Alternatives to antibiotics in pig production: looking through the lens of immunophysiology

Abstract

In the livestock production system, the evolution of porcine gut microecology is consistent with the idea of "The Hygiene Hypothesis" in humans. I.e., improved hygiene conditions, reduced exposure to environmental microorganisms in early life, and frequent use of antimicrobial drugs drive immune dysregulation. Meanwhile, the overuse of antibiotics as feed additives for infectious disease prevention and animal growth induces antimicrobial resistance genes in pathogens and spreads related environmental pollutants. It justifies our attempt to review alternatives to antibiotics that can support optimal growth and improve the immunophysiological state of pigs. In the current review, we first described porcine mucosal immunity, followed by discussions of gut microbiota dynamics during the critical weaning period and the impacts brought by antibiotics usage. Evidence of in-feed additives with immuno-modulatory properties highlighting probiotics, prebiotics, and phytobiotics and their cellular and molecular networking are summarized and reviewed. It may provide insights into the immune regulatory mechanisms of antibiotic alternatives and open new avenues for health management in pig production.

Keywords: Antibiotics; Gut-associated lymphoid tissues; Phytobiotics; Prebiotics; Probiotics; The Hygiene Hypothesis.

Fig. 1

The organization of Peyer’s patches (PPs). (a) Schematic representation of PPs and the immune cell distribution. (b) Immunohistochemical staining of rodent ileum PPs with anti-GL7 (cyan) for germinal center and anti-B220 (magenta). (c) Histological image of porcine ileum PPs with H&E staining. Scale bars = 100 μm. FAE, follicular associated epithelium; IEL, intraepithelial lymphocyte; HEV, high endothelial venules

Fig. 2

Schematic illustration of the regulatory effects of probiotics in swine