Effect of Supplementation with Bee Antibacterial Peptides and Turmeric Essential Oil on Microbial Enumeration and Intestinal Integrity-Related Genes, Immunity, and Performance in Heat-Stressed Broilers.

Heat stress (HS) is one of the many challenges facing the poultry industry. Many effective strategies reduce the harmful effects of HS on birds, the most important of which are feed additives due to their many beneficial properties. The present study investigated the effects of dietary supplementation with antibacterial peptides (melittin [MEL]) and turmeric essential oil on growth performance, cecum microbial content, immunity, and gene expression in heat-stressed broilers. The first experiment, a completely randomized design, used three levels of MEL (50, 100, and 150 mg kg -1), with five replicates of 10 chicks each. In the second experiment, a total of 600 one-day-old chicks were completely randomly distributed into five experimental groups. The five experimental groups included the following: the first group was fed a basal diet without feed additives or exposed to HS (the control group), the second group was fed a basal diet and exposed to HS without feed additives (COHS), while the other groups were exposed to HS and adding turmeric essential oil (TEO, 200 mg kg-1), melittin (MEL, 150 mg kg-1), and their mixture (MTC). Results of the first experiment indicated that body weight gain (1 to 28 days) increased linearly, while the feed conversion ratio decreased linearly (P < 0.05) with increasing MEL supplementation. In the second experiment, results indicated that dietary supplementation with MTC improved broilers' growth performance through lowering the feed conversion ratio and raising the body weight gain, and crude protein digestibility (P < 0.05). It also enhanced carcass characteristics (P < 0.05) by increasing carcass yield, breast meat, and thigh meat, while decreasing abdominal fat. Supplementing MTC boosted the immuno-antioxidant status by increasing IgA, IL-10, and superoxide dismutase levels (P < 0.05) and decreasing IL-6 and MDA levels. Additionally, MTC maintained intestinal integrity by increasing intestinal ZO-1 and MUC-2 gene expression (P < 0.05) and increasing Lactobacillus count. In conclusion, adding MTC mitigated the negative effects of HS by boosting growth performance and immune-antioxidant status, modifying intestinal microbiota, and up-regulating ZO-1 and MUC-2 gene expression in broiler chickens.