Yeast Culture Supplementation Effects on Systemic and Polymorphonuclear Leukocytes’ mRNA Biomarkers of Inflammation and Liver Function in Peripartal Dairy Cows †

SIMPLE SUMMARY: During the transition period (3 weeks pre- to 3 weeks postpartum), dairy cows experience metabolic and immune alteration that can lead to a higher incidence of health disorders during early lactation. Therefore, we proposed the supplementation with yeast-based products in dairy cows’ diets during the transition period as a nutritional strategy to enhance the immune responses during this challenging period. Our results suggest that yeast culture could stimulate a more active inflammatory response, with signs of a resolution of the inflammation in transition cows; however, the specific mechanism of how bioactive compounds in yeast culture elicit this response during the transition period remains unknown. ABSTRACT: This study evaluated the effects of feeding a commercial yeast culture on blood biomarkers and polymorphonuclear leukocyte (PMNL) gene expression in dairy cows during the transition period until 50 d postpartum. Forty Holstein dairy cows were used in a randomized complete block design from −30 to 50 d. At −30 d, cows were assigned to a basal diet plus 114 g/d of top-dressed ground corn (control; n = 20) or 100 g/d of ground corn and 14 g/d of a yeast culture product (YC; n = 20). Blood samples were collected at various time points from −30 to 30 DIM to evaluate blood biomarkers and PMNL gene expression related to inflammation, liver function, and immune response. Liver function biomarkers, gamma-glutamyl transferase (GGT) and albumin were greater and lower, respectively, in YC cows in comparison to control. However, these biomarkers remained within physiological levels, indicating an active inflammatory process. Genes in PMNL expression related to inflammation (NFKB1, TNFA, TRAF6), anti-inflammation (IL10), and cell membrane receptors (SELL) were upregulated in the YC group in comparison to control. These results suggest that YC could stimulate a more active inflammatory response with signs of a resolution of inflammation in transition cows.