Performance, blood parameters, ruminal fermentation and microbial community of dairy cows supplemented with <i>Saccharomyces cerevisiae</i> fermentation product from dry-off to early lactation

Dairy cows experience oxidative stress, inflammation, and immune dysfunction during the transition from dry-off to early lactation. Postbiotics such as Saccharomyces cerevisiae fermentation product (SCFP), consisting of nonliving microorganisms with or without their components, have beneficial effects on the production efficiency and immune function of dairy cows. The objective of this study was to evaluate the effects of SCFP on milk production, milk composition, ruminal fermentation, blood metabolites, oxidative status, inflammatory responses, and the ruminal microbial community in Holstein dairy cows supplemented from the day of dry-off through early lactation. Two hundred cows were blocked on the basis of parity, BCS, milk yield, and the time of dry-off and were randomly allocated to specific treatment groups within each block. The treatments included the control group (CON, n = 100) receiving basal diets with no SCFP supplementation and the SCFP group (n = 100) receiving basal diets supplemented with 19 g/d of SCFP from d -60 to 60 relative to parturition. Milk yield-monitored for all 100 cows per treatment-was tracked until d 140 postpartum. In parallel, ruminal fluid, feces, milk, and blood samples were collected from a subset of cows (n = 20/treatment) during the treatment period for further analyses. Data were analyzed via the MIXED procedure in SAS (SAS Institute Inc.). The results revealed that the average milk yield of dairy cows in the SCFP group was greater than that in the CON group (43.93 vs. 42.08 kg/d, P = 0.04, n = 100) during the treatment period and remained greater (41.92 vs. 39.98 kg/d, P = 0.04, n = 100) throughout the 140 d postpartum recording period. Cows fed SCFP had significantly lower serum β-hydroxybutyrate and nonesterified fatty acid concentrations than did those in the CON group. Compared with the CON group, the SCFP group presented greater levels of superoxide dismutase and lower malonaldehyde concentrations. The SCFP group also presented a greater total antioxidant capacity prepartum and higher glutathione peroxidase levels postpartum. Additionally, the SCFP group had lower concentrations of proinflammatory factors, such as IL-1β, serum amyloid A, and haptoglobin, throughout the treatment period, indicating a stronger anti-inflammatory capability. Overall, SCFP supplementation improved the ruminal environment, reduced oxidative stress and the inflammatory status, and ultimately increased milk production.