Protein and energy requirements of fingerling channel catfish for maintenance and maximum growth

In two separate experiments, purified diets containing 25% crude protein and 2.85 kcal/g and 35% crude protein and 3.99 kcal/g were fed at incremental rates [0-5% of body weight (BW)/d] to fingerling channel catfish (Ictalurus punctatus) in aquaria for 8 wk. Linear (r2 = 0.95) increases in growth rate were observed in each experiment with increases in feeding rate up to 8.75 g protein/(kg BW X d) and 99.75 kcal energy/(kg BW X d). Regressing growth rate back to zero resulted in maintenance requirement values of 1.32 g protein/(kg BW X d) and 15.06 kcal energy/(kg BW X d) for experiment 1 and 1.32 g protein/(kg BW X d) and 15.08 kcal energy/(kg BW X d) for experiment 2. Net gains in body protein and energy also increased linearly (r2 = 0.93) with increasing feeding rates up to 8.75 g protein/(kg BW X d) and 99.75 kcal energy/(kg BW X d) in both experiments. Regression equations from these data predicted 1.07 g protein/(kg BW X d) and 17.00 kcal energy/(kg BW X d) in experiment 1 and 1.00 g protein/(kg BW X d) and 17.33 kcal energy/(kg BW X d) in experiment 2 was required to maintain a constant amount of protein and energy in catfish tissue. These requirement values for maintenance and maximum gain agree closely with those predicted from growth data.