Helping dairy cows through extreme heat

COLUMBIA, Mo. – Heat waves put extra stress on livestock. A University of Missouri Extension dairy specialist advises taking specific, ongoing steps for dairy cows throughout heat waves.

Heat abatement

In a press release, Scott Poock, state extension specialist in veterinary medicine, said, “Dairy cows become heat-stressed starting at 65 degrees Fahrenheit. Fans should start running at that temperature and by 70 degrees, soakers should be started.”

Place soakers and fans in the holding area near the parlor, Poock said. “This is the spot on the farm that cows will experience the most heat stress during the day, and soakers and fans should be running at each milking, not just during the heat of the day.”

Soaking the coat of the cow – with large drops of water rather than small, misty droplets – allows evaporative cooling to occur. Providing comfortable stalls will encourage cows to lie down more quickly and for longer periods, which will be a benefit during heat stress.

Nutrition needs in heat stress

The cow’s dry matter intake tends to decrease during heat stress, said Poock. “The energy density of the ration is usually increased. But that increase can expose the cows to potential subacute ruminal acidosis (SARA). To help mitigate SARA, add sodium bicarbonate to help improve rumen health.”

Sodium bicarbonate can be fed at 0.5%-1% of the diet (1/4 to 1/2 pound per head per day).

Adding fat to the diet can help increase energy density without affecting SARA. However, added fat cannot exceed 2%-3% of the diet because it will depress milk fat production.

Reproduction management in heat stress

There is always a decrease in fertility during heat stress, and that means decreases in conception and pregnancy rates.

“The producer can use beef semen and/or embryos to try to improve this,” Poock advises. “Because most embryo loss during heat stress occurs within the first several days after conception, using embryos that are seven days old can improve pregnancies. At Foremost Dairy we have used embryos and seen an increase in pregnancies.”

Poock said synchronizing the cows and using timed AI can overcome decreased estrus expression during heat stress. “It is important to utilize proven synchronization protocols and be 100% compliant,” Poock said.