CASE STUDY: Effect of pen change on milk yield by dairy cows in 2 commercial herds

The objective of this experiment was to determine the effect of pen change on daily milk yield by dairy cows over the first 10 d after changing pens. The study was conducted during the fall/winter months of 2010/2011 in 2 Wisconsin dairy herds. Study cows were randomly assigned to either treatment (M) or control (NM). On d 0, the M cows were switched between study pens, whereas NM cows remained in their original pen throughout the study. Daily milk weights for M and NM were analyzed for 10 d before d 0 and 10 d after d 0 using PROC MIXED of SAS with parity, treatment, day, and treatment × day interaction as fixed effects and cow within treatment as a random effect. For herd A, n = 154 and 152 for M and NM, respectively. Herd A least squares means for average daily milk yield were 32.0 and 32.4 kg/d per cow for M and NM, respectively. For herd B, n = 137 and 142 for M and NM, respectively. Herd B least squares means for average daily milk yield were 49.3 and 49.4 kg/d per cow for M and NM, respectively. The least squares means for M and NM groups did not differ by least significant difference test for any day within a herd. Moving groups of animals between pens did not have deleterious effects on milk yield.