BUNCHING SEASON IS UPON US!

At Miner Institute’s recent Open House, I gave narrated rides on a hay wagon through our dairy facility. As we approached a pen of cows we are currently conducting a dairy nutrition trial on, nearly every one of the 86 cows in the pen were bunched in 1/3 of the pen closest to the center of the barn. I was hopeful the “general public” wouldn’t perceive that we were forcing the cows to live in such close proximity to each other…it was a hot day. I used it as an opportunity to explain how this was an area of research we have been working to understand better. Interestingly, on the other side of the barn, our close-up dry cows were also bunched away from the North end of the barn. While we don’t totally understand why cows do this, research conducted at Miner Institute by Bartlett et al., (2025), found that while bunching occurred when temperature was greater than 66°F (19°C), it is not the only factor and does not determine where bunching behavior occurs. Light intensity seems to be a primary motivating factor with cows seeking the darkest areas of the barn at Miner Institute.

Recently, my home farm transitioned to robots. A week ago, I was in the barn and noticed that nearly the entire pen of 1st calf heifers were bunched to the center of the barn. You can imagine what that does to animal flow to and from the robots which are positioned to the left at the end of the alley in the images at right. The fans were on full speed and I felt cool standing at the north end of the barn but the cows obviously preferred to be bunched at the other end. The top picture definitely demonstrates how the cows are choosing to move to the darkest part of the barn. While bunching behavior has adverse impacts on all dairy systems with reduction in lying time, etc., robot farms may have additional challenges with disruption in animal flow in key areas. To reduce light intensity, I suggested we close the North doors at the end of the alley. The bottom picture was taken at the same time of day (~1:30 pm) a week later on a similar warm, sunny day. Even without changing the side curtains or the feed alley overhead door, cows didn’t seem to bunch to the center of the barn as much…making the alley to the robots less congested. If you’ve had success in reducing bunching behavior in your herd, please reach out to me at ballard@whminer.com. We’d like to continue to investigate strategies to mitigate bunching behavior.

— Katie Ballard

ballard@whminer.com