Heat stress in sheep

الإجهاد الحراري في الأغنام - Shopivet.com
Sheep may be exposed to some climatic changes that may cause significant economic losses, the most important of which is heat stress, which occurs significantly in the summer periods, as air temperatures and humidity increase, and this is what we see and increases every year from the previous one due to climate changes that help in the occurrence of that.
There are some factors that may increase the effect of heat stress on sheep flocks, as follows:
environmental factors:
  • The ambient temperature, which is higher than the body temperature of sheep, which reduces the animal's ability to lose heat.
  • Relative humidity, we find that increased humidity reduces the animal's ability to lose heat through evaporation by approaching (panting).
  • Solar radiation: The heat generated by solar radiation can greatly exceed the metabolic heat produced by an animal.
  • Wind speed, heat stress increases in calm air conditions because convective heat loss decreases dramatically.
  • Nighttime temperature High nighttime temperatures prevent the loss of heat gained during the day, increasing the risk of heat stress.
animal factors:
  • Wool: Wool gives adequate protection from heat only when the wool reaches 3-4 centimeters in length.
  • Breeds originating from cold regions are more susceptible to heat stress.
  • Of age, lambs are very susceptible to heat stress due to their higher metabolic heat production, and higher natural respiration rate.
  • During pregnancy, the increase in metabolic heat production during late pregnancy can predispose ewes to increased heat stress. 
Symptoms of heat stress:
  • Increased body temperature and respiratory rate are among the most important signs of heat stress in sheep. With a marked decrease in feeding rates
  • Seeking shade, low dry matter intake, crowding around water troughs and lethargy.
  • Excessive heat stress may cause a decrease in natural immunity, which makes animals more susceptible to diseases, loss of some mineral salts from the body, lower quality of meat, and ultimately huge economic losses resulting from increased mortality and a decrease in the general performance of animals.
Methods of prevention of the effects of heat stress on flocks of sheep:
  • It is preferable not to expose animals to sunlight or high temperatures, so that the animals go out to graze in the early morning, as well as in the evening period, after the sharpness of the temperature of the surrounding environment has subsided.
  • Taking into account the good shading of the farm to protect the animals from the sun.
  • The food feeders and drinking troughs should be in the shaded part of the farm.
  • Group treatments and immunizations should be conducted in the evening to reduce stress on animals.
  • Fans should be spread on the farm, as well as fans equipped with water mist, and they should be at specific times, especially during the increase in temperatures.
  • The need for the process of shearing wool (shearing wool) to be done at a rate of twice a year, so that the first time is before the summer, with a sufficient period for the wool to grow to a degree that helps protect from the heat of the surrounding environment. Therefore, it is preferable to be in the spring, specifically in the month of March. The second time is in the fall season, specifically in the month of September, in order to allow the growth of wool to the degree that protects the animal from the cold weather in the winter season.
  • Availability of clean drinking water constantly and some ice can be put in the water for cooling before serving it to the animals.
  • Reducing the concentrated ration and focusing on the green ration, and the concentrated ration is in the evening period.
  • It is preferable to add vitamins to drinking water, especially vitamin C (C), because of its role in relieving heat stress.
  • The need to add mineral salts to drinking water to compensate for the loss of mineral salts that occur as a result of heat stress.

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