Growth performance, nutrient digestibility, intestinal morphology, cecal mucosal cytokines and serum antioxidant responses of broiler chickens to dietary enzymatically treated yeast and coccidia challenge

BACKGROUND: There is a growing search for natural feed additives to alleviate the deleterious effects of coccidia infection in poultry production. This study aimed to investigate the effect of enzymatically treated yeast (ETY) on the growth performance, nutrient digestibility, intestinal morphology, antioxidative status, and cecal mucosa cytokines of coccidia-challenged broiler chickens. METHODS: From d 1 to 14 post hatching, 480 broiler chickens were allocated to 3 corn-soybean meal-based experimental diets with increasing concentrations of ETY (0, 1, or 2 g/kg). The experiment was designed as a randomized complete block design with body weight (BW) used as a blocking factor. On d 14 post hatching, the birds were re-randomized within each of the 3 experimental diets. Each of the 3 diet groups was split into a challenge or no-challenge group. This resulted in a 3 × 2 factorial arrangement of treatments. The coccidia challenge was administered on d 15 by an oral gavage. RESULTS: Dietary ETY improved (P < 0.05) the G:F of birds on d 21 regardless of the challenge state and linearly increased (P < 0.01) the apparent ileal digestibility of dry matter (DM), nitrogen, and gross energy (GE). The coccidia challenge decreased (P < 0.05) BW gain and feed intake of broiler chickens and reduced (P < 0.01) the total tract retention of DM, GE, and nitrogen. The coccidia challenge increased (P < 0.01) the mRNA gene expression of TNFα, IL-1β, IL-10, and IL-6 in the cecal mucosa. There was a tendency (P = 0.08) for ETY to linearly reduce IL-1β expression. Additionally, ETY supplementation increased (P < 0.05) the gene expression of OCLN. Serum catalase increased (P < 0.05) with dietary ETY in broiler chickens on d 21. Dietary ETY linearly increased (P < 0.05) the ileal villus height to crypt depth ratio, and ileal goblet cell density in broiler chickens. The ileal and excreta oocyst counts decreased (P < 0.01) with increasing supplementation of dietary ETY in coccidia-challenged broiler chickens on d 21. CONCLUSIONS: Dietary ETY enhanced nutrient utilization and augmented intestinal development in broiler chickens. However, dietary ETY did not completely attenuate the adverse effects of a coccidia challenge in broiler chickens. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40104-023-00846-z.