Peripartal supplementation of a blend of postbiotic and essential oil compounds influences ruminal fermentation while improving feed intake and milk production in transition dairy cows

This study aimed to evaluate the effect of a blend of postbiotics and essential oil compounds on lactation performance in dairy cows supplemented during the transition period until 60 DIM. Sixty-one Holstein dairy cows were enrolled in a randomized complete block design from -35 to 60 DIM and blocked according to expected calving day, parity, and previous lactation ECM. At -35 d before expected calving date (32 ± 3.8 d relative to actual calving), cows were assigned to either a basal diet plus 100 g/d of ground corn and 25 g/d of placebo (CTL; n = 30) or a basal diet plus 100 g/d of ground corn and 25 g/d of a blend of postbiotic and essential oil compounds, including but not limited to cinnamaldehyde and garlic oil (PE; n = 31). Cows were fed 1X/d with TMR, and treatments were top-dressed after feeding. From -35 to -22 DIM, cows were fed a far-off diet; from -21d until calving, cows received a close-up diet. From calving to 30 DIM, cows received a fresh cow diet, and from 31 to 60 DIM, cows were fed a postfresh diet. Blood samples and rumen fluid were collected at various time points from -35 to 60 d relative to calving (DRC). Data were analyzed using the MIXED procedure of SAS (version 9.4). Pretrial BW was greater (P < 0.01) in CTL cows compared with PE; therefore, pretrial BW was used as a covariate. Prepartal energy balance and postpartal DMI (as % of BW) were greater in PE cows than CTL. An increased milk yield (+2.8 kg/d) and milk protein yield were observed in PE cows compared with CTL. We observed a lower ruminal concentration of lactate in PE cows compared with CTL. We detected treatment × time interactions for the ruminal proportion of propionate and 2-methylbutyrate, which resulted in a greater proportion of propionate in PE cows compared with CTL at 28 DRC and 2-methylbutyrate, associated with a lower proportion in PE cows compared with CTL at -28 DRC. For blood biomarkers, PE cows had a greater concentration of γ-glutamyltransferase and a lower concentration of paraoxonase than CTL cows. These results indicate potential benefits of supplementation of postbiotic and essential oil compounds during the transition period to enhance lactation performance and ruminal fermentation profile in dairy cows.