Dietary supplementary with soya saponins alleviates the poor intestinal health of broilers challenged with coccidia via reshaping the structure of the intestinal microbiota

Soya saponins (SS) have the ability to improve the intestinal microbiota and enhance intestinal immune function. While, there are few reports on their application in broiler production. The present study was designed to investigate effects of dietary supplementary with SS on the intestinal health of birds challenged with coccidia (CC). 180 male and healthy Cobb 500 broiler chickens with unifrom body weight were randomly divided into 3 treatment groups, those groups were named as the control group (CTR), the coccidia challenged group (CC), and the SS treated group challenged with CC (SS+CC). There were 6 replicates in each group, and 10 birds in each replicate. Birds in the CTR and CC group were fed with the basic diet, and birds in the SS+CC group were fed with the basic diet supplemented with 200 mg/kg SS. The animal trial lasted for 21 days, on day 10 and 12, birds in the CC and SS+CC group were challenged with CC, and birds in the CTR group were treated with normal saline, samples were harvested on day 14, and the growth performance from day 1 to day 10 as well as from day 1 to day 21 were recorded. Outcomes showed that the body weight (BW), average daily weight gain (ADG) and average daily feed intake (ADFI) were descended, and the feed conversion ratio (FCR) was elevated with CC challenged (P < 0.05). The villi height (VH) and the ratio of VH to crypt depth (CD) in jejunum and ileum were decreased with CC challenged, as well as the levels of ileal secretory immunoglobulin A (sIgA) and acetic acid in the ileal chyme (P < 0.05). Additionally, the mRNA level of ileal occludin was down-regulated, the transcriptional levels of ileal IL-8, interferon-γ (IFN-γ), cysteine-dependent aspartate-specific protease-1 (Caspase-1), and induced NO synthase (i-NOS) were up-regulated with CC challenged (P < 0.05). Dietary supplementary with SS tended to improve the FCR from day 1 to day 10 (P = 0.06), and was able to alleviated the above-mentioned negative effects induced by CC. Interestingly, dietary supplementary with SS contributed to reshaping the structure of the intestinal microbiota, specifically, reshaping the abnormal changes in the abundance of Lactobacillus and Romboutsia in the ileal chyme challenged with CC (P < 0.05). It was worth mentioning that the relative abundance of Lactobacillus was positively correlated with the levels of short-chain fatty acids in the ileal chyme, and it of Romboutsia was positively correlated with the mRNA levels of ileal IL-8, IFN-γ, Caspase-1, and i-NOS (P < 0.05). In conclusion, dietary supplementary with SS alleviated the poor intestinal health of broilers caused by CC via reshaping the structure of the intestinal microbiota.