Effects of available lysine concentrations in 28 and 32% protein diets on growth, feed efficiency, processing yield, and fillet composition of pond‐raised channel catfish, Ictalurus punctatus

A study was conducted in earthen ponds to investigate the effects of available lysine (AL) concentrations in 28 and 32% protein diets on production and processing characteristics, proximate composition, and lysine concentrations in the fillet of channel catfish, Ictalurus punctatus. Diets were formulated to contain 28% protein with 1.22 and 1.43% AL, and 32% protein with 1.43 and 1.63% AL, which were equivalent to 4.37, 5.1, 4.46, and 5.1% AL of protein, respectively. Fingerlings with a mean initial weight of 32 g/fish were stocked into 20 ponds (0.04 ha) at 19,760 fish/ha. Fish were fed once daily to apparent satiation for 181 days. No significant differences were observed for total diet fed, net yield, weight gain, survival, or fillet proximate composition among dietary treatments. However, the 28% protein with low AL diet (1.22% AL of diet or 4.37% AL of protein) resulted in significantly lower carcass and fillet yield and fillet lysine level compared with fish fed the 28% protein diet with 1.43% AL (5.1% AL of protein) and 32% protein diets with 1.43 and 1.63% AL (4.47 and 5.1% AL of protein). Results suggest 1.43% AL of diet is adequate for both 28 and 32% protein diets for optimum growth, processing yield, and lysine retention in fillets for pond‐raised channel catfish.