Mechanically activated zinc oxide enhances growth performance and protects against diarrhea with potentially...

High pharmacological doses of zinc oxide (ZnO) are widely used to control post-weaning diarrhea, but environmental pollution and potential adverse effects necessitate the search for effective low-dose alternatives. This study aimed to investigate the effects of dietary level of mechanically activated zinc oxide on growth performance and diarrhea in weaned piglets. A total of 1152 healthy weaned piglets (6.72 ± 0.63 kg) at 21 d of age were randomly assigned to six treatment groups with six replicates of 32 pigs per pen. Piglets received either a basal diet (BD), the BD supplemented with 100, 200, 400, or 600 mg Zn/kg mechanically activated zinc oxide (100 Zn, 200 Zn, 400 Zn, and 600 Zn), or the BD supplemented with 1600 mg Zn/kg conventional ZnO (1600 Zn) over a 28-d feeding period. Compared with the BD group, dietary 400 Zn supplementation significantly increased average daily gain during d 1 to 14, and decreased the feed/gain ratio during d 1 to 14 and d 1 to 28 (P < 0.05). Additionally, dietary 400 Zn supplementation consistently decreased the diarrhea rate regardless of the experimental period (P = 0.001). Notably, these effects are comparable to those observed with 1600 Zn treatment. Moreover, compared to 1600 Zn group, 400 or 600 Zn supplementation significantly reduced interleukin-6 (IL-6) content and diamine oxidase (DAO) activity, as well as significantly increased superoxide dismutase (SOD) activity (P < 0.05) in serum at d 28. Conversely, no significant differences were observed in serum malondialdehyde (MDA) and interleukin-1β (IL-1β) concentrations between the 400 or 600 Zn groups and the 1600 Zn group throughout the experimental period (P > 0.05). Further gut microbiome and serum metabolomic analysis found that the abundances of Lactobacillus, Ligilactobacillus, and Roseburia increased and tryptophan metabolism pathway was enriched by 400 Zn supplementation. Furthermore, the differential metabolites involved in tryptophan metabolism significantly correlated with most of differential genera. In conclusion, dietary supplementation with mechanically activated zinc oxide at 400 mg Zn/kg could exerted a certain positive effect on the growth performance of weaned piglets, which was comparable to or even superior to that of 1600 mg Zn/kg ZnO, indicating that mechanically activated zinc oxide could serve as an effective alternative to high-dose ZnO used in weaned piglets.