Kelly Froehlich, Assistant Professor and South Dakota State University Extension Sheep Specialist
(Previously published with South Dakota State University Extension: November 18, 2021)
The Upper Midwest provides periods of extreme heat during summer and shorter periods of heat stress potential during spring and fall. Are your sheep and goats cool enough in their environment? Heat stress affects sheep and goat performance by decreasing dry matter intake, while increasing the need for water. This, in return, has a direct impact on weight gain and milk production. Although sheep and goats are more heat-tolerant than other ruminants (e.g. cows), it is important to understand and identify when they may be experiencing stress.
Understanding Heat Stress
Several factors contribute to whether a sheep or goat will experience heat stress, including breed, relative humidity, temperature, wind speed, and solar radiation. The comfort zone of a fully fleeced sheep is about 10 to 90°F; this is where heat produced is the same as heat lost. Temperature comfort zone is less defined in goats, but it is generally accepted that they are better adapted to hot conditions. However, temperature is only part of the equation, with humidity having a huge impact on whether an animal will feel cool or heat stressed. Therefore, temperature humidity index (THI) is the best measure of livestock environmental stress (Table 1). Specifically for sheep and goats, heat stress is experienced when Continue reading