Effects of dietary fiber levels on growth, biochemical indexes and intestinal health of Cyprinus carpio var.jian

An 8-week feeding trial was conducted to evaluate the effects of dietary fiber on growth performance, plasma biochemical indexes, intestinal histology, and structure of intestinal bacteria of juvenile Jian carp (Cyprinus carpio var. jian). Five isonitrogenous and isolipidic diets were formulated to contain 1.8%, 5.2%, 8.8%, 12.2% and 15.8% cellulose, respectively. The results indicated that Jian carp fed the diets containing 8.8% fiber had significantly higher weight gain rate(WGR)、specific growth rate (SGR) and protein efficiency ratio (PER) than those fed the other fiber diets, while plasma alanine amiotransferase (ALT) and aspartate transaminase (AST) activities significantly decreased. Viscerosomatic index (VSI), hepatosomatic index (HSI), triglyceride (TG), total cholesterol (TC) and glucose (GLU) contents significantly decreased with increasing dietary fiber levels. Compared to the control, the carnitine palmitoyltransferase I (CPT-1), adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) and peroxisome proliferator–activated receptor (PPAR-α) activities in liver significantly increased in fish fed the diets with 5.2%, 8.8% or 12.2% fiber levels. Moreover, the histological structures of midgut and hindgut were impaired in fish with 15.8% fiber, and the intestinal microbial ecosystem investigation showed an beneficial effects at a higher supplemental level (15.8%), and improvement in liver histostructure at high fiber levels. These findings indicated that dietary fiber levels could improve liver function and intestinal health of Jian carp; also, higher dietary fiber levels have a positive impact and decrease the potential risk of disease in Jian carp. Based on SGR, a dietary fiber level of 9.19% was optimal for growth performance of juvenile Jian carp.