Effects of encapsulated thymol and carvacrol mixture on growth performance, antioxidant capacity, immune function and intestinal health of broilers

This study evaluated the effect of encapsulated thymol and carvacrol mixture (ETCM) on the growth performance, antioxidant capacity, immune function and intestinal health of broilers. In total, 400 one-day-old male Arbour Acres broilers were randomly allocated to two groups with eight replicates of 25 birds each and fed a basal diet (control) or a basal diet supplemented with 150 mg/kg ETCM. The trial lasted 42 days. ETCM supplementation significantly increased (p < .05) average daily gain at d 22-42 and the organ indices of the spleen, pancreas and bursa of Fabricius at d 42. Regarding the serum antioxidant indices, ETCM supplementation significantly increased (p < .05) glutathione peroxidase (GSH-Px) and superoxide dismutase activities and decreased (p < .05) the malondialdehyde content at d 21 and 42. Furthermore, it significantly increased the villus height and villus height-to-crypt depth ratio in the jejunum at d 21 and the ileum at d 42. ETCM supplementation also up-regulated (p < .05) the intestinal mRNA levels of nuclear factor erythroid-2 related factor 2 (Nrf2), GSH-Px, occludin and zonula occludens-1 in the jejunal mucosa, while down-regulated (p < .05) the mRNA levels of nuclear factor kappa B (NF-kappa B), interleukin 1 beta, and tumour necrosis factor-alpha. Thus, ETCM positively impacts the growth performance, antioxidant capacity and immune function of broilers. ETCM can also improve intestinal health which may be partially related to the activation of the Nrf2 signalling pathway and the suppression of the NF-kappa B signalling pathway.