Heat Stress in Livestock

What causes heat stress in livestock?

Animals shed heat through breathing, sweating (in species that sweat) and by losing warmth to cooler air. When air is hot and humid, they cannot shed heat quickly and body temperature rises. Extension heat stress guidance from several states points to the combination of heat, humidity, sun, lack of airflow and lack of water as the real risk.

Heavy coats, dark color, older or overweight animals, pregnant or nursing animals, and animals not used to the weather are more at risk. Sudden hot spells early in summer catch animals before they adapt.

Animals that are older, overweight, pregnant, nursing, or recovering from illness are more at risk, as are those in transport or crowded pens. Keep an eye on them first when a hot spell starts. Heat stress also lowers eating and can reduce milk, growth and egg laying, and it can affect breeding. These are signs worth noting and mentioning to your vet.

What are the warning signs?

Watch for fast or open-mouth breathing, drooling, standing apart from the group, reluctance to move, weakness, stumbling, reduced eating, and slobbering. Species differ, so ask your vet what normal looks like for yours and how to check temperature safely.

Heat stress can become an emergency. If an animal collapses, cannot stand, or seems confused, call your veterinarian immediately and move it to shade with airflow while you wait. Follow your vet's instructions on cooling, since cooling too hard or wrongly can cause other problems.

Take notes on what you see and when, because your vet will ask. A quick call early often prevents a worse emergency, so do not wait to see whether signs pass.

How do you provide shade and airflow?

Natural tree shade works well if it is big enough for all animals at once and airflow is good. Built shelters should have open sides and high roofs for air movement, because a closed hot barn can be worse than open sun. Crowding animals into small shade increases heat.

Check shelters on the hottest part of the day, not in the morning. Look for corners where air does not move and fix ventilation there. Electrical fans need safe wiring done by a qualified person.

Orient shelters to catch prevailing breezes if you can, and keep tall weeds from blocking airflow along fence lines. Light-colored roofs and insulated roofs reduce heat under the shelter, so ask your extension office what works for your building.

How much water do animals need?

Water needs rise sharply in heat. Provide clean, cool, easy-to-reach water in more than one spot so shy animals can drink. Check troughs more than once a day, scrub algae, and place them in shade so water stays cooler.

Measure what your herd or flock drinks over a few days by tracking how often you refill, and plan storage in case a pump or line fails. Ask your vet whether electrolyte or mineral support makes sense for your animals instead of adding anything on your own.

Poultry, rabbits and pigs have their own heat needs and limits, so ask your vet or extension agent for species-specific guidance. Some animals cannot cool themselves well and rely on you for shade, ventilation and water.

How should you change management in hot weather?

Move work like hauling, worming appointments, shearing decisions, vaccinations, and trailering to the coolest hours or other days, and avoid crowding animals in pens or chutes. Transport is a time of high risk, so load with plenty of airflow and avoid midday.

Adjust feeding times so animals eat in cooler hours, and watch for animals that stop eating. Keep pasture from being grazed too short, since tall grass provides some cooling and shade.

Wet animals in humid weather cool poorly, so do not rely on sprinklers or wet-downs unless your vet or extension agent says they suit your species and your air. Misting in still humid air can add to the problem.

What should you plan before summer?

Walk your farm now and ask where animals would go if the heat hit tomorrow. Fix gaps in shade, add water points, trim brush that blocks airflow, and write down your vet's emergency number. Heat-related losses are often preventable with a few simple changes.

Costs fall into categories: shade structures or shade cloth, extra water troughs, hoses and storage, fans and wiring by a qualified person, and vet consultation. Start with water and shade, which help most.

Keep a short written heat plan on the barn wall: who checks water and when, which animals get checked first, who to call, and which tasks get moved to cooler hours. A written plan helps whoever is covering for you.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.