Effects Of α-ketoglutarate Supplementation On Nitrogen Metabolism, Antioxidant Capacity And Intestinal Mucosal Morphology And Function Of Songpu Mirror Carp(Cyprinus Carpio)

This experiment was aimed to study the effects of α-ketoglutarate(AKG) supplementation in different protein sources diets on nitrogen metabolism, antioxidant capacity, intestinal mucosal morphology and function and the mechanism of Songpu mirror carp. Two kinds of protein diets(soybean meal protein source, fish meal and soybean meal compound protein source) and two levels of AKG(0 and 1.5%, respectively) at each diets were utilized, the protein level was 28%. A total of 400 Songpu mirror carp with an average initial body weight of(217.93±0.78)g were divided into 4 groups with 5 replicates per group and 20 fish per replicate. The experiment lasted for 10 weeks. The results showed as follows:(1)Diets with AKG significantly improved the protein efficiency ratio(PER) and decreased the feed conversion rate(FCR)(P<0.05). Besides, AKG significantly decreased moisture and crude fat content, and significantly increased the crude protein content in the muscle of Songpu mirror carp(P < 0.05). The protein source and the concentration of AKG had a significant interaction influence on muscle crude ash(P < 0.05), growth performance and other ingredients had no significant interaction effect(P >0.05).(2)AKG significantly improved the alanine aminotransferase(ALT) and aspertate aminotransferase(AST) activity, and significantly reduced the content of uric acid(UA) and triglyceride(TG) in serum(P< 0.05). Other biochemical indexes and diamine oxidase(DAO) activity, blood ammonia and D- xylose content had no significant effect(P >0.05). The protein source and the concentration of AKG interaction had a significant influence on albumin(ALB) and UA content(P < 0.05), other indexes had no significant effects(P > 0.05).(3)Fold height of foregut and villus length of hindgut were significantly improved by AKG, so was the Na+,K+-ATPase activity of foregut(P<0.05). However, the protein source and AKG interaction had no significant influence on intestine morphology and Na+,K+-ATPase activity(P > 0.05).(4)Diets with AKG significantly improved the content of glutathione(GSH) and superoxide dismutase(SOD) activity in foregut and serum(P < 0.05), malondialdehyde(MDA) content in foregut, midgut and serum was significantly decreased by AKG(P<0.05).There have not found any significant effect on the liver and muscle antioxidant indicators by AKG(P > 0.05). The protein source and AKG had a significant interaction influence on serum SOD activity(P<0.05).(5)Diets with AKG significantly improved the activity of protease and lipase in foregut and midgut(P < 0.05). The protein source and AKG had a significant interaction influence on protease activity of hindgut(P<0.05).(6)The content of Glutamate(Glu) and glutamine(Gln)in foregut and hindgut were significantly improved by AKG(P<0.05). Besides, the glutamine synthetase(GS) activity of foregut, liver and serum were also significantly improved by AKG(P<0.05). The protein source and AKG had a significant interaction influence on foregut GS activity and hindgut Glu content(P<0.05).(7)Diets with AKG significantly improved the content of lysine(Lys), total amino acid(TAA) and essential amino acids(EAA), half essential amino acids(HEAA) and non-essential amino acids(NEAA) in muscle and serum(P < 0.05). Besides, The content of threonine(Thr), serine(Ser), alanine(Ala), arginine(Arg), proline(Pro) and delicious amino acids(DAA) of muscle(P<0.05). The protein source and AKG had a significant interaction influence on the content of Thr of muscle(P<0.05).(8)The GS gene expression of intestinal was significantly improved by AKG, while Rhag and Rhbg gene expression of gill was decreased(P<0.05). The protein source and AKG had a significant interaction influence on the gene expression of GS and Rhag and Rhbg(P<0.05).It is concluded that supplementation of 1.5% AKG has a positive effect on the protein utilization rate and intestine development, AKG can also promote digestive enzyme activities, antioxidant capacity and enhance the metabolism and synthesis of Songpu mirror carp. Besides, it also improve the fish ammonia nitrogen metabolism and the related gene expression, so was the composition and content of muscle and serum amino acid, then improve the protein deposition of Songpu mirror carp.