Managing Heat Stress in Sheep and Goats

Many animals die from extreme heat and humidity each year.

“Extreme heat is stressful to livestock, including sheep and goats,” said David Brown, University of Missouri small ruminant specialist. “It is very dangerous if the onset of heat is sudden and animals do not have ample time to adapt.”

In Missouri, the heat index recently peaked at 117 F. Brown says heat index gives a more accurate measure of heat stress than temperature alone because it combines temperature and humidity.

“The record-breaking heat has had a direct impact on sheep and goats,” said Brown. “Heat stress affects performance of the animals by decreasing feed intake. Reduced feed intake impairs production, reproduction, growth, milk quantity and quality and lowers immunity to diseases. Although sheep and goats are less susceptible to heat stress than other livestock species, long-term exposure might have devastating effects. Animals may reach a point where they cannot dissipate an adequate quantity of heat to maintain body thermal balance.”

When extreme heat waves hit the state, producers should take adequate measures to combat heat stress in their livestock. Heat stress is considered severe in sheep and goats when the temperature humidity index (THI) is between 84 and 86 F; a THI above 86 F is considered extreme.

“Producers should adopt a multidisciplinary approach to lessen the impact of high heat and humidity,” said Brown. Consider these strategies:

• Providing access to plenty of clean, cool water is extremely important during hot weather. On average, sheep or goats will drink 1-2 gallons of water per day. Lactating animals will drink more. A research report from University of Maryland Extension showed that sheep drink 12 times more water when it is dry and the temperature exceeds 100 F.

• Sheep should not be sheared in extreme heat. A thick fleece acts as insulation against temperature changes. It has been documented that sheep with a 1-inch fleece tolerated higher temperatures than sheep with less wool.

• Livestock should not graze during the heat of the day. Encourage early morning or late evening grazing to maintain normal feed intake.

• Provide nutrient-dense diets during periods of high heat and/or humidity. Less body heat is produced when livestock are fed grain rather than poor-quality forages. Feed additives such as live yeast and vitamins C and E are essential to offset the impact of heat stress.

• Provide shade in the form of Quonset huts, polydomes or carports. Mature trees are a low-cost option and provide excellent shade and shelter for grazing animals. When livestock are housed in barns, an evaporative cooling system with water in the form of mist or sprinkling is recommended, but do not let these areas become extremely wet and muddy.

• Monitor for signs of distress. Clinical signs of heat stress include continual panting, rapid breathing, weakness, inability to stand and rectal temperature over 105 F. Death may occur with a rectal temperature over 107 F as the animal’s cells begin to degenerate.