Effects of dietary supplementation with periplaneta americana-derived antimicrobial peptides on (PA-AMPs) growth performance, immune function, and gut health in yellow-feathered broilers

This study aimed to comprehensively investigate the effects of American cockroach antimicrobial peptide (PA-AMPs) on yellow-feathered broilers. Three hundred one-day-old yellow-feathered broilers were randomly divided into five groups: the control group (CON) fed a basal diet, three PA-AMPs treatment groups with 100 mg/kg, 200 mg/kg, and 300 mg/kg PA-AMPs added to the basal diet respectively, and the ARY group with 20 mg/kg chlortetracycline in the basal diet. Each group had six replicates of 10 chickens each, and the experiment lasted for 70 days.The results showed that adding different levels of PA-AMPs to the basal diet significantly increased the body weight and average daily gain (ADG) of yellow-feathered broilers aged 43 - 70 days (P<0.05), with the 200 mg/kg PA-AMPs group having the best growth-promoting effect. PA-AMPs also significantly improved meat quality parameters such as shear force, pH value at 0.75 h post-slaughter, meat color, and muscle fat content compared with the CON group (P <0.05).The total antioxidant capacity in the 200 mg/kg PA-AMPs and ARY groups increased significantly, while malondialdehyde decreased significantly (P <0.05). In terms of blood biochemical indices, the levels of TP, AST, and ALT in the 200 mg/kg PA-AMPs and ARY groups were significantly higher than those in the CON group (P <0.05), with no significant difference between the two groups (P >0.05). Immunoglobulin contents in the 200 mg/kg PA-AMPs group were significantly higher than those in the CON group (P <0.05) and similar to those in the ARY group (P >0.05). Inflammatory cytokines in all experimental groups decreased significantly, and IL-6 in the 200 mg/kg and 300 mg/kg PA-AMPs groups and the ARY group also decreased significantly (P <0.05). Regarding intestinal barrier function, dietary supplementation with 200 mg/kg PA-AMPs significantly upregulated mRNA expression of tight junction proteins (Occludin, Claudin-1, and ZO-1) in the duodenum, jejunum, and ileum (P < 0.05), while markedly downregulating the expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) (P < 0.05).Regarding gut microbiota, dietary supplementation with 200 mg/kg PA-AMPs significantly reduced the relative abundance of Desulfobacterota, Spirochaetota, and Oscillospiraceae in the cecum of broilers (P < 0.05). Therefore, it is recommended to add 200 mg/kg PA-AMPs to the basal diet of yellow-feathered broilers.