Heat and drought impact cow conception
The breeding success in the South Dakota cowherd was quite variable this summer because of heat and drought. Extension Beef Reproduction Specialist George Perry explains cows that were bred in the early part of the summer settled a pregnancy quite well but when summer temperatures began to spike, many cows were just too hot to breed.
“Where we’ve seen the majority of problems occurring this year are actually the animals trying to be bred end of June and into July when we had the really hot weather,” Perry said. “If we raise the rectal body temperature as little as two degrees, we can actually retard embryo growth and therefore we don’t get near as good of pregnancy rates.”
Perry says heat stress may also have impacted semen quality of bulls.
“On bulls there is more of a lasting effect of that heat, even heat for a short period of time, since spermatogenesis in the bull is a 61-day process. If the bulls get too hot or their testes get too hot, the sperm that is actually being formed can be impacted and actually impact fertility up to two months later depending on how severe it was.”
The heat stress was compounded by the drought, with summer pastures falling short for many cows’ nutritional needs.
“When she starts losing condition, unless that embryo is well established it’s one of the first things that can be lost,” he said.
Perry urges cattlemen to monitor and boost their herd’s body condition now if needed before winter sets in as after weaning is the easiest time to improve body score – setting the stage for successful calving.
To learn more about this topic, visit the beef tab on igrow.org. More information on fertility and body condition scoring will also be presented at the 2012 Applied Reproductive Strategies in Beef Cattle Conference. The conference will be held in Sioux Falls, SD, Dec. 3 and 4. The full program and list of speakers is available at http://muconf.missouri.edu/ARSBC-SouthDakota.
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