| Weaning is the biggest stress response after piglets are born.How to improve the growth performance and immune function of weaned piglets and reduce weaning stress have always been the focus of animal husbandry science and technology workers.Dendritic cells(DCs)are currently the most powerful antigen-presenting cells in vivo.Arginine(Arg)plays an important role in improving piglet growth performance,immune function and promoting DCs differentiation and maturation.However,the effects of weaning on DCs differentiation and mediated intestinal mucosal immune function and the regulation of Arg on DCs in weaned piglets and their regulation of intestinal mucosal immune function have not been reported.In this experiment,piglets were used as animal models,and DCs were the focus of research.The effects of weaning on DCs-mediated intestinal mucosal immune function in weaned piglets and the regulation of Arg supplementation during lactation were studied.Experiment 1:Effect of weaning on DCs-mediated intestinal mucosal immune function in pigletsIn this experiment,40 healthy Duroc × Landrace ×Yorkshire piglets with similar body weight at 21 days old,half male and female pigs were randomly divided into two groups,20 in each group,the two groups were suckling group(S group)and weaning group(W group).S group piglets were continuously milked at 21 days of age and continued to breastfeed and W group piglets were weaned at 21 days of age and fed regular piglet diets.Eight piglets were randomly selected from each group 3d after weaning and 7d after weaning,and slaughtered for sampling.Growth performance,intestinal morphology,number of T cells,number of DCs,immune index,and expression levels of key genes in the Notch2 signaling pathway were measured.The results show:(1)Compared with the S group,the body weight of the W group was significantly decreased at 3d and 7d after weaning(P<0.01).At 3 days after weaning,the serum LDH content of group W was significantly increased(P<0.05),the jejunum and ileum villus height and villus surface area of group W were significantly decreased(P<0.05),crypt depth was significantly increased(P<0.05),and V/C was significantly decreased(P<0.05).At 7 days after weaning,the jejunum villus height,villus width and villus surface of group W were significantly decreased(P<0.01).(2)Compared with the S group,the number of CD3+ T cells in the blood of the W group was significantly decreased(P<0.05),the number of CD3 T cells in the thymus and spleen was significantly increased(P<0.05)and the CD3+CD4+/CD3 CD8+T cell ratio was significantly decreased(P<0.05),and the number of CD3 CD4 T cells in the thymus was significantly decreased(P<0.05).(3)Compared with the S group,the number of CDllb CD16+,SWC3a CD86+,SWC3a SLA-II-DR DCs in group W was significantly decreased at 3 days after weaning(P<0.05).(4)Compared with the S group,at 3 days after weaning the IL-2 content in the serum of the W group was significantly increased(P<0.01),the contents of slgA,IL-2 and IL-10 in jejunum mucosa were significantly decreased(P<0.05)and the content of IL-1? was significantly increased(P<0.05),the content of IL-2 and the gene expression of IL-2 and IL-4 in ileal mucosa were significantly increased(P<0.05)and IL-10 levels were significantly decreased(P<0.05).At 7 days after weaning,the content of IL-2 and the gene expression of IL-12 and IFN-y in jejunum mucosa were significantly increased(P<0.05)and IL-10 content and IL-4 gene expression were significantly decreased(P<0.05),the IL-1? level in the ileum mucosa was significantly decreased(P<0.01),and the expression levels of IL-2 and IFN-y genes were significantly increased(P<0.05).(5)Compared with the S group,the expression of Jagged1 gene in the ileal mucosa of group W was significantly decreased 3 days after weaning(P<0.01),At 7 days after weaning,the expression levels of Notch2 and Jaggedl in jejunum mucosa of group W were significantly decreased(P<0.05),and the expression of D111 gene in ileal mucosa was significantly decreased(P<0.05).It can be seen that after weaning,the intestinal structure of the piglets is impaired,the secretion of proinflammatory cytokines in the intestinal mucosa is increased,the secretion of immunoglobulins and anti-inflammatory cytokines is decreased,the T lymphocyte subsets are unbalanced,and the differentiation and maturation of DCs are inhibited.The 3-day immune stress was greater than 7 days after weaning.The expression of Notch2 signaling pathway in intestinal mucosa of piglets was inhibited after weaning.Intestinal mucosal immune