RESULTS Production Performance One hundred forty-two cows completed the experimental period. Reasons for cow removals are listed in Table 3. The milk yield variables milk, 3.5% FCM, and ECM were higher (P < 0.01) for cows supplemented with YC and YC+EHY compared with control. Although weekly treatment differences in milk were not statistically evaluated, milk yield for cows supplemented with YC and YC+EHY was consistently higher over the initial 11 wk of the experimental period compared with controls (Figure 1). Those supplemented with YC+EHY tended to exhibited higher starting milk yields (wk 2–4). Fat percentage was unaffected (P > 0.05) by treatment. Protein percentage was higher (P < 0.01) for cows supplemented with YC+EHY compared with control; YC was not different from either YC+EHY or control. Weekly protein profiles (Figure 2) illustrated that by wk 2 of experiment, cows supplemented with YC+EHY tended to have a consistently higher protein percentage than control cows. Lactose percentage was not affected (P > 0.05) by treatment. Milk fat yields were higher (P < 0.01) for cows supplemented with YC and EHY+YC compared with control cows. Milk protein yields were higher (P < 0.01) for EHY+YC compared with control cows, with YC cows not different from either. Figure 3 illustrates that protein yields tended to be higher for cows supplemented with YC+EHY in wk 2 through 4; thereafter
both YC and EHY+YC were similar and tended to be higher than control during the remainder of the trial period. Treatment did not affect MUN, with all treatments ranging from 11.1 to 11.4 mg/dL. Treatment did not affect BW or BCS (Table 4).
Health and Mastitis
Health disorders were not affected (P > 0.05) by treatment (Table 5). Somatic cell count during the 14wk experimental period was lower (P < 0.01) for cows supplemented with YC+EHY compared with control and YC (Table 6). Figure 4 illustrates that the treatment effect on SCC appeared to be more pronounced during the second half of the trial period. During wk 1 through 7 of trial, no differences among treatments were observed; however, during wk 8 to 14, cows supplemented with YC+EHY had lower (P < 0.01) SCC compared with control and YC. New clinical cases of mastitis were numerically lower for cows supplemented with YC+EHY compared with control and YC. This difference was mainly exhibited during wk 8 to 14 of the trial.