Effect of Bacillus Probiotics on Growth Performance, Diarrhea Incidence, Nutrient Digestibility, and Intestinal Health of Weaned Piglets

Weaned piglets have a fragile gastrointestinal tract and immature digestive function. Supplementation of Bacillus can enhance intestinal barrier function and improve nutrient digestion and absorption efficiency. It is an important nutritional regulation method to alleviate weaning stress, reduce the incidence of diarrhea and promote growth performance. This experiment was conducted to investigate the effects of <i>Bacillus subtilis</i>, <i>Bacillus pumilus</i> and their combination on growth performance, diarrhea incidence, nutrient apparent digestibility, intestinal morphology and barrier function of weaned piglets. A total of 128 weaned piglets weighing 6.68 kg (±0.35 kg) were selected, divided into 4 treatment groups, and fed with a basal diet (CTR), a <i>Bacillus subtilis</i> (BS1), a <i>Bacillus pumilus</i> (BS2) and a <i>Bacillus subtilis</i> + <i>Bacillus pumilus</i> (BS1 + BS2) for 42 days. Each group had 8 replicates with 4 piglets per replicate. One piglet was selected from each replicate and euthanized to collect intestinal samples. The results showed that compared with the CTR group, the BS1 + BS2 group significantly increased the average daily gain (ADG) of weaned piglets on days 0-14 (<i>p</i> < 0.05), and the BS2 group significantly increased the ADG on days 0-42 (<i>p</i> < 0.05). Compared with the CTR group, the BS1 + BS2 group significantly reduced the full-time diarrhea rate (<i>p</i> < 0.05), and weaned piglets of the BS2 group significantly reduced the incidence of diarrhea on days 0-14, 15-28, and 0-42 of the study, in comparison to the control (<i>p</i> < 0.05). Compared with the CTR group, the piglets in the BS1 + BS2 group significantly decreased the serum tumor necrosis factor-α (TNF-α) content on day 21 (<i>p</i> < 0.05), and the BS1, BS2, and BS1 + BS2 groups significantly decreased the serum TNF-α content on day 42 (<i>p</i> < 0.05). Compared with the CTR group, the BS1 + BS2 group significantly reduced the expression of Interleukin-8 (<i>IL-8</i>) mRNA in the ileum (<i>p</i> < 0.05). The BS1, BS2, and BS1 + BS2 groups significantly reduced the expression of <i>TNF-α</i> mRNA in the ileum, <i>IL-8</i> mRNA in the jejunum, and <i>TNF-α</i> mRNA in the jejunum (<i>p</i> < 0.05). In addition, compared with the CTR group, the BS2 and BS1 + BS2 groups significantly increased <i>Claudin-1</i> mRNA expression in the jejunum (<i>p</i> < 0.05). Compared with the CTR group, the BS1 and BS2 groups significantly increased <i>Occludin</i> mRNA expression in the jejunum (<i>p</i> < 0.05). In summary, dietary supplementation with <i>Bacillus</i>-based probiotics can significantly improve growth performance in weaned piglets, reduce diarrhea incidence, alleviate inflammation, and enhance intestinal barrier function.