Effects of purple corn anthocyanin on slaughter performance, immune function, the caecal microbiota and the transcriptome in chickens

Poultry are susceptible to oxidative stress, which decreases immune function and negatively affects production performance under highly intensive feeding conditions. Moreover, anthocyanins can alleviate oxidative stress and improve immune functions in chickens. This study aimed to elucidate the effects of purple corn anthocyanin extract (PCE) on slaughter performance, immune function, the caecal microbiota and the transcriptome in chickens. A total of 180 female chickens were randomly divided into two groups, with one receiving a basal diet (CON) and one receiving a treatment (PCE) supplemented with 360 mg/kg PCE according to a completely randomized design. The results indicated that the levels of plasma immunoglobulin A, immunoglobulin G, immunoglobulin M, complement 3, and complement 4 in the PCE treatment group were greater (P < 0.05) than those in the CON group. The slaughter performance and caecal short-chain fatty acid parameters did not differ (P > 0.05) between the PCE and CON groups. The inclusion of PCE significantly increased (P < 0.05) the bursa of Fabricius/live weight value compared with those of the CON. Chickens receiving PCE had significantly (P < 0.05) increased relative abundances of norank_f_Muribaculaceae, Anaerofilum, Shuttleworthia, Brachyspira, and Tuzzerella but significantly decreased (P < 0.05) relative abundances of unclassified_f__Rikenellaceae, Oscillospira, norank_f__Barnesiellaceae, norank_f__Christensenellaceae, and Candidatus_Soleaferrea. A total of 2,846 differentially expressed genes (DEGs; P < 0.05), which consisted of 1,140 upregulated genes and 1,706 downregulated genes, were identified. Among them, 201 genes were annotated to the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes database for immune-related genes. Protein-protein interaction network analysis revealed that DEGs associated with the joining chain of multimeric IgA and IgM were significantly upregulated immune-related genes, and those associated with forkhead box P1, cathelicidin 1, cathelicidin 2, and cathelicidin 3 were significantly downregulated immune-related genes in chickens. The findings demonstrated that dietary supplementation with PCE has the potential to improve plasma immunoglobulin, immune organ, caecal potentially beneficial bacteria levels and immune-related gene expressions, which can increase the immune function of chickens.