Heat Stress in Livestock

Animals feel stress differently than humans. Because most animals do not have sweat glands, they are unable to cool themselves through the evaporation of sweat on their skin.

Instead, animals will try and wade in water, or breathe heavily (also called panting) in order to release added heat in their bodies.
When animals are under heat stress, they can stop eating, decrease in weight, stop milk or egg production and may not be able to reproduce.
Animals under heat stress also consume large amounts of water, an added expense for farmers.

Source: Recognizing Heat Stress | USDA