Effects Of Bacillus Subtilis On Performance And Intestinal Health Of Yellow-feather Broilers Challenged By Pathogen

This experiment was conducted to investigate the effects of Bacillus subtilis（QST713）on the growth performance and intestinal health of yellow-featherbroilers challenged by coccidium or Clostridium perfringens,and to determine whether the probiotic additive can alleviate intestinal damage caused by coccidium or Clostridium perfringens.A total of 600 one-day-old young broiler cockerels Ephedra Weni No.4 were ran-domly divided into 5 groups:Con blank group,CIC.p group（10 times immune dose coccidium+Clostridium perfringens challenge for 3 consecutive days）,CIC.p+BS group(CIC.p group+100 mg/kg Bacillus subtilis,1.0×10¹⁰CFU/g),C.p group（C.p challenge for 7 consecutive days group）,C.p+BS group(C.p group+100 mg/kg Ba-cillus subtilis,1.0×10¹⁰CFU/g),There were 6 replicates per treatment and 20 repli-cates per replicate.All chickens were immunized with coccidia vaccine 5 days later,and the rest were immunized normally,Clostridium perfringens at 3×10⁸CFU/ml/bird/day by instillation.The first period was fed with meal and the second and third period was fed with pellets,and the experiment lasted for 80 days.The results are as follows:（1）Challenge treatment:（1）Compare with the control group,CIC.p group signifi-cantly decreased the 42d and 80d BW,22-42d and 1-80d ADG（P<0.05）,signifi-cantly increased 22-42d and 1-80d F/G（P<0.05）;significantly decreased the 42d se-rum TP and ALB level,HDL-C concentration（P<0.05）;significantly decreased the 42d serum GSH-PX activity（P<0.05）,significantly increased 35d and 42d serum MDA centent.There was no significant effect on organ index and intestinal length（P<0.05）.Duodenum,jejunum and ileum scores were significantly increased on 35d and 42d（P<0.05）;significantly decreased 35d jejunum VH,ileum VH and VH/CD（P<0.05）;significantly up-regulated the expression of Claudin-1 and IL-4 mRNA in jejunum on 35d,and significantly down-regulated the expression of IL-10 mrna in ileum on 35d（P<0.05）;the relative abundations of 35d cecum proteobacteria,pseu-domonas,42d cecum bacaeroides and[Ruminococcus]＿torques＿group were signifi-cantly increased,while the relative abundations of 35d cecum Romboutsia,42d cecum bacteroides,allocladobacteria and lactobacillus were significantly decreased（P<0.05）;（2）Compare with the control group,C.p group significant decreased 1-80d death rate（P<0.05）;serum 42d TP and ALB level,TC concentration and HDL-C concen-tration were significantly decreased（P<0.05）;serum 42d GSH-PX activity were significantly decreased（P<0.05）.The 35d spleen index was significantly increased（P<0.05）;the 35d length of jejunum and ileum was significantly reduced（P<0.05）.Duodenum,jejunum and ileum scores were significantly increased on 35d and 42d（P<0.05）;42d serum DAO concentration was significantly increased（P<0.05）;sig-nificantly increased ileum VH and CD（P<0.05）;significantly up-regulated Clau-din-1 mRNA expression in 42d ileum and significantly down-regulated IL-10 mRNA expression in 35d ileum（P<0.05）;the relative abundances of Coproecium and Cladomyces on 35d were significantly increased,while the relative abundances of 35d Romboutsia and 42d Cladomyces and Lactobacillus were significantly decreased（P<0.05）;（2）Bacillus subtilis treatment:（1）Compared with CIC.p group,significantly in-creased the 80d BW,43-80d and 1-80d ADG,43-80d ADFI（P<0.05）,significantly decreased 22-42d F/G（P<0.05）;serum TP and ALB level,TC concentration,HDL-C and TG concentration in 42d were significantly increased（P<0.05）,signifi-cantly decreased serum MDA concentration at 35d and 42d（P<0.05）.The bursae of Fabricius index was significantly increased at 35d（P<0.05）.The 35d jejunum and ileum scores and 42d jejunum scores were significantly decreased（P<0.05）;the concentration of 35d D-lactic acid and endotoxin were significantly decreased（P<0.05）;significantly increased 35d jejunum and ileum VH（P<0.05）;significantly down-regulated mRNA expression of Claudin-1 and Occludin in 35d jejunum,signif-icantly up-regulated mRNA expression of Mucin-2 in 35d jejunum（P<0.05）.The relative abundance of Allocladomyces on 35d in cecum was significantly increased,while the 35d relative abundance of Proteobacteria,Pseudomonas,Sectofilamentous bacteria and 42d Bacteroidetes in cecum was significantly decreased（P<0.05）;（2）Compared with C.p group,it significantly increased 1-80d death rate（P<0.05）;se-rum TC,LDL-C,HDL-C and TG concentration in 42d were significantly increased（P<0.05）.Duodenal scores on 35d and duodenal,jejunal and ileum scores on 42d were significantly decreased（P<0.05）.The CD of 35d jejunum was significantly increased,and the VH/CD of 35d jejunum was significantly decreased（P<0.05）.The mRNA expressions of Claudin-1 and IL-10 in 35d jejunum and Claudin-1,ZO-1,Mucin-2,IL-4 and IL-10 in 42d ileum were significantly down-regulated（P<0.05）.The rela-tive abundance of Acidobacteria and Myxomycetes in cecum at 35d was significantly increased（P<0.05）,significantly decreased the relative abundance of Coprofecalis at35d.Conclusion:1)By challenging yellow-feather broilers with coccidium and Clos-tridium perfringens or Clostridium perfringens alone,it was found that the intestinal damage was more serious under the combined infection of coccidium and Clostridium perfringens.2)Bacillus subtilis(QST713,1.0×10¹⁰CFU/g)could alleviate the degra-dation of production performance caused by changes in serum biochemical indexes,intestinal morphology and intestinal barrier function,as well as changes in cecal mi-croflora structure of broilers caused by challenge.