Evaluation of Effectiveness and Safety of Microcin C7 in Weaned Piglets

SIMPLE SUMMARY: The bactericidal mechanisms and immunomodulatory effects of Microcin C7 (C7) have been confirmed by many studies. However, most studies were performed in vitro and need to be substantiated with in vivo data. We showed that C7 supplementation can improve growth performance, reduce diarrhea rate, and that the diarrhea-alleviating effect of C7 may be related to its selective regulation of specific microbial taxa. C7 improved the intestinal morphology of the duodenum and ileum and enhanced diet digestibility. The recommended C7 dosage is 250–500 mg/kg. Supplementation with 5000 mg/kg had no adverse effect on all indices; thus, this is a safe threshold for C7 usage in clinical practice. Overall, these data indicate that C7 is safe and effective for use as a potential alternative to antibiotic growth promoters in weaned piglets. ABSTRACT: The effects and safety of dietary supplementation with Microcin C7 (C7) were evaluated in 216 weaned piglets. The pigs were given a control corn–soybean meal basal diet or C7 diet (control diet supplemented with 250, 500, 750, 1000, or 5000 mg C7/kg diets). Compared with the control group, the 500 mg/kg C7 supplementation group had better intestinal morphological indicators (p < 0.05), which may help maintain intestinal epithelial function and increase the growth performance (p < 0.05) and apparent total tract digestibility (p < 0.05). The diarrhea indexes of the 250, 500, and 750 mg/kg groups were significantly lower than that of the control group at 0–28 d (p < 0.05), and the 500 mg/kg group had the lowest diarrhea indexes (linear and quadratic, p < 0.05). A comprehensive analysis showed that microbial structure was significantly correlated with the degree of diarrhea, and the diarrhea-alleviating effect of C7 may be related to its selective regulation of specific microbial taxa. The 250 and 500 mg/kg C7 supplementation also significantly improved several immune indices of piglets (p < 0.05). Compared with the control diet, 5000 mg/kg C7 supplementation had no significant adverse effect on all parameters. Overall, the 250–500 mg/kg dose had the best effect, and the highest dose (5000 mg/kg) posed no toxicity risk. Therefore, C7 appears safe for use as an alternative to antibiotic growth promoters in weaned piglets.