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Effects of yeast product supplementation on immunity and uterine inflammation in transition dairy cows
The objective of this study was to assess the effects of supplementing a yeast product derived from Saccharomyces cerevisiae on immunity and uterine inflammation in transition cows. Forty multiparous Holstein transition cows were blocked by expected calving date, and randomly assigned within block to 1 of 4 treatments (n = 10) from 21 d before expected calving to 42 d postpartum. Rations were top-dressed with yeast culture plus enzymatically hydrolyzed yeast (Celmanax®, Vi-COR®, Mason City, IA) at the rate of 0, 30, 60, or 90 g/d throughout the experiment. Blood samples collected on -21, -7, 1, 4, 7, 14, 21, and 35 d relative to calving were incubated with E. coli (# 51813) to assess the ability of blood to kill bacteria. Uterine samples were collected on d 7 and 42 postpartum by cytobrush technique to determine neutrophil populations and relative abundance of transcripts involved in inflammation. Fecal samples were collected on d 7 and 21 for analysis of immunoglobulin A (IgA) concentration. Data were analyzed using mixed models with repeated measures over time. The percentage of E. coli killed by whole blood was not affected by yeast treatments (P = 0.28). Uterine neutrophil populations were much greater in samples collected on d 7 compared with those on d 42 (32.0 vs. 7.6 ± 3.7 % of cells, P < 0.01), indicating greater neutrophil infiltration immediately after calving, but no treatment (P = 0.53) effect was detected. There were significant (P ≤ 0.01) day effects for IL-6, IL-8, neutrophil myeloperoxidase, and neutrophil elastase, reflecting greater abundance of these transcripts in uterine tissues collected on d 7 compared with d 42. Interestingly, there was a quadratic dose effect (P = 0.02) for IL-6, indicating that 30 and 60 g/d decreased uterine IL-6 mRNA. The mRNA abundance of neutrophil myeloperoxidase and elastase was increased (P < 0.05) by yeast product. Yeast product quadratically increased fecal IgA concentrations (P = 0.03), suggesting that 30 and 60 g/d doses enhanced mucosal immunity. Yeast product supplementation did not affect whole blood bacterial killing ability, but modulated uterine inflammatory signals and mucosal immunity in transition dairy cows.
Keywords: immunity, transition cow, yeast