Effects of feeding a fibrolytic enzyme to Holstein dairy cows on milk production and reproduction

Objective: Our objective was to determine whether a TMR supplemented with an exogenous fibrolytic enzyme product (EFE) improved milk production and reproduc-tion in a commercial dairy.Materials and Methods: Holstein cows were random-ly assigned to 1 of 4 study groups: (1) primiparous control (PC; 2 pens; 486 cows) or (2) primiparous EFE (PT; 2 pens; 483 cows) fed a TMR with EFE, and (3) multipa-rous control (MC; 3 pens; 1,023 cows) or (4) multiparous EFE (MT; 3 pens; 998 cows) fed a TMR with EFE. The EFE had a declared minimum of 44,750 units/g xylanase and was fed at a rate of 2 g/cow per day during the pre -calving period and 4 g/cow per day during the lactation period. Only cows that were fed the control or EFE sup-plement in the TMR for at least 2 wk in the close-up pen were enrolled in the study. After calving, cows continued in their respective treatments in control or EFE groups in high milking pens for 180 d.Results and Discussion: There was no difference in mean days of exposure to EFE among PC, PT, MC, and MT pens. The PC had greater milk fat yield, percentage fat, FCM, and ECM compared with PT. The MT had lower milk fat yield and FCM than MC. Median days to confirmed pregnancy was 10 d less in PT compared with PC.Implications and Applications: Feeding a TMR sup-plemented with this EFE may have increased the energy available to primiparous cows, which reduced their days to confirmed pregnancy.