Effects of supplementation with Bacillus licheniformis 809 and Bacillus subtilis 810 on colostrum quality, productive performance, nutrient digestibility, and metabolic responses of dairy cows during the transition period

The objective of this study was to evaluate the effects of supplementation with Bacillus licheniformis 809 and Bacillus subtilis 810 on DMI, colostrum quality, milk yield and composition, nutrient digestibility, feeding behavior, metabolic, and health parameters of dairy cows during the transition period. Sixty multiparous Holstein cows were divided into 2 groups: a control group (CG) receiving no additives and a Bacillus group (BG) receiving 3 g of a direct-fed microbial (DFM; 3.2 × 10⁹ cfu/g of DFM). Monitoring was carried out from 30 d before to 60 d after calving, including assessments of milk production, colostrum quality and composition, milk composition, DMI, BW, BCS, energy balance, blood biochemical parameters, feeding behavior, and nutrient digestibility. Milk production was corrected to 3.5% fat (FCM), and feed efficiency was calculated for both milk yield and FCM. Data were analyzed using JMP Pro 14 software, with significance declared at P < 0.05. Results demonstrated that BG cows had greater pre- (14.0 vs. 13.4 kg) and postcalving (20.6 vs. 20.1 kg) DMI, milk yield, fat yield, protein yield, and ECM yield (40.38 vs. 39.56 kg/d), with no differences in feed efficiency. Negative energy balance was reduced in the BG (-3.99 vs. -5.81 Mcal/d), whereas SCC (529.0 vs. 819.1 × 10³ cells/mL) and the percentage of cows with SCC >200,000 cells/mL was reduced (48.2% vs. 75.0%) for BG versus CG. Colostrum quality was also improved in the BG, with higher average Brix values (26.5% vs. 23.9% Brix) and a greater percentage of cows with ≥23% Brix (86.96% vs. 56.52%). No differences were observed in urinary pH, BCS, or most metabolic parameters, except for a trend toward increased leptin and IgA levels in the BG. Fecal scores were improved in the BG during the prepartum period, as was NDF digestibility throughout the entire trial. Lastly, time spent eating (min/d) during before and after calving also tended to be greater for BG cows. Hence, It is concluded that Bacillus spp. supplementation increases DMI, milk production, and fiber digestibility, and colostrum quality. It also reduces milk SCC and negative energy balance and favors immune response, with a trend toward higher serum IgA levels.