Today, several strategies are being used to decrease the serious effects of antibiotics abuse on broilers industry and public health, among which synbiotics are one of the most promising antibiotic alternative. This study was undertaken to assess the effects of synbiotics, which composed of probiotics (Bacillus subtilis) and prebiotics (xylooligosaccharide and mannanoligosaccharide), on growth performance, intestinal morphology, sIgA content and antioxidant parameters of broilers. Four hundred and fifty one-day-old commercial Cobb48 broilers were assigned to five treatments consisting of six replicates of 15 birds each pen. Five dietary treatments include basal diets (control), basal diets plus antibiotics (4 mg/kg Xanthomycin), basal diets plus 1 g of probiotics B. subtilis product/kg of diets (4 × 10 cfu/kg), basal diets plus 150 mg/kg xylooligosaccharide (35%) and 1 g/kg mannanoligosaccharide (75%), and basal diets plus synbiotics (1 g of probiotics B. subtilis product/kg of diets (4 × 10 cfu/kg), 150 mg/kg xylooligosaccharide (35%) and 1 g/kg mannanoligosaccharide (75%). The results demonstrated that on 21 and 42 days, dietary supplementation of the synbiotics significantly increased daily weight gain (p < 0.05), feed efficiency (p < 0.05), the villus height and villus:crypt ratio in the duodenum, jejunum and ileum (p < 0.05), as well as intestinal mucosa sIgA content (p < 0.05), serum T-SOD activity (p < 0.05) and lysozyme content (p < 0.05), comparing with control group. In conclusion, synbiotics (B. subtilis and xylooligosaccharide and mannanoligosaccharide) is one of the safe and ideal dietary supplementations to increase broilers' growth performance by improving small intestinal morphology, sIgA content and antioxidant capabilities.

In recent decades, probiotics have attracted widespread attention and their application in healthcare and animal husbandry has been promising. Among many probiotics, Bacillus coagulans (B. coagulans) has become a key player in the field of probiotics in recent years. It has been demonstrated to be involved in regulating the balance of the intestinal microbiota, promoting metabolism and utilization of nutrients, improving immunity, and more importantly, it also has good industrial properties such as high temperature resistance, acid resistance, bile resistance, and the like. This review highlights the effects of B. coagulans in animal husbandry and its underlying mechanisms.

Along with banning antibiotics, necrotic enteritis (NE), especially subclinical enteritis (SNE), poses a significant threat to the chicken industry; however, probiotics are a potentially promising intervention. We aimed to investigate the beneficial effects of Bacillus subtilis DSM29784 (BS) on the treatment of Clostridium perfringens (CP)-induced SNE in broilers. A total of 360 1-day-old broiler chicks were divided into three treatment groups, namely control (Ctr), SNE, and BS treatment (BST) groups, all of which were fed with a basal died for 21days, and then from day 22 onward, only the BST group had a BS supplemented diet (1×109 colony-forming units BS/kg). On day 15, all chicks, except the Ctr group, were challenged with a 20-fold dose coccidiosis vaccine and 1ml CP (2×108) on days 18–21 for SNE induction. Beneficial effects were observed on growth performance in BST compared to SNE broilers. BST treatment alleviated intestinal lesions and increased the villus height/crypt depth ratio. Further, BST broilers showed increased maltase activity in the duodenum compared with SNE chicks, and a significantly decreased caspase-3 protein expression in the jejunum mucosa. Moreover, an increased abundance of Ruminococcaceae and Bifidobacterium beneficial gut bacteria and an altered gut metabolome were observed. Taken together, we demonstrate that the manipulation of microbial gut composition using probiotics may be a promising prevention strategy for SNE by improving the composition and metabolism of the intestinal microbiota, intestinal structure, and reducing inflammation and apoptosis. Hence, BS potentially has active ingredients that may be used as antibiotic substitutes and effectively reduces the economic losses caused by SNE. The findings of this study provide a scientific foundation for BS application in broiler feed in the future.