Effects of Prebiotics and Probiotics on Gut Health, Immunity, and Growth of Weanling Pigs

As antibiotic alternatives, prebiotics and probiotics have been recently investigated to modulate intestinal bacteria, promote gut barrier functions and immunity, and benefit health and growth in pigs. However, the prebiotic effects of different sources vary; and, how to determine a viable probiotic strain remains unclear. We conducted 2 nursery experiments to evaluate the prebiotic effects related to the alteration of microbial community; and subsequently, a potential probiotic species was selected and examined for health promoting effects in combination with the prebiotic. In Exp. 1, 64 weanling pigs were fed 1 of the 4 dietary treatments: control, chicory, mannan-oligosaccharides (MOS), and chitosan for 4 weeks. With the exception of a subtle decrease in G:F by feeding MOS, dietary prebiotics did not affect growth performance or serum IgA in weanling pigs. Feeding MOS showed prebiotic effects by increasing fecal VFA and the abundances of Lactobacillaceae and Streptococcaceae. The abundance of Lactobacillus mucosae (LM) was positively correlated with serum IgA, indicating a potential probiotic effect. In Exp. 2, to determine the prebiotic, probiotic, and synergistic effects of MOS and LM, 96 weanling pigs were allotted in a 2 × 2 factorial arrangement of treatments, followed by an Escherichia coli Lipopolysaccharides (LPS) challenge. Feeding MOS increased circulating IgG from 2 weeks post-weaning and showed a carry-over effect after removal of treatments, which may protect the pigs from acute inflammation due to LPS-challenge. Pigs fed the LM alone indicated improved gut barrier functions by increased secretory IgA and decreased ileal crypt depth, resulting in enhanced feed efficiency during the LPS-challenge. However, these beneficial effects diminished after the LM treatment was removed. Unexpectedly, we did not observe the synergistic effects of MOS and LM. In addition, a third experiment was conducted to determine the variations of bacterial community in different locations of gastrointestinal tract and dietary treatments. In conclusion, this dissertation demonstrated a model in weanling pigs to study the potential prebiotic and probiotic products. It also elucidated the effects of feeding MOS and LM on gut health, immunity, and growth of weanling pigs