| Heat stress caused by high temperature and necrotizing enteritis caused by Clostridium perfringens are two major challenges to poultry production,and they often occur simultaneously in broiler production.High temperature and Clostridium perfringens can increase intestinal permeability,damage intestinal function and reduce immunity,and caused reduction in feed intake and growth rate of poultry,resulting in great economic losses.In this study,the effects of Clostridium perfringens administration under high temperature conditions on immune cells,immune factors in blood and jejunum and cecum microbe composition of Qingyuan chickens.The results of this study may provide theoretical basis for revealing the molecular mechanism of intestinal immune damage induced by high temperature in poultry.A total of 192 healthy 20d Qingyuan chickens with similar body weight were randomly divided into normal temperature control group(CON group,25~oC,10h,paired feeding),normal temperature+Clostridium perfringens group(CP group,25~oC,10h,paired feeding,Clostridium perfringens type A(1m L 2×10~8cfu/m L)),high temperature group(HT group,35~oC,10h,free feeding),high temperature+Clostridium perfringens group(HT+CP group,35~oC,10h,free feeding,Clostridium perfringens type A(1m L 2×10~8cfu/m L)).There were 4 groups with 12 replicates of 4chckens each.Chickens from normal temperature was paire-fed diets equal to that of high temperature group.The experiment lasted for 17 days(21d～37d).During the experimental period of 21d～37d,chickens were susceptible to high temperature or normal temperature,and then chickens were treated with bacteria for four consecutive days(31d～34d)on the basis of temperature treatment.At 37 days of age,3m L blood and 1.0cm jejunum tissue were collected for flow cytometry,and another 1.0cm jejunum segment was taken and fixed in paraformaldehyde solution.The plasma,jejunal mucosa and the whole segment were stored at-80℃.Daily feed intake was recorded during the experiment,and Qingyuan chickens were weighed at 20d,30d and 36d.The results are shown as follows:(1)High temperature significantly reduced the body weight of Qingyuan chickens of30d and 36d,and significantly increased the ratio of feed to gain at 30d～36d(P<0.05);(2)The positive rate of CD3~+,CD4~+,CD3~+4~+,CD4~+8~+T cells and the ratio of CD3~+4~+/CD3~+8~+in the blood of Qingyuan chickens from CP group were significantly higher than those in CON group(P<0.05),while these T cell indexes from HT+CP group were consistent with those in CON group(P>0.1).HT had no significant effect on T cells(P>0.1).(3)The plasma concentrations of IL-6 and IL-10 in HT+CP group were significantly lower than those in CP group(P<0.05),and the plasma cortisol concentration in HT+CP group was significantly higher than that in CON group(P<0.05).The plasma concentration of TNF-αin HT group was significantly increased in comparison to CON group(P<0.05),the plasma Ig M concentration in CP group,HT group and HT+CP group was significantly increased as compared to CON group(P<0.05).(4)Compared with CON,the villus height and the ratio of villus height/crypt depth of Qingyuan jejunum in HT and HT+CP groups were significantly decreased(P<0.05),the villus height and the ratio of villus height/crypt depth of HT+CP group was decreased compared with CP group(P<0.1).(5)The positive rates of CD3~+4~+,CD3~+8~+and CD4~+8~+T cells in Qingyuan jejunum in HT+CP group were significantly higher than those in CON,CP and HT groups(P<0.05).Compared with CON group,the CD3~+4~+/CD3~+8~+ratio of Qingyuan chicken jejunum in HT group was significantly increased(P<0.05).(6)Compared with the CON group,the m RNA expression of IL-10 in jejunal mucosa from CP group was significantly increased(P<0.05),while that of HT+CP group was significantly decreased(P<0.05).The m RNA expression of IL-10 in jejunal mucosa and jejunum from CP group was significantly higher than that from HT and HT+CP groups(P<0.05).The m RNA expressions of IL-8,NF-κB,HT and HT+CP groups were significantly increased in jejunum mucosa(P<0.05),while either high temperature or CP had no significant effects on the inflammatory factors in jejunal mucosa(P>0.1).The SIg A of CP group was increased compared with CON(P<0.1).(7)High temperature or CP significantly changed the cecal microflora compositoin in Qingyuan chickens,with the dominant Lactobacillus decreased and Bacteroides increased,the beneficial bacteria Rikenellaceae＿RC9＿gut＿group decreased and the pathogenic bacteria Escherichia-Shigella increased.The Chao and Otus indices of cecal microorganisms from HT+CP group were significantly decreased(P<0.05).LEf Se analysis showed that Bacillales,Bacillaceae and Bacillus were the major Biomarker in CP group,while Listeriaceae and Listeria were the major Biomarker in HT+CP group.In conclusion,high temperature significantly reduced the growth performance of Qingyuan chickens,impaired jejunal morphology,while CP induced blood adaptive immune response and humoral immunity of Qingyuan chickens.High temperature or CP caused jejunal mucosal inflammation and changed the intestinal flora composition of Qingyuan chickens.CP administration under high temperature decreased the immne response of blood T cells and caused the rapid expansion of jejunum T cells. |
