Effects of Fishmeal Replacement by Mixture of Soybean Meal and Rapeseed Meal on Digestive Enzyme Activities and Apparent Digestibility of the Black Carp (Mylopharyngodon piceus)

This study was conducted in a water flow-through tank to evaluate the effects of dietary fish meal(FM) replacement by mixture of soybean meal(SBM) and rapeseed meal(RSM) on digestive enzyme ac-tivities and apparent digestibility of black carp(Mylopharyngodon piceus).A typical diet with 38% crude pro-tein level(fishmeal protein: plant protein =1:1) was used as the control(Diet A).The other experimental diets(Diets B-E) in which 25%,50%,75% and 100% of fishmeal protein were replaced by mixture of soybean meal and rapeseed meal(SBM: RSM =1:1) respectively.Five triplicate groups of fish were fed the isocaloric(13.3 kJ/g feed energy) and isonitrogenous(38% crude protein) diets three times per day at 5% of fish body weight for 8 weeks,and each experimental group was stocked with 20 fish [initial average weight of(10.45 ± 0.85) g].The apparent digestibility of formulated diets was estimated based on feces analysis of the black carp in laboratory.The results showed that the protease activity in intestine and hepatopancreas of diet A,diet B and diet C was significantly higher than those of diet E(P0.05),but no significant difference was found among three diets(P0.05).There was no significant difference for amylase activity in intestine and hepatopancreas of black carp in five different experimental groups(P0.05).Apparent digestibility of protein、lipid and dry matter were not changed significantly(P0.05) among diet A、diet B and diet C,but the apparent digestibility were reduced sig-nificantly as the proportion of plant protein in the diets continually increased.The results indicated that dietary fish meal(FM) protein replacement by 25%-50% mixture protein of soybean meal(SBM) and rapeseed meal (RSM) caused no significant effect on the digestive enzyme activity and apparent digestibility of black carp.