Antimicrobial Peptides Improved Growth Performance by Intervening Ileac Microorganisms and Metabolites in Holstein...

The use of antibiotics as feed additives has promoted the emergence of antimicrobial resistance, thereby increasing the morbidity and mortality associated with infections that were previously treatable. Antimicrobial peptides (AMP) have appeared as a promising strategy in replacing antibiotics in ruminant production. However, there are few reports on the effects of AMP on the ileal function, microorganisms and metabolites in Holstein steers. In this study, Eighteen Holstein steers were split randomly into two groups (n = 9). The control group (CON) was fed a basic diet, and antimicrobial peptide group (AMP) was fed basic diet supplemented with 8 g/(d·head) of AMP for 270 days. AMP significantly improved ileac volatile fatty acids (VFA), such as propionate (P ≤ 0.05), and the ileal absorptive surface area - villus height (VH, P ≤ 0.05). Thereby enhanced growth performance of steers (P ≤ 0.05), including final body weight (FBW), average daily gain (ADG) and carcass weight (CW). And then, we reported and supplemented the profiles of the ileac microorganisms and metabolites of Holstein cattle using metagenomics and metabolomics. AMP reduced both virus abundance and Clostridium growth, and increased the microbial abundance in ileum of steers; Turicibacter sanguinis and Clostridium perfringens were dominant microorganisms in AMP and CON group, respectively. LPE, Hyodeoxycholic acid and Hyodeoxycholic acid effected the growth and health of steers. KEGG analysis revealed that AMP improved growth by upregulating ileac amino acid and carbohydrate metabolism. Spearman analysis indicates key microorganisms and metabolites interacted with each other and promoted the growth and health of steers. These findings provide essential insights into the molecular mechanisms in effect of AMP on ileac microorganisms and metabolites of steers, which suggested its potential application as a dietary additive to improved growth and health in steers.