Effects of dietary phenylalanine on growth, digestive and brush border enzyme activities and antioxidant capacity in the hepatopancreas and intestine of young grass carp (Ctenopharyngodon idella)

Abstract

This study investigated the effects of phenylalanine on growth, digestive and absorptive ability and antioxidant status of young grass carp (Ctenopharyngodon idella). Young grass carp were fed diets containing 3.4 (basal diet), 6.1, 9.1, 11.5, 14.0 and 16.8 g phenylalanine kg À1 diet with a fixed of 10.7 g tyrosine kg À1 diet for 8 weeks. Percent weight gain (PWG), feed efficiency and feed intake of fish were the lowest in fish fed the basal diet (P < 0.05). Trypsin, lipase and amylase activities in the hepatopancreas, and antioxidants including glutathione contents and glutathione reducase activities in the hepatopancreas and intestine were all the highest in fish fed 11.5 g phenylalanine kg À1 diet (P < 0.05). Trypsin, chymotrypsin and amylase activities in whole intestine, and creatine kinase, Na + , K + -ATPase and alkaline phosphatase activities in the proximal intestine, and superoxide dismutase activities in the hepatopancreas and intestine were all the highest when phenylalanine at level of 9.1 g kg À1 diet (P < 0.05). In conclusion, phenylalanine improved growth, digestive and absorptive ability, and antioxidant capacity of young grass carp. The phenylalanine requirement of young grass carp (256-629 g) based on PWG was 10.4 g kg À1 diet or 3.44 g 100 g À1 protein.

Dietary phenylalanine-improved intestinal barrier health in young grass carp (Ctenopharyngodon idella) is associated with increased immune status and regulated gene expression of cytokines, tight junction proteins, antioxidant enzymes and related signalling molecules

“…This study shared the same growth trial with our previously reported by Li et al [8]. The composition of the basal diet is shown in Table 1.…”

“…4 6. impaired digestive and absorptive functions as well as antioxidant capacity in the intestines of young grass carp, but all of these negative observations could be improved by optimal Phe supplementation [8]. In poultry, digestive ability and absorption function rely on intestinal health [48].…”

“…Jian). Our previous study indicated that phenylalanine (Phe) deficiency can reduce antioxidant capacity and aggravate the intestinal lipid and protein oxidation, thereby impairing the structural integrity of the intestine in young grass carp (Ctenopharyngodon idella), whereas Phe supplementation could reverse the negative effects mediated by Phe deficiency [8]. These observations suggested that Phe might influence intestinal mucosal immune function, which requires further investigation.…”

“…To combat oxidative damage, fish are equipped with antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) [28]. Our pervious study indicated that SOD, CAT and GPx activities were improved and intestinal oxidative damage were reduced in young grass carp fed diets of 9.1, 9.1 and 11.5 g Phe kg À1 , respectively [8]. Tiedge et al [29] found that the activity of antioxidant enzyme can be affected by their mRNA levels in the rat intestine.…”

“…Part 1 of these studies showed that Phe could improve the growth performance, digestive ability and absorptive function as well as antioxidant capacity in the intestine of young grass carp [8]. Fish growth is related to digestive and absorptive functions which rely on intestinal health [35].…”