Heat stress occurs when environmental temperature, radiant energy, humidity, and wind speed create a warmer situation than the animal's thermal neutral zone temperature record. Scientists from the Autonomous University of Barcelona analyzed the data provided by more than 10,000 inseminations from four cattle over a three-year period. Using weather data from a nearby weather station, the scientists calculated heat stress levels in the days immediately before and after each insemination.
As published in the journal Theriogenology , they found that elevated levels of heat stress at key points reduced the chances of fertilization success. As, for example, high heat stress three days before insemination reduced fertility, probably due to ovulation failure . This failure was 3.9 times higher in cows inseminated during a hot period (May to September) than in the colder periods of the year.
Heat stress on the day of insemination is also important, as it can affect eggs, sperm and embryos. Furthermore, a high maximum temperature the day after insemination also reduces conception rates.
