By CELESTE BAUMGARTNER
Ohio Correspondent

LIBERTY, Ind. — The high, consistent heat this summer has caused breeding related problems in some cattle, said Kenneth Krom, DVM. In parts of the Midwest it was hot day and night - the cows didn’t get a break, their bodies did not get a chance to cool down.
Some cows are now returning to their heat cycles because they did not get bred. Other cows missed a couple of heat cycles and then resumed them again.

“The possibility is that they were pregnant and then due to the extreme heat they reabsorbed the embryo,” said Krom, whose veterinary practice deals mainly with cattle.

“I have also seen two cases where it was fairly certain that there was a death loss of adult cattle due to heat or early stroke,” he said.

One client told Krom that none of his embryo transfer recipient cows were pregnant. Another client’s herd had the lowest pregnancy rates it had had in three years.

“I checked cows for a dairyman and he had breeding dates from February into July - they’re calving year-round,” Krom said. “His early breeding dates - those in February, March and April, in that group of cows there was only one cow open. In the July group, where we were dealing with that heat, there was only one cow in that group pregnant. The same herd, same nutrition, same rations, same artificial insemination (AI) technicians. The only thing that was different was the time of year and the weather.”

Heat can cause problems in cows and bulls, Krom said. With cows it is a milder situation. On hot days the cows may be too hot to exhibit signs of estrus. That makes it difficult for AI technicians to determine proper breeding times. In more extreme cases the cow’s body temperature can get too high early in the pregnancy; that can kill the embryo.

Too high temperatures can cause temporary sterility in bulls. That causes problems both in bull-bred herds and herds that are artificially inseminated.

“Even if it doesn’t get hot enough to cause sperm damage or sperm loss, if the bull is hot enough and experiencing stress he may want to go stand under a shade tree instead of following and breeding cows like he is supposed to be doing,” Krom said.

Cows bounce back from heat stress more quickly than bulls. When cool weather comes a cow can get pregnant by her next three week cycle. If a bull experiences temporary sterility it can take approximately 40-45 days for it to have viable sperm again.

Producers are limited in what they can do to prevent heat stress, Krom said. They need to provide shade and plenty of water. Yet when temperatures in the 90s persist for a long period of time, especially with little cool off at night, there is little to be done.

As a result of the heat stress problem, many cows will probably be calving later next spring than what producers consider desirable.
“I’m sure there are going to be a lot of open cows, more than we would like to see, this fall,” Krom said.

Yet the situation is “hit and miss,” Krom said.

“I checked 114 cows for one client two weeks ago and he only had six cows open,” Krom said. “That is a really good percentage even in a good year.”