Pound for pound, the smaller the cow the better she can keep herself cool during those hot summer days.
While the total days per year that cause heat stress aren’t that numerous for much of Canada, there’s a day or two lag in the full impact on the cows. When you add up the hot days plus the lag days, the drag on cow feed intake, milk production, and fertility can stretch out over a good part of the growing season.
Eric Baumann, director with Jersey Ontario and Ph D candidate at Laval University, says that there are daily management decisions that help cows manage heat stress, but the cow’s own frame also plays a role in how well she can maintain production and fertility while coping with hot weather.
Using the example of a tennis ball vs a soccer ball in the interview below, Baumann explains that a smaller framed cow, either because of breed or within breeds, is better able to dissipate heat because of its higher surface to mass ratio.
Breeding for more moderately-framed cows is a long-term goal, of course. Baumann says that in the interim, it’s important to spend some time gauging barn conditions on those warm summer days. We want cows spending time at the bunk and resting, so farmers should too, he says. The five minutes you spend standing in the bedding area and at the bunk should tell you whether or not it’s cool enough for a cow to enjoy doing the same.
Hear more from Baumann below in this interview recorded at the Ottawa Valley Farm Show: