Effects of feeding direct-fed Bacillus subtilis and Clostridium beijerinckii on health, performance, and blood biomarkers during the transition period and early lactation in Holstein cows

This experiment was conducted to evaluate the effects of 4 dietary treatments on dairy cow performance: (1) Bacillus subtilis (2 strains provided together at 2.0 × 10⁹ cfu/d), (2) Clostridium beijerinckii (6 environmental strains provided together at 4 × 10⁶ cfu/d), (3) the combination of the same B. subtilis and C. beijerinckii strains at these same doses, and (4) a control diet without C. beijerinckii and B. subtilis. Treatments were administered from 21 d relative to expected calving until 70 DIM. Seventy-one multiparous Holstein cows were randomly assigned to one of 4 treatments in a complete block design. The experimental diets consisted of a basal TMR top dressed, both prepartum and postpartum, with B. subtilis (CER), C. beijerinckii (BJE), the combination of C. beijerinckii and B. subtilis (CBJ), or no supplementation (CON). Cows were milked twice daily, and milk samples were collected on 7, 14, 28, 42, 56, and 70 DIM. Milk yield and DMI were recorded daily, and BW and BCS were recorded weekly. Colostrum was obtained from each cow at the first milking after calving. Colostrum weight, Brix value, and estimated IgG concentration were recorded immediately after collection. Blood samples were taken for plasma analysis on d -25 ± 5 (used as a covariate), -8 ± 3, 7 ± 2, 28 ± 2, and 70 ± 2 DIM. There was a tendency for higher colostrum IgG yield in CER compared with CBJ (567 vs. 417 g, respectively). A treatment × week interaction reported that cows in CER had higher milk fat content than BJE in wk 1 (5.32% vs. 4.60%) and higher milk fat concentration in wk 4 compared with CON (4.52% vs. 3.73%), BJE (4.52% vs. 3.83%), and CBJ (4.52% vs. 3.83%). During the first week after calving, cows in the BJE group had higher milk protein and milk CN concentrations compared with cows in CER and CBJ. Cows in CER tended to have greater plasma triglycerides than CON and had lower plasma gamma-glutamyl transferase (GGT) concentrations compared with CBJ. Cows in CER also had higher plasma cholesterol concentrations than CON. Cows in BJE had greater plasma total protein and globulin concentrations than CON. In conclusion, CER increased milk fat content and colostrum IgG yield, while also increasing plasma triglycerides and cholesterol, which may be associated with improved lipid transport. Our data suggest that cows in CER and BJE may have experienced lower hepatic stress, as indicated by reduced plasma GGT concentrations. Feeding BJE increased milk protein and CN content in the first week after calving but did not consistently affect health or performance.