Cows eat less when they are warm, a factor that researchers say leads to a 50% drop in milk production. But these drops in production can reach up to 70% in hot weather.
In a search to account for the remaining 20%, researchers conducted a trial with 48 Holstein cows housed in temperature-controlled stalls. Over the course of two weeks, half of the cows were exposed to heat of around 98 degrees, while the others were housed in neutral conditions. All the cows were milked twice a day, and the researchers tracked everything from their vital signs to their weight, feed intake and milk yields. The research was published in the Journal of Dairy Science.
As expected, hot cows’ milk production decreased and heat-stressed cows had higher insulin levels. They also ate and drank less.
When the researchers analyzed blood samples from the cows, they found that heat-stressed cows developed intestinal permeability, or leaky gut, in just three days. The condition occurs when bacteria and other material “leaks” through weakened parts of the intestinal wall. This can cause inflammation in cows, as their immune system kicks in once it encounters the bacterial invaders.
But researchers have also found a way to dampen cows’ reactions to heat. When they fed the heat-stressed animals a special blend of organic acids and pure plants, their intestines became less permeable, they ate more, and they produced more milk.
This dietary solution could help prevent some of the billions of dollars in economic losses associated with heat-stressed cows, the researchers write. “This has immediate application,” said study co-author Joseph McFadden, a dairy biologist at Cornell University, in a press release. The research could eventually lead to changes in food formulation, he says.
Heat stress develops with increased total intestinal permeability, and dietary organic acid and pure botanical supplementation partially restore lactation performance in Holstein dairy cows