Will summer heat affect breeding

Producer Question from 2012

Q.  Will the heat during the summer affect the breeding on the cow herd? I turn my bulls out in the middle of July for Apr-May calves. (May 18, 2012)

A.  The heat we are experiencing can affect reproductive performance of beef females and males. Part of the concern is that it is not only hot during the day, but it doesn't seem to cool down in the evenings. Therefore, it is difficult for the cattle to get rid of the heat load that was built up during the day. On the females, heat stress can effect embryo implantation. Heat stress can also affect bull fertility. Heat stress affects spermatogenesis (production of sperm). Because the testicle and tubules store sperm, the effect of heat stress doesn't show up until about 45 to 60 days post?heat stress. One of the mechanisms to keep the testicles cool is that the muscles relax allowing the testicles to hang further from the body.

What can you do? Allow access to plenty of clean water. Most pastures have trees that will provide shade. Avoid working cattle during the hot temperatures. Finally, keep the flies under control. Seems like when cattle have a fly load, then tend to bunch. This causes less air circulation around the cattle and increased heat is generated.

Dr. Rick RasbyDr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska–Lincoln, Lincoln, NE