Effects of nonstarch polysaccharide hydrolase of plant protein-based diets on growth, nutrient digestibility, and protease/amylase activities of Yellow River carp, Cyprinus carpio

The purpose of this study was to evaluate the effects of nonstarch polysaccharide (NSP) hydrolase (primarily xylanase and beta-glucanase), present in plant protein-based diets, on growth, nutrient digestibility, and protease/amylase activity of Yellow River carp, Cyprinus carpio var.. Six hundred fish were randomly allocated to four groups in five replicates and fed diets with different NSP enzyme levels (0, 0.025, 0.05, and 0.1%) for 56 days. The addition of 0.05 and 0.1% NSP enzymes to diets significantly improved the specific growth and protein efficiency rates and reduced the feed intake and feed conversion rates (p < .05). The apparent digestibility of dry matter, crude protein, energy, crude fiber, crude ash, and some amino acids was also significantly improved with 0.05 and 0.1% NSP enzymes (p < .05). The protease activity of hepatopancreas in fish fed the diet with 0.1% NSP enzymes was significantly higher than that of the control diet (p < .05). For four sample-collecting time points, except for 5 hr after feeding, the protease activity in the middle-rear intestine of the 0.025% enzyme group was significantly higher than that of the control group (p < .05). Addition of 0.025 or 0.05% NSP enzymes did not affect hepatopancreas amylase activity but increased the amylase activity of the front and middle-rear intestines to a certain extent. However, a high dose of NSP enzymes (0.1%) inhibited hepatopancreas amylase activity. Determination of the effects of NSP enzymes on growth, nutrient digestibility, and endogenous enzyme activity indicated that the addition of 0.05% NSP enzymes in diets is optimal for Yellow River carp.