Impact of pen move events on rumination time, milk yield, and water intake in dairy cows

<h2>Abstract</h2> Cow regrouping associated with pen move events (PME) within a dairy farm disrupts the social dynamics of cows in the herd and impacts cow behavior and performance. The objective of this study was to evaluate the impact of PME and cow move group size on rumination time [RT; minutes/d], milk yield [MY; kg/d], and water intake [WI; L/d] of dairy cows up to 5 d post-move. A retrospective study was conducted on an organic dairy farm in central Texas, which consisted of 5,420 independent cow move events collected from 1130 crossbred dairy cows. Cow-related variables were retrieved from herd management software, daily RT and WI were retrieved from sensor boluses, and daily MY was retrieved from milk meters on the farm. Statistical analyses were conducted in R using repeated measures in a mixed-effects model controlled for stage of lactation, temperature-humidity index, and parity with cow as a random effect. We identified a 3-way interaction effect between parity, stage of lactation, and day since the pen move on RT. During early lactation, the reduction in RT was more pronounced in primiparous cows on d 2 to d 5 post-PME compared with d-1. In multiparous cows, during the dry period, RT was significantly reduced compared with d-1. Similarly, MY decreased during early lactation in multiparous cows and during late lactation in primiparous cows. A parity-stage of lactation-d 3 way interaction was observed in WI, with decreased WI in primiparous cows during early lactation after PME. In contrast, WI increased in multiparous cows in the dry period and mid lactation. Furthermore, WI, RT, and MY were also impacted by the size of the cow move groups (single, small, or large) and varied across different parities; primiparous cows moved in larger groups showed a 10% drop in RT as compared with 6% drop in multiparous cows moved in large groups. Compared with primiparous cows, multiparous cows experienced a more pronounced decline in milk yield when moved in small or large groups, along with a significant reduction in water intake in the large group moves. We demonstrate that daily RT, MY, and WI are affected by pen moves events, with the impact dependent on the parity of the cows and the size of the cow move group.