Effects Of The Protein Diet Supplemented With Enough Essential Amino Acids And Cysteamine Supplementation On Intestinal Development,Antioxidant And Mucosal Barrier Function In Growing Pigs

Intestinal not only as the animal digestion and absorption of nutrients,but also has barrier functions.The health of the intestines is inseparable from the health of the whole animal.The low protein level diets supplemented with enough essential amino acids can reduce the intestinal digestion burden,save protein resources、reduce nitrogen emissions,and protect the environment.Cysteamine(CS)has the role of promoting animal growth,regulating neuroendocrine,improving antioxidant capacity and enhancing immunity.Hence,the objectives of the present experiment were to study the effects of dietarycrude protein levels and CS supplementation on intestinal development,intestinal antioxidant performance and intestinal mucosal barrier function of growing pigs,thus providing theoretical reference and sciencific guidance for the rational use of low protein level diets supplemented with enough essential amino acids and CS.1.Effects of low protein level diets supplemented with enough essential amino acids and cysteamine supplementation on intestinal development of growing pigsOne hundred twenty barrow(Yorkshire × Landrace × Meishan)pigs with an average initial body weight of 42 kg were randomly allocated into four treatments using the 2 × 2 factorial arrangement with five replicates and six pigs each.The pigs were fed with one of the four diets,as follows:[normal protein level diet(NP)(16%CP),NP supplemented with CS,low protein level diet(LP)(12%CP),and LP supplemented with CS].The pure CS supplementation level was 100 mg/kg.The diet was supplemented with enough EAA to meet the NRC AA requirements of pigs and maintain the balanced supply of eight EAA including lysine,methionine,threonine,tryptophan,valine,phenylalanine,isoleucine,and leucine.The duration of the experiment was 31 days.The results showed that:CS supplementation significant decreased the concentration of somatostatin(SS)in the duodenum and jejunum mucosa(P<0.05),significant increased glucagon-like peptide 2(GLP-2)in the duodenum mucosa and ghrelin in the duodenum and jejunum mucosa(P<0.05).CS supplementation significant increased the villus height(VH)of the jejunum(P<0.05),significant decreased the crypts depth(CD)in the duodenum(P<0.05),significant increased villus height and crypt depth ratio(VH/CD)in the duodenum(P<0.05).CS supplementation significant increased the activity of alkaline phosphatase(AKP)in the jejunum mucosa(P<0.05).CS supplementation significant increased the mRNA relative expression of insulin-like growth factor-1(IGF-1)and insulin-like growth factor-1 receptor(IGF-1R)in the duodenum and jejunum mucosa(P<0.05),and significant increased the mRNA relative expression of epidermal growth factor(EGF)in the duodenal mucosa(P<0.05).CS supplementation did not significant affect on the mRNA relative expression of proliferating cell nuclear antigen(PCNA)in small intestine mucosa(P>0.05).There is no significant effect on dietary protein levels for intestinal development of growing pigs(P>0.05).There were no interactions between dietary protein levels and CS supplementation for intestinal development of growing pigs(P>0.05).2.Effects of low protein level diets supplemented with enough essential amino acids and cysteamine supplementation on the antioxidant capacity and theintestinal mucosa barrier functions in small intestine of growing pigsExperiment design was the same with experiment 1.The results showed that:CS supplementation significant increased the total antioxidant capacity(T-AOC)in the duodenal mucosa and the activity of catalase in the jejunum mucosa(P<0.05),significant increased the activity of glutathione peroxidas(GSH-Px)in small intestine mucosa(P<0.05),and significant decreased the concentration ofthe malondialdehyde(P<0.05).CS supplementation significant increased the mRNA relative expression of the Occludin in thejejunum mucosa and the mRNA relative expression of the ZO-1 in the duodenum and jejunum mucosa(P<0.05).CS supplementation significant increased the concentration of the secretory immunoglobulin A(SIgA)and the mRNA relative expression of the interleukin-2(IL-2)and interleukin-4(IL-4)in the jejunum mucosa(P<0.05),significant increased the mRNA relative expression of the toll like receptor 4(TLR4)in the duodenum and jejunum mucosa(P<0.05).There is no significant effect on dietary protein levels for the antioxidant capacity and the intestinal mucosa barrier functions of growing pigs(P>0.05).There were no interactions between dietary protein levels and CS supplementation for all variables except the mRNA relative expression of the Occludin(P>0.05).