Effects Of Lactobacillus Rhamnosus On Growth Performance?Intestinal Morphology And Immune Function Of Broilers Under Immune Stress

In production practice,animals are often stimulated by various pathogens and artificial immune antigens,which will lead to the occurrence of immune stress.Immune stress can cause anorexia,slow growth,decreased immune function and so on.Lactobacillus rhamnosus MLGA used in this experiment was isolated from the digestive tract of healthy chickens.Our research group found that Lactobacillus rhamnosus MLGA can improve the growth performance of broiler chickens,improve the natural immunity of the body,and have good probiotics.In this study,sanhuang chicken was taken as the research object,and the lipopolysaccharide(LPS)immune stress model was adopted for feeding experiment to investigate the effects of dietary Lactobacillus rhamnosus MLGA on growth performance,serum related biochemical indexes,small intestine morphological structure and immune-related gene expression in broilers under the condition of immune stress and the mechanism of action.252 healthy 1-day-old sanhuang chickens(females)with similar weight were randomly divided into 3 treatment groups,each treatment with 6 repeats and each repeat with 14chickens.The three treatment groups were the control group,LPS stimulation group and Lactobacillus rhamnosus+LPS group.The LPS group was fed basic diet,and repeated intraperitoneal injection of LPS at 14,16,18 and 20 days old,dissolved with normal saline before injection.Injection doses:14 days old(300?g/kg body weight),16 days old(400?g/kg body weight),18 days old(500?g/kg body weight),20 days old(600?g/kg body weight).The injection amount was 0.5ml/chicken.The control group was fed basic diet,and the corresponding volume of normal saline was injected at the corresponding age.Lactobacillus rhamnosus+LPS group was fed basic diet with 1×10~9cfu/kg Lactobacillus rhamnosus MLGA,and the immune stress treatment was the same as the LPS group.A chicken was randomly selected from each group at 21 and 28 days of age,heart blood was collected,serum was isolated,and serum related biochemical indexes were determined by ELISA.The duodenum,jejunum and ileum were collected for paraffin section and hematoxylin-eosin(HE)staining to determine the morphological structure of small intestine.Ileum mucosa was collected to determine the expression level of tight junction protein.Ileum,spleen and bursa were collected to measure the expression of immune-related genes.The test results are as follows:1.LPS-induced immune stress significantly increased the feed weight ratio of broilers aged 21-28 days and 21-35 days(P<0.05).Dietary addition of Lactobacillus rhamnosus MLGA showed a tendency to increase the average daily weight gain of broilers at 21-35days of age under the condition of immune stress(P=0.084).2.LPS-induced immune stress significantly increased serum levels of interleukin-1?and IL-12(P<0.01)and corticosterone(CORT),IL-2 and IL-6(P<0.05 or P<0.01)in broiler chickens at the 21st day of age,and significantly reduced the content of IL-8(P<0.01)and IL-10(P<0.05)at the 28th day of age.Dietary addition of Lactobacillus rhamnosus MLGA significantly increased serum IL-10 content in broilers at the 21st day of immune stress(P<0.05),and decreased serum IL-6(P=0.070)and IL-8(P=0.076)at the 28th day of immune stress.3.LPS-induced immunological stress significantly reduced the 21st day age of poultry in jejunum and back length,the ratio of length and crypt depth,and 28 days of age duodenum and jejunum villus length and the ratio of crypt depth(P<0.05),and significantly improve the 21st day age ileal crypt depth and the age of 28,duodenum and jejunum crypt depth(P<0.05).Dietary addition of Lactobacillus rhamnosus MLGA significantly reduced immune stress conditions of the first 21 days of age chicken ileal crypt depth and 28 days of age duodenum and jejunum crypt depth(P<0.05),and significantly improve the day age back to 21 in the ratio of the length and the crypt depth and 28 days of age duodenum,jejunum villus length and the ratio of crypt depth and duodenum villus length.LPS-induced immune stress significantly reduced the expression of Occludin,Occludin and ZO-1 in ileum mucosa of broilers at the 21st day of age,as well as the mRNA expression of Occludin at the 28th day of age(P<0.05).Dietary addition of Lactobacillus rhamnosus MLGA significantly increased the expressions of Claudin-1,Occludin and ZO-1 mRNA in ileum mucosa of broilers at 21 days old and 28 days old under immune stress conditions(P<0.05).4.LPS-induced immunological stress significantly improved the 21st day age chicken ileum TLR2,TNF-?,28 days of age ileum TNF-?,21days of age spleen IL-1?,21days of age bursa of fabricius CATH-3,IL-1?,IL-12,bursa of fabricius of A20 day age 28,IL-1?,IL-12,TNF-?mRNA expression(P<0.05),and significantly reduce the ileum CATH-3 day age 21 and bursa of fabricius of A20 day age 21 mRNA expression(P<0.05).Dietary addition of Lactobacillus rhamnosus MLGA significantly reduced the mRNA expression of ileum TLR2,IL-12,TNF-?,spleen,and ileum IL-1?,as well as the mRNA expression of ileum A20,IL-1?,and IL-10 at the 28th day of age in broilers under the condition of immune stress(P<0.05),and significantly increased the mRNA expression of ileum A20,spleen at the 28th day of age(P<0.05).In conclusion,LPS-induced immune stress reduces growth performance of broiler chickens,increases the content of pro-inflammatory cytokines in serum,reduces the content of anti-inflammatory cytokines in serum,destroys intestinal barrier,and changes the expression of immune-related genes in the body.Dietary addition of 1×10~9cfu/kg Lactobacillus rhamnosus MLGA can improve the immune stress under the condition of broiler growth performance,reduce the serum levels of proinflammatory cytokines,increase the serum levels of anti-inflammatory cytokine in the intestinal injury,by regulating the immune related genes expression of build up the body on the immune stress resistance,reduce the damage to the body's immunological stress.