Effects of yeast fermentate supplementation on cecal microbiome, plasma biochemistry and ileal histomorphology in stressed broiler chickens

Heat stress, a common stressor in commercial poultry production, negatively affects growth and intestinal function of broiler chickens. Two experiments were conducted to evaluate the effects of a Saccharomyces cerevisiae-derived yeast fermentation product on cecal microbiome and indicators of intestinal barrier function in stressed broiler chickens. Yeast fermentate (YF) was added to the feed (1.25 kg/t) or drinking water (1.60 mL/L) for the duration of each experiment. In Exp. 1, 1-D-old male broiler chickens (N = 300 birds/treatment) were assigned to 1 of 3 treatments: stressed control (CS), stressed + YF in the feed (XS), and stressed + YF in the drinking water (AS). All birds were reared on re-used litter (d 0 to 42) and spray-vaccinated for coccidiosis (d 0). On d 18, all birds were spray-vaccinated for Newcastle/Bronchitis, then exposed to a 12 h concurrent heat stress and feed and water withdrawal. Cecal microbiome did not differ in composition or diversity between or within treatments on d 42. In Exp. 2, 1-D-old male broiler chickens (N = 40 birds/treatment) were reared to 43 d of age. Treatments included CS, XS, AS, non-stressed control (CN), non-stressed + YF in the feed (XN), and non-stressed + YF in the drinking water (AN). Stressed treatments were exposed to cyclic heat stress d 28 to 43 for 12 h/d. Blood samples collected on d 42 were used to analyze plasma chemistry, interleukin(IL)-1 alpha, IL-8, and alpha-1 -acid glycoprotein (alpha(1)-AGP); ileum samples collected on d 43 were used to assess histomorphology. Heat stress increased plasma creatine kinase (P < 0.001), uric acid (p < 0.001), sodium/potassium ratio (P < 0.001), and IL-1 alpha (P < 0.001), but decreased alkaline phosphatase (P = 0.04), potassium (P < 0.001), IL-8 (P < 0.001), and alpha(1)-AGP (P = 0.048). Plasma glutamate dehydrogenase was higher in birds fed the control diet or YF in the feed (P < 0.001) compared to birds supplemented with YF in the drinking water. Heat stress decreased villus height (P < 0.001) and crypt depth (P < 0.001), and increased villus/crypt ratio (P < 0.001) and goblet cell density (P < 0.001). Supplementing YF in the drinking water increased villus height (P < 0.001) and crypt depth (P = 0.036) compared to supplementing YF in the feed. Adding YF to the drinking water may be an effective method to mitigate heat-stress induced changes in villus height and crypt depth during cyclic heat stress.