Effects of a blend of Saccharomyces cerevisiae fermentation-derived postbiotic and essential oil supplementation on the performance of transition dairy cows

We aimed to evaluate the effects of a blend (PE) of Saccharomyces cerevisiae fermentation-derived postbiotics (SCFP) and essential oil compounds (EO) on performance, rumen fermentation profile, nutrient digestibility, nitrogen metabolism, blood metabolic profile and immune parameters in transition dairy cows from -35 d to 63 d postpartum. Sixty-two multiparous Holsteins, at 245 ± 3 d of pregnancy, were assigned to control (CON; n = 31) or a blend of SCFP and essential oil compounds (PE; n = 31) in a randomized block design. Diets were formulated based on CNCPS guidelines. The treatment group was top-dressed with PE (25 g/d) on the ad libitum-fed TMR to individual cows. During the prepartum period, BCS and BW were measured weekly. For lactating cows, DMI, milk yield, and BW were recorded daily; milk samples were collected twice weekly for component analysis; and BCS was recorded weekly. Colostrum quality was measured using a Brix refractometer. Rumen fluid was collected at weeks -5, -2, and +2 for fermentation profile analysis. Fecal and urine samples were collected at weeks -4, -1, +2, +4, and +6 for digestibility and nitrogen metabolism analysis. Blood samples were collected on d -35, -28, -14, -7, +3, +7, +14, and +21 relative to calving. Data were analyzed using the GLIMMIX procedure in SAS using treatment, week, interactions, and block as fixed factors, while cows nested in treatment were used as a random factor. Significance was declared at P ≤ 0.05 with tendencies noted at 0.05 <P ≤ 0.1. For prepartum cows, no effects of PE were observed on DMI, BCS, BW, and energy balance. However, postpartum DMI and milk yield were greater during wk 7 and 8 for cows fed PE. Fat-corrected milk and ECM yield were greater for cows fed PE during wk 5, 7, and 8 post-calving. No effects were observed on milk components except for a lower tendency in SCS during wk 6, 7 and MUN in cows fed PE. Fat concentration tended to be greater in colostrum for cows fed PE, but Brix score and colostrum protein levels were unaffected. Supplementing PE tended to decrease the urine nitrogen output, and no effects were observed on rumen fermentation profile, nutrient digestibility, or urine metabolites, both pre- and postpartum. Among plasma metabolites, PE increased the levels of gamma-glutamyl transferase and BUN within physiological levels in prepartum cows. Alkaline phosphatase tended to be lower with PE on d -7. In the postpartum period, the albumin-to-globulin ratio was greater, and Ca concentrations were lower on d +14 post-calving with PE. In prepartum cows, PE supplementation tended to increase macrophage percentage while decreasing the proportion of non-neutrophils. The percentage of neutrophils during postpartum tended to be lower with PE. Other immune parameters, including oxidative burst and neutrophil phagocytosis, were not affected by PE. In conclusion, the PE prototype improved performance, nitrogen utilization without affecting rumen fermentation profile or nutrient digestibility. Supplementation with PE had selective effects on blood metabolites and immune parameters. Overall, these results suggest that supplementing blend of SCFP and EO can enhance lactational performance and modulate immune status in transition cows.