreased significantly with increasingmethionine supp lementation level (p>0.05). The results suggested thatmethionine supp lementation can significantly imp roved growth performance in juvenile hybrid tilap ia. Free methionine was p roved to be a significantly betterway of dietaryp rotein supp lementation.