Development of a botanical-based feed additive to manage weaning stress in piglets

Weaning stress represents a persistent condition with long-term detrimental effects on piglets. It stimulates inflammation and oxidation, while enterotoxigenic Escherichia coli (ETEC) can overgrow and trigger diarrhea. Historically, weaning piglets’ health was supported by antibiotics (AB) and/or pharmacological zinc oxide (ZnO). However, their uncontrolled use caused resistance spread and environmental pollution. Botanicals represent a wide class of compounds that possess beneficial effects and qualify as novel tools to manage weaning stress in piglets. The aim of this thesis was to develop a new botanical-based feed additive to support piglets at weaning, as an alternative to antibiotics and ZnO. Microbiology and cell culture experiments allowed to find selected botanicals that were efficacious in controlling ETEC growth and virulence, and supporting intestinal cells health during ETEC infections. The optimized combination of botanicals (BOT) was further validated in vitro: in enterocytes and hepatocytes, BOT displayed a robust activity against acute and chronic stress triggered by inflammatory and ETEC challenges. Its mechanism of action involved cellular integrity protection, inflammatory response reduction, oxidative status enhancement, and susceptibility to ETEC decrease. BOT was then supplemented in the diet of weaning piglets and its beneficial effects were investigated in vivo. Firstly, BOT exhibited a strong action against E. coli lipopolysaccharide by improving intestinal integrity and regulating liver inflammatory and oxidative status, allowing better growth in challenged piglets. Secondly, during an ETEC challenge trial, BOT proved able to control ETEC virulence, thus enhancing intestinal integrity and inflammatory status, and allowing better growth patterns in infected piglets. Finally, in a clean feeding trial, BOT maintained good performance and considerably reduced medical treatments compared to ZnO. In conclusion, BOT represents a novel feed additive to support growth and counteract stress in weaning piglets. By influencing several stages of the host-pathogen interaction, BOT represents a valid alternative to pharmacological ZnO.