Dietary apidaecin Api-PR19 addition improves growth performance, intestinal health and modulating gut microbiota in broilers.

Objective:This study investigated the effects of Apidaecin Api-PR19 as feed additive on growth performance, intestinal health, and small intestinal microbiota of broilers. Methods:A total of 360 1-d-old Arbor Acres broilers were randomly assigned to 3 groups with 6 replicates including control group with basal diet (CON), antibiotic growth promotor group with basal plus 10 mg/kg colistin sulfate and 50mg/kg roxarsone (AGP), and antibacterial peptide group with basal diet plus 330 mg/kg Apidaecin Api-PR19 (ABP). The trial lasted 35 d. Results:Results showed that dietary Api-PR19 addition increased (p＜0.05) the average daily feed intake (ADFI), average daily gain (ADG) and decreased (p＜0.05) feed conversion ratio (FCR) during 1 to 21 d compared with the CON group. The digestibility of dry matter and crude protein were higher in AGP and ABP groups (p＜0.05) where greater trypsin activity was detected in duodenum (p＜0.05). The ratio of villus height to crypt depth (V/R) in duodenum and jejunum was increased at 35 d when broilers were given diets with ABP or AGP (p＜0.05). Besides, ABP treatments up-regulated (p＜0.05) the mRNA expression of EAAT3, GLUT2, ZO-1 and Claudin-1 in duodenum of broilers at 35 d of age. The results of immunohistochemistry showed that ABP treatment significantly increased (p＜0.05) duodenal sIgA content. In addition, 16S rRNA gene sequencing revealed that there were differences in the intestinal microbiota diversity and composition among three groups. Notably, the linear discriminant analysis effect size (LEfSe) showed that p_Firmicutes, g_Enterococcus, g_Carnobacterium, g_Kitasatospora and g_Acidaminococcus were dominant in ABP group. Redundancy analysis showed that these changes in gut microbiota in ABP group had correlation with growth performance, intestinal morphology, and content of sIgA. Conclusion:In general, these results indicated that dietary 330 mg/kg Apidaecin Api-PR19 supplementation promoted growth performance of broilers by improving intestinal development, nutrients absorption, immune function and modulating intestinal microbiota.