Effect Of Low Protein Diet And Cysteamine Supplementation On Oxidative Stress In Weaned Piglets

Piglets are very vulnerable to intestinal oxidative stress after weaning.Lowprotein amino acid balanced diets can effectively reduce the symptoms of feed protein indigestion and reduce stress responses in weaned piglets.Cysteamine is currently used as a new type of growth promoting feed additives and has been widely used in livestock production.The chemically modified novel cysteamine overcomes the disadvantages of its own thiol instability and ensures its active ingredient in feed additives.However,most of the current studies on cysteamine are based on the study of growth performance under normal diet conditions.It has rarely been reported that whether adding cysteamine in low-protein diets can alleviate oxidative stress in piglets.Therefore,this study intends to add different levels of novel chemically modified cysteamine to low-protein amino acid balanced diets(CP 17%)to explore the effects of novel chemically modified cysteamine on the performance and nutrient digestibility of weaned piglets;Another aim of this study is to establish an oxidative stress model for weaned piglets(challenged with Diquat)to study the effect of different doses of cysteamine in low-protein amino acid balanced diets on the oxidative stress relief of weaned piglets,and to provide a theoretical basis for the development of new feed additives for piglets.A total of 30 twenty-eight-day-old weanling pigs with a similar weight(7.15±0.14 kg)were randomly assigned to 5 groups,with 6 in each group.The five groups were Control group,Diquat group,CS 60 group,CS 80 group and CS 100 group,respectively.Piglets in Control group and Diquat group were fed a low nitrogen diet(CP 17%).And piglets in CS 60 group,CS 80 group and CS 100 group were fed a low nitrogen containing 60 mg/kg,80 mg/kg,and 100 mg/kg of CS for 28 days.On the 29 th day,piglets in the Diquat group and three CS groups were injected with 10 mg/kg BW Diquat,and the piglets in Control group were injected with the same amount of saline.All the piglets were slaughtered and sampled on the 34 th day.The results showed that dietary supplementation of cysteamine in low-nitrogen diets had no significant effect on the daily weight gain,daily feed intake,and feed /gain ratio of piglets at 0-28 d.The best effect of growth performance was obtained with piglets fed the dietary CS of 60 mg/kg without significant changes(P>0.05).The supplementation of cysteamine in low-nitrogen diets increased the energy digestibility,total nitrogen utilization,and nitrogen digestibility of piglets(P>0.05).Serum ALT,AST,GGT,and ALP levels of piglets in CS 60 group and CS 80 group had a tendency to decrease compared with the control group,and there was no significant effect of cysteamine levels on TP,ALB,BUN,NH3 L,TG,TC,HDL,LDL-C3,GLU,AMS and LDH levels of piglets in CS 60 and CS 80 group compared with Control group(P>0.05).Dietary supplementation with different doses of cysteamine increased the total amino acid content(P>0.05);The total essential amino acids of piglets in CS 60 group and CS80 group and CS 100 group was significantly increased(P<0.05);The total essential amino acid EAA/total non-essential amino acid NEAA ratio in CS 60 group and CS 100 group were significantly increased(P<0.05);And branched-chain amino acid BCAA/aromatic amino acid AAA in CS 60 group was increased(P>0.05).It shows that a proper dose of cysteamine has a role in promoting the absorption and metabolism of nutrients in piglets.At 29d-34 d,the spleen index of piglets in CS60 group was significantly increased compared with Diquat group(P<0.05),and the spleen index and kidney index of piglets in CS80 group was slightly increased(P>0.05).This indicates that cysteamine may promote the immune function of piglets subjected to oxidative stress to a certain extent.In terms of serum indexes,the serum GSH content in the anterior vena cava of piglets in CS 60 group was slightly higher than that in Diquat group(P>0.05).The GSH content and GSH-px activity in CS80 group were significantly increased(P<0.05).The serum T-AOC levels in the hepatic portal vein of CS 60 group was increased significantly(P<0.05).The serum GSH and T-AOC contents in the portal vein of CS 80 group increased significantly(P<0.05).Compared with Diquat group,liver GSH-Px activity was significantly increased(P<0.05),and GSH-Px activity in CS 80 group was significantly increased(P<0.05).Compared with Diquat group,the MDA content in kidneys of CS 60 group and CS 80 group was slightly decreased compared with Diquat group(P>0.05).Compared with Diquat group,GSH content of longissimus dorsi muscle in CS60 group was significantly increased(P< 0.05),T-SOD activity in CS 80 group was significantly increased(P<0.05).In summary,CS has a certain role in improving the body’s antioxidant defense ability.In summary,the addition of cysteamine in low-nitrogen diets can be beneficial to the promotion of digestion and absorption of nutrients in piglets to a certain extent,and had no negative effect on the liver of piglets.CS B60 group obtained the best growth performance(1-28 d).After intraperitoneal injection of Diquat(29-34 d),the effect of CS cysteamine on kidney was superior to the effect on other tissues and organs.The effect of cysteamine on relieving oxidative stress on pigs in production practice still needs to be further explored.