function damage and DCs differentiation induced by weaning stress in piglets may be related to Notch2 pathway.Experiment 2:Regulation of Arg on DCs-mediated intestinal mucosal immune function in weaned pigletsIn this experiment,40 healthy Duro × Landrace ×Yorkshire piglets with similar body weight at 7 days old,half male and female pigs were randomly divided into two groups,20 in each group,the two groups were control group(C group)and arginine group(A group).At 7 days of age,in the case of natural breastfeeding,group C was given 40 mL of 0.9%normal saline daily,and group A was given Arg 40 mL daily(250 mg/kg/d).Weaned at 21 days of age and fed regular compound feed.Weaned at 21 days of age and fed regular compound feed.Eight piglets were randomly selected from each group on the day of weaning(21 d)and 3d(24d)after weaning,and slaughtered for sampling.Growth performance,intestinal morphology,number of T cells,number of DCs,immune index,and expression levels of key genes in the Notch2 signaling pathway were measured.The results show:(1)Feeding Arg during lactation,it significantly increased body weight and ADG at weaning day and 3 days after weaning(P<0.05),significantly increased spleen index and the NO and NOS levels of serum and ileum mucosa at weaning day(P<0.05),significantly increased the LDH activity and NOS content in jejunum and ileum mucosa and the NO content in ileal mucosa at 3 days after weaning(P<0.05).Feeding Arg during lactation,it significantly increased the jejunum villus height and V/C,the ileum V/C and villus surface area(P<0.05),and significantly reduced ileum crypt depth(P<0.01).At 3d after weaning,the jejunum height,V/C and villus surface area of piglets were significantly increased(P<0.05).(2)Feeding Arg during lactation significantly increased CD3+CD4+/CD3+CD8+ T cell ratio in thymus and spleen at weaning day(P<0.05),significantly increased CD3+CD4+ T cells in thymus and CD3+CD8+ T cells in spleen at 3 days after weaning(P<0.05).(3)Supplementation of Arg during lactation significantly increased the number of CD11b+CD16+,SWC3a+CD1a+,SWC3a+CD86+,SWC3a+SLA-II-DR+DCs in the ileum at weaning day(P<0.05).(4)Arg supplementation during lactation significantly increased IgG content in serum,sIgA and IL-10 levels in jejunum and ileum mucosa(P<0.05),significantly reduced IFN-y content in serum,IL-1? and TNF-a gene expression in jejunum mucosa,IL-2 and IL-12 content and IL-2 and IFN-y gene expression in ileum mucosa(P<0.05).At 3 days after weaning,sIgA content in jejunum mucosa and sIgA,IL-10 content and IL-10 gene expression in ileum mucosa were significantly increased(P<0.05),significantly decreased IFN-? content and IL-12 gene expression in jejunum mucosa and the amount of IL-1?and the gene expression IL-1? and IL-12 in the ileum mucosa(P<0.05).(5)Feeding Arg during lactation significantly increased the expression of Notch2 gene in jejunum mucosa and D111 and Jaggedl gene expression in ileum mucosa at weaning day(P<0.05),and significantly increased Dll1 and Hes1 gene expression in jejunum mucosa and Notch2 gene expression in the ileum mucosa at 3 days after weaning(P<0.05).It can be seen that feeding Arg during lactation can improve the growth performance of piglets and reduce the weight loss of weaning.It can reduce the immune stress caused by weaning by reducing the secretion of pro-inflammatory cytokines,increasing the secretion of anti-inflammatory cytokines and immunoglobulins,and Promote differentiation of T lymphocytes and DCs in weaned piglets.Feeding Arg during lactation can promote the expression of key genes in Notch2 signaling pathway.The regulation of Arg on the differentiation of T lymphocytes and DCs in weaned piglets may be related to Notch2 signaling pathway.In summary,weaning can lead to impairing intestinal structure and mucosal immune function in piglets,imbalance of T lymphocyte subsets,decreasing number of mature DCs,inhibition of Notch2 signaling pathway gene expression,and the immune stress caused by weaning 3 days after weaning is more serious.Feeding Arg during lactation can improve the growth performance of piglets,reduce the weight loss of weaning,improve the intestinal mucosal immune function of weaned piglets,and promote the differentiation of T lymphocytes and DCs in weaned piglets.Promoting the expression of key genes in the Notch2 signaling pathway,the regulation of Arg on the differentiation of T lymphocytes and DC cells in weaned piglets may be related to the Notch2 signaling pathway. |
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