摘要Probiotics can improve animal growth performance and intestinal health.Bacillus species,Lactobacillus species,Bifidobacterium species,yeast etc.are the common types of probiotics.However,understanding the effects of probiotics on the immune status and gut microbiota of weaning piglets and how the probiotics exert their impact are still limited.This study aimed to investigate the effects of Bacillus amyloliquefaciens 40(BA40)on the performance,immune status and gut microbiota of piglets.A total of 12 litters of newborn piglets were randomly divided into 3 groups.Piglets in control group were orally dosed with phosphate buffered saline;BA40 group and probiotics group were orally gavaged with resuspension BA40 and a probiotics product,respectively.The results showed that BA40 treatment significantly decreased(P＜0.05)the diarrhea incidence(from d 5 to 40),diamine oxidase,D-lactate,interleukin(IL)-1β and interferon-γconcentrations compared with control group and probiotics group.Meanwhile BA40 dramatically increased the total antioxidant capacity,IL-10 and secretory immunoglobulin-A concentrations in contrast to control group.For the microbial composition,BA40 modulated the microbiota by improving the abundance of Bacteroides,Phascolarctobacterium(producing short-chain fatty acids)and Desulfovibrio and reducing the proliferation of pathogens(Streptococcus,Tyzzerella,Vellionella and paraeggerthella).Mean-while,a metabolic function prediction explained that carbohydrate metabolism and amino acid meta-bolism enriched in BA40 group in contrast to control group and probiotics group.For correlation analysis,the results demonstrated that BA40-enriched Phascolarctobacterium and Desulfovibrio provide insights into strategies for elevating the health status and performance of weaned piglets.Altogether,BA40 exerted stronger ability in decreasing diarrhea incidence and improved antioxidant activity,gut barrier function and immune status of piglets than the other treatments.Our study provided the experimental and theoretical basis for the application of BA40 in pig production.