Effect of reducing dietary digestible energy to protein ratio on weight gain and body fat of juvenile channel catfish Ictalurus punctatus.

摘要

A laboratory feeding trial was conducted to evaluate the effects of reducing DE to protein (DE:P) ratios of practical diets on body fat and weight gain of channel catfish. Five diets were formulated to contain 32, 28 or 24% CP with typical DE:P ratios of 8.5, 9.9 and 11.4 kcal/g protein, respectively, and 28 or 24% protein with a reduced DE:P ratio of 8.5 kcal/g protein. Cellulose was used to adjust the DE:P ratio. Juvenile I. punctatus, initial weight 5.2 g, were fed the experimental diets twice daily to apparent satiation for 12 weeks. Fish fed on the 28% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein gained less weight and converted feed less efficiently than those fed on the 28% protein diet with a typical DE:P ratio of 9.9 kcal/g protein. Fish fed on the 24% protein diet with a reduced DE:P ratio of 8.5 kcal/g protein had a similar weight gain but converted feed less efficiently than those fed on the 24% protein diet with a typical DE:P ratio of 11.4 kcal/g protein. Weight gainand feed conversion efficiency of fish fed on the 32% protein diet with a typical DE:P ratio of 8.5 kcal/g protein were higher than for fish fed other diets except those fed on the 28% protein diet with a DE:P ratio of 9.9 kcal/g protein. There were nodifferences in feed intake and survival among dietary treatments. Fillet fat of fish fed on the 24 and 28% protein diets with a reduced DE:P ratio was lower than that of the fish fed on diets containing the same protein concentrations with typical DE:P ratios. At a DE:P ratio of 8.5 kcal/g protein, there were no differences in fillet fat concentration among fish fed diets containing different protein concentrations. There were no differences in fillet protein, moisture and ash between fish fed on the 24or 28% protein diets containing reduced and typical DE:P ratios. The results show that reducing DE:P ratios in practical diets lowers body fat but also reduces weight gain of channel catfish; thus it would not be economical to use this strategy to reduce body fat of the fish.