Editor's note: The following article was published by the William H. Miner Institute of Agriculture in the March 2014 issue of the Miner Institute Farm Report.

Switching pens and regrouping is a fact of life for dairy cows on most farms these days. Depending on size and management strategy, during her lactation cycle a typical cow might be housed in a fresh pen, high production pen, low production pen, far-off dry pen, and close-up pen.

She may also transition between a sick or hospital pen and her normal housing. It’s also likely that stocking density will vary among these housing situations. The interaction between regrouping and stocking density has had very little attention despite how often cows are asked to adapt them.

The Animal Welfare Program at the University of British Columbia addressed this situation in a recent edition of Journal of Dairy Science . Behavioral data from 72 mid-to-late lactation Holstein cows averaging 42 lbs of milk per day was collected.

Cows were housed in pens containing 12 or 24 freestalls (either 3 rows of 4 stalls or 3 rows of 8 stalls), milked twice daily, fed a TMR (52% forage and 48% concentrate), and provided free access to water. Feeding space was constant at 23 inches of bunk space per cow. Stocking density at the freestalls varied from severely undercrowded (4 stalls per cow) to undercrowded (2 stalls per cow) to at-capacity (1 stall per cow). Cows were regrouped a total of 8 times to progress through the various combinations of freestall stocking density and pen size.

Lying and feeding behaviors were monitored from 1 day before regrouping to 1 day after regrouping. Social aggression at the feed bunk was monitored for 3 hours following the delivery of feed on the day before and after regrouping. Change in stocking density affected the cows’ response to regrouping. When cows were moved into a pen with a relative higher stocking density, time spent lying following regrouping decreased.

Alternatively, when cows were moved into a pen with a lower stocking density, their total lying time increased. However, the size of the pen also played an important role. When cows were moved into a smaller pen from a larger pen, a decrease in lying time occurred and vice versa. Due to the consistency in feed bunk stocking density, there was no effect on feeding behavior. This suggests that relative pen size does not affect feeding behavior.

Similar to lying time, social aggression increased when stocking density increased and decreased when stocking density decreased following regrouping. These data provide some insight on how the combined effects of stocking density and regrouping might interact. The major limitation of this study was the range in stocking density included, which went from severely undercrowded (25% capacity of freestalls) to a maximum of an at-capacity pen (i.e. 100% stocking density).

As these stocking densities would not reflect what a cow would likely face when moving between pens in commercial facilities, there remain unanswered questions. Evaluating the response of cows moving among at-capacity pens and varying degrees of overstocking would provide a basis for estimating the cost to a cow of regrouping within an environment that she will likely be challenged with.

On the other hand, these data do suggest the importance of keeping hospital pens and fresh pens understocked to reduce the challenges inherent in these pens, especially as it will likely be a smaller pen than a cow’s normal home pen.

Peter Krawczel was a graduate student at Miner Institute and earned his Ph.D. in animal behavior from the University of Vermont in 2011. Peter is now a Dairy Research and Extension Specialist in the Department of Animal Science at the University of Tennessee in Knoxville.