Effect of Yeast Fermentate Supplementation on Intestinal Health and Plasma Biochemistry in Heat-Stressed Pekin Ducks.
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One experiment was conducted to determine the effects of supplementing Saccharomyces cerevisiae-derived yeast fermentate (Diamond V Mills, Cedar Rapids, IA, USA) in the feed (XPC; 1.25 kg/metric ton feed, days 0-35) or drinking water (AviCare; 160 mL/100 L, days 0-35) on plasma biochemical and immune parameters, as well as ileal histomorphology of mixed-sex Pekin ducks grown to 35 d and exposed to cyclic heat stress (8 h/d) or thermoneutral environment (days 21-35). On the day of hatching, 144 straight run White Pekin ducks were randomly assigned to one of six treatments: stressed control (CS), stressed + XPC (XS), stressed + AviCare (AS), non-stressed control (CN), non-stressed + XPC (XN), and non-stressed + AviCare (AN). On day 33, blood samples were collected from 12 birds/treatment to assess plasma chemistry, packed cell volume, and plasma levels of interleukin (IL)-1, IL-8, and 1-acid glycoprotein (1-AGP). On day 34, ileum sections were collected from 12 birds/treatment to assess goblet cell density, villus length, crypt depth, and villus/crypt ratio from 6 villi per sample. Plasma phosphorus was influenced by diet (p < 0.001) and heat-diet interaction (p = 0.003), and was higher in XS than XN, and higher in AS than AN. Heat stress increased plasma glutamate dehydrogenase (GLDH) (p = 0.008). Uric acid was increased by adding yeast fermentate to the feed or drinking water (p = 0.002), but was not influenced by heat (p > 0.05). The heat-diet interaction affected plasma IL-1 (p = 0.021) and sodium (p = 0.046). Heat stress reduced villus length (p < 0.001), villus/crypt ratio (p < 0.001), and goblet cell density (p < 0.001), but did not affect crypt depth (p > 0.05). Both XPC and AviCare increased villus length (p < 0.001) and villus/crypt ratio (p < 0.001), and decreased crypt depth (p < 0.001), but did not affect goblet cell density (p > 0.05). Although adding yeast fermentate to the feed or drinking water does not appear to alleviate the effects of heat stress on goblet cell density, both routes of administration improved other measures of villus morphology and affected amino acid metabolism.