Hot weather can be very hard on livestock, especially if it is also humid. Humidity makes it harder to dissipate body heat.
Heat and humidity of summer can be very stressful for sheep. It is most dangerous when temperatures soar suddenly and remain high with little cooling at night. When this happens it does not give the sheep time to adapt to the change in weather. Sheep that are overheated can be prone to bloat, even though they are acclimated to the pasture they are in. Most heat dissipates from sheep under their bellies and between their back legs. Sheep also cool themselves through panting and respiration. Excessive respiration causing stress on the lungs can lead to mechanical pneumonia. Heat stress lowers immunity and increases vulnerability to disease. Sheep should be sheared at the beginning of the summer to help reduce the risk of heat stress in the months to follow.
Weather can have a tremendous impact on sheep breeding. Temperature and humidity play very important roles. High temperatures and humidity during the breeding season can reduce embryo survival, sperm quality and quantity. In addition, libido is reduced in both rams and ewes. Ewes show a decrease in behavioural estrus - this means that the ewes are cycling but they are not displaying the normal signs of estrus and are not likely to be breeding.
Moving and working cattle in hot humid weather can be a recipe for disaster. Minimize stress if you are working or moving cattle in hot humid conditions. If you must move them, let them choose their own pace and allow them to stop and graze as they go along. If they must be moved a long distance, calves can become overheated before they get there. If the herd is not slowed down or stopped for rest at the initial signs of heat stress, calves can become overheated to the point of death. Signs of heat stress in cattle include salivation and drooling, anxiety, high respiration and breathing with the mouth open. If they have access to water, they will stand in or near it but they won't eat. They simply spend their time trying to cool down.
Horses are also prone to heat stress. Young foals can overheat by simply standing in the hot sun. Ride in the early morning or evening when it is cooler. Horses that are not being worked can tolerate high temperatures and humidity fairly well. Activity and obesity increases the risk of overheating. The horse's primary cooling mechanism is sweating. Signs of heat stress in horses include lack of desire to play and eat, an increased heart rate, diarrhea and panting.
Animals with more fat or muscle, dark skin or a thick hair coat are more at risk when it comes to heat stress. Animals will eat less if they are too hot. If they are refusing to eat during the day, make sure they have access to grazing or some type of feed in the early morning or evening when it is cooler. If working or moving livestock is a must, do it in the cool part of the day. It may seem obvious, but providing fresh clean water during the summer is very important. Shade or shelter is also important. Animals must have some relief from the sun and heat.
For more information on this or other livestock related topics, please contact Jenifer Heyden, at 306-446-7961 or the Agriculture Knowledge Centre at 1-866-457-2377.
- Heyden is Regional Livestock Specialist, North Battleford Regional Services Branch
