Interactions between dietary protein level and feeding regime on body composition, digestive enzyme activities, plasma metabolites in African catfish Clarias gariepinus (Burchell, 1822).

摘要

An 8-week feeding trial was conducted with African catfish fingerlings (triplicate groups of 20 fish average weight ~14 g per 30 L tank, 28+or-1 degrees C) to investigate the interactions between feeding regime and dietary protein level on body composition, digestive enzyme activities, plasma metabolites and liver histology. Three fishmeal based diets with three protein levels (28, 35 and 40%) and gross energy levels of 14.42, 17.71 and 20.08 kJ.g-1 GE respectively. The diets contained a P/E ratio of 20-mg protein kJ-1 GE and L/CHO ratio (g/g) of 0.40. Fish were fed each diet to appetite or to a restricted feeding regime. Restricted feeding was performed by offering fish decreasing fixed rate of 5.0, 4.1 and 3.5% of their body weight of diets 28, 35 and 40% protein respectively per day adjusted fortnightly. Body carcass composition had no influence on dietary protein level or feeding regime. Protease and lipase activities (intestine and liver) under either restricted or appetite feeding did not change significantly (P>0.05) in fish fed different dietary protein levels. No significant differences were detected on plasma concentrations (glucose, triglycerides and cholesterol), plasma amino acid level and histology of liver at different protein levels in both feeding regime. This result suggests that the response of African catfish to change in protein levels is not influenced by feeding regime.