Effects of birth body weight and zinc source on growth, gut health and immune response in weaned piglets

Clara Negrini¹Diana Luise¹Federico Correa¹Sara Virdis¹Andrea Serra²Alessio Bonaldo¹Naiana Manzke³Alessandra Monteiro⁴Maurizio Mazzoni¹Paolo Trevisi^1*

• ¹University of Bologna, Bologna, Italy
• ²University of Pisa, Pisa, Tuscany, Italy
• ³Cargill (Netherlands), Amsterdam, Netherlands
• ⁴ANIMINE, Annecy, France

Zinc (Zn) is an essential trace element for piglets especially during the challenging post-weaning period. This study investigated the effects of two dietary Zn sources: zinc sulfate (ZnSO₄) and a porous zinc oxide (pZnO) used at European authorized dietary level on piglets of differing birth body weight (BBW): low (LBBW <1 kg) and normal (NBBW >1 kg). At weaning (25 days, d0), 64 piglets were assigned to 4 groups based on BBW and Zn source, to reach a total of 150 mg/kg of Zn. Body weight was monitored weekly until d21. On d9 and d21, 32 piglets were slaughtered for gut histology, immunohistochemistry, gene expression, blood markers, pH measurement, and microbiota and SCFA analysis. The NBBW had higher BW throughout the study (P<0.01), confirming BBW as a key factor influencing growth and physiological maturity. The pZnO group tended to have a higher average daily gain in the periods d0-d9 and d9-d14 (P<0.10). The pZnO reduced jejunum pH at d21(P=0.02). The interaction between diet and BBW influenced the nuclear factor kappa B subunit 2 (NFKB2) expression at d9 (P=0.03); with LBBW fed ZnSO₄ showing higher expression. At d21, the interaction between diet and BBW affected the villus height (P=0.05) and the absorptive mucosal surface (P=0.02) which were higher in the NBBW than LBBW fed ZnSO4, while no difference was observed between NBBW and LBBW fed the pZnO. Differences in microbiota beta diversity were associated with BBW (P=0.07 at d9; P=0.03 at d21) and taxa abundance varied with Zn source and BBW. Overall, the results demonstrate that the pZnO positively influenced gut health and performance in weaned piglets, particularly in LBBW. The differential response to Zn sources according to BBW suggests that tailored mineral strategies could help mitigate weaning stress in vulnerable piglets.