When Mother Nature decides to turn on the summer heat, we have come to expect drops in milk yield and dips in reproductive performance. Another negative consequence of heat stress for today's cows is the risk of rumen acidosis.
"The modern day cow experiences heat stress much quicker than our grandfather's cows did," said Lance Baumgard, Iowa State University, during his presentation at the Central Plains Dairy Expo in Sioux Falls, S.D. "She's a bigger cow, making more milk and generating more heat," he explained.
A few factors contribute to the heightened risk of rumen acidosis. Under normal conditions, a typical cow eats 10 to 20 meals per day. A heat-stressed cow may only visit the feedbunk three or four times, so she's either eating less overall or slug feeding and consuming more per meal. She's also more likely to sort her feed, selecting more concentrates and less roughage. These behaviors all have negative effects on rumen health and, in turn, milk production.
A decline in feed intake also means less rumination. This leads to a reduction in saliva production, which cows use to buffer the rumen and keep pH levels in check. Even further, a hot cow that is panting and drooling is expelling much of this valuable fluid onto the floor.
"We want saliva in the rumen," Baumgard said. "The last place we want it is on the ground."
The eating behaviors that impact rumen health and milk production can be minimized by feeding early in the morning and later at night (when temperatures are cooler), pushing up feed more often, and removing old and potentially moldy feeds. Maintaining fiber levels and adding metabolic modifiers can also help. Ample quantities of fresh water is also a must, he said.
In the end, though, Baumgard explained that these nutritional strategies won't do much good if you don't first invest in cow cooling.
"By far, the biggest impact you can have to alleviate the negative consequences of heat stress is physically modifying the environment with shade, fans, soakers and misters," he said. With these heat abatement strategies in place, you can maintain milk production and rumen health by keeping saliva in the cow, where it belongs.
(c) Hoard's Dairyman Intel 2015
March 30, 2015
