UC Davis

The purpose of this trial was to determine if a yeast product (YP; ProDairy, Donaghys, Christchurch, New Zealand) given in water troughs increased milk production or altered rumen pH and blood parameters. Multiparous cows (930) in a commercial herd were randomly assigned to 1 of 4 pens as they reached 30 DIM. Milk yield, fat, and protein were measured every other week for 11 wk. Two of the 4 pens received YP at the rate of 9 mL/cow per day. All 4 pens were fed the same diet (525 g/kg of DM, 186 g/kg of CP, 220 g/kg of ADF, 329 g/kg of NDF, 43.8 g/kg of fat, 188 g/kg of starch, 41.3 g/kg of lignin, and 81.9 g/kg of ash). Statistics were performed using PROC MIXED with random effects pens nested within treatment and the fixed effects of DIM, week, and parity. Average daily milk yield (43.1 and 44.8 kg, P = 0.042) for control and supplemented pens, respectively, were greater in YP pens. But milk fat (1.47 and 1.45 kg, P = 0.13) and milk protein (1.24 and 1.23 kg, P = 0.045) for control and supplemented pens, respectively, were lower in YP pens. Overall rumen pH (7.7 and 7.4, P = 0.044) and blood ketone bodies (0.73 and 0.64 mEq/L, P = 0.011) were also reduced in supplemented pens. Therefore, YP did increase milk yield and affect rumen pH and blood ketone bodies, but other conditions on the commercial dairy may have influenced the milk response to YP. Depending upon the ability of the dairy to manage a consistent water supply, the delivery of YP via water should be considered by nutritionists and managers. More research is needed to determine the influence of other factors on milk response to YP supplemented in the water supply.