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TIMELY TOPICS
The recent days have brought welcome relief from sweltering temperatures and humidity that have marked our summer so far. While the rain that came with the cooler temperatures has been most welcome, we are far from seeing the end of our drought conditions. One echo of this summer’s heat we are likely to see extend into the fall is in the fertility of our livestock.
Heat stress can reduce fertility in both female and male livestock. In cows, does and ewes, it occurs in the form of “silent heats,” or they simply stop ovulating. In bulls, bucks and rams, heat stress can cause a reduction in the number of sperm and the “motility” of those sperm still present, which means the sperm have a reduced ability to travel up the reproductive tract to fertilize the egg.
The problem is most serious for males. Infertility in a heat-stressed cow can lead to missing one calf. Heat stress in a bull can lead to the failure to breed 25 to 40 cows with that many missing calves. For bulls, bucks and rams, it may take 60 to 90 days after the hot weather for fertility to recover. So even if the bull does not need to breed cows or heifers until October or November, there could still easily be an echo of summer’s heat expressed in his ability to breed, especially if hot weather extends into September as it often can.
Most food animal veterinarians can conduct a breeding soundness examination to confirm the fertility and functionality of a bull, buck, or ram. Since most livestock producers rely on their breeding males to breed anywhere from five to 60 head of females, the cost of a breeding soundness exam is a small price to pay for some assurance fertile females can be successfully bred. An exam three to five weeks ahead of the breeding season is usually close enough to ensure the exam reflects what their fertility will be for the season and provides enough time to find a replacement male if necessary.
Farmers whose livestock are in the midst of breeding season can also have their bulls checked. Quick action to replace a compromised bull, if necessary, can save the farm from significant financial loss.
