Effects of feeding a native rumen-native microbial live supplement during pre- and postpartum on health, performance, and blood metabolites of Holstein cows.

Rumen-native microbial supplementation can improve milk production by enhancing rumen function, but its effects on immunity, health, and mammary development are less known. This study evaluated Galaxis Frontier (GF, Native Microbials, San Diego, CA) top dressed daily at 5 g/cow per day, administered either pre- and postpartum (wk -4 to 16) or postpartum only (wk 1 to 16). Microbial feed supplementation consisted of 2 × 10⁷ cfu/g of Pichia kudriavzevii, 2 × 10⁶ cfu/g of Clostridium beijerinckii, 2 × 10⁷ cfu/g of Ruminococcus bovis, and 2 × 10⁷ cfu/g of Butyrivibrio fibrisolvens. Sixty pregnant Holstein cows were assigned to treatments as follows: (1) GF supplementation for 4 wk prepartum and 16 wk postpartum (Pre+PostG, 5 g/cow per day of GF; n = 20), (2) GF supplementation for 16 wk postpartum (PostG, 5 g/cow per day of GF; n = 20), and (3) control, no supplementation of GF (CON, n = 20). Orthogonal contrasts were used to determine the effect of the inclusion of the microbial additive during the postpartum period. Cow BW, BCS, and blood metabolites (glucose, nonesterified fatty acids [NEFA], and BHB) were monitored weekly or biweekly. Milk yield was recorded daily, components weekly, and health and immune parameters evaluated through wk 4. Mammary biopsies were collected on d 14 and 60. Prepartum supplementation (27 ± 2 d) reduced BHB (8.69 vs. 6.99 mg/dL) and NEFA (0.15 vs. 0.09 mM), increased calf birth weight (+2.3 kg), and improved colostrum yield (+2.0 kg) and protein content (+0.45 kg) versus CON. During wk 1 through 4, GF-supplemented cows (average Pre+PostG and PostG) exibited a more negative energy balance (-9.08 vs. -11.65 Mcal/d) but maintained DMI and milk yield, showed improved feed efficiency (2.18 vs. 2.38 kg/kg), and slight enhancement in immune function. From wk 5 to 16, GF-supplemented cows had lower BHB and increased milk fat (+0.17%). PostG cows had greater milk protein (+0.09%) and fat (+0.24%) than Pre+PostG cows. The GF-supplemented cows had a greater number of alveolar secretory units with more epithelial cells. Supplementation with GF improved colostrum yield and quality, calf outcomes, milk components, feed efficiency, and metabolic and immune parameters. Initiating supplementation postpartum yielded similar benefits with enhanced milk protein. Further research is needed to elucidate underlying mechanisms.