After the extremely cold temperatures across Oklahoma a few weeks ago, we are now seeing daytime highs of 70 F (or higher). It is important to remember that the calves born in single digit temperatures need to be monitored closely as the weather becomes dramatically warmer.
A calf’s health is significantly impacted by ambient temperature. The most comfortable range for young calves being between 55 and 70 F. This range is considered the thermoneutral zone for young calves where a calf can maintain its body temperature without expending extra energy. Heat or cold stress results in direct economic losses because of increased calf mortality and morbidity, as well as indirect costs caused by reduced weight gain, performance, and long-term survival.
Thermic stress in calves is observed not only with extremely high or low temperatures, but also extreme temperature variations. Variables such as relative humidity and wind speed can also contribute to thermic stress. Heat stress is actually harder on young calves than cold stress. When calves are heat stressed they lose appetite, eat less and are quicker to become dehydrated.
Thermoregualtion in calves is similar to that of adult cattle, but newborn calves have an immature “thermostat” and accordingly have more problems regulating body temperature during weather extremes.
Thermoregulation is the ability of homeothermic animals to keep their body temperature within a certain range despite being exposed to different ambient temperatures. A physiological core temperature is maintained by generating metabolic heat as well as exchanging heat with the environment. Cattle are able to adjust to adverse climate by means of acclimatization and adaptation. Extreme climatic conditions that cannot be compensated by thermoregulatory mechanisms result in thermic stress.
As the weather becomes more pleasant and daytime highs exceed 70 F, keep an eye on your young claves soaking up the sun. The signs of overheating may not be as dramatic as the signs of cold stress but can be just as damaging to a calf’s health. — Mark Z. Johnson, Oklahoma State University Extension beef cattle breeding specialist
