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Managing Heat Tolerance in Cattle

Heat stress costs weight gain, fertility and sometimes animals. Selecting for adaptation helps, but day-to-day management matters just as much.

What heat stress looks like

Cattle that are too hot breathe faster, may drool or hold their mouths open, stand apart from the herd or crowd into shade, and eat less. Severe heat stress can be life threatening. Learn what normal looks like for your cattle so changes stand out.

Humidity makes things worse because cattle cool less effectively. Hot, still, humid days and warm nights without relief are the hardest on them.

Dark-hided cattle absorb more heat from the sun than light-colored ones, and cattle with thick winter coats that have not shed are at risk. Watch these animals first in a heat wave. Make a heat plan before summer starts, so that shade, water and working schedules are settled before the first hot week.

• Fast, heavy breathing or panting
• Drooling or open mouth breathing
• Bunching in shade or around water
• Reduced feed intake
• Reluctance to move

Water comes first

Cattle drink much more in hot weather. Make sure every pasture has clean water in enough volume and enough access points so that cows are not fighting for a turn. Check tanks, floats and pipes often during hot spells.

Clean tanks regularly, because warm water grows algae and gets less appealing. If animals avoid a tank, find out why.

Make a habit of walking every water source each morning during summer. A tank that failed overnight can mean thirsty cattle by midday. Check water pressure and flow rate as well as level. A trickle that cannot keep up in the afternoon is a hidden problem.

Shade and airflow

Natural shade from trees works well when there is enough of it. Artificial shade structures can help where trees are scarce. Airflow matters too, so avoid crowded pens with no breeze.

Plan shade and water near each other so cattle do not have to travel far in the heat.

Windbreaks that block summer breezes can hurt as much as they help in winter. Think about where the airflow runs before you build or plant. Cattle that cannot reach shade will stand in water or crowd each other, so give them room to spread out.

Handling cattle in hot weather

Work cattle early in the day, keep sessions short and avoid pushing animals hard. Heavily muscled cattle and animals already stressed are at higher risk. If it is too hot, postpone the work.

Do not leave cattle crowded in a pen or trailer. Ask your veterinarian or extension office for guidance on handling plans for hot weather.

When trucking cattle in hot weather, avoid loading at midday and avoid crowded loads. Ask your hauler about plans for stops and ventilation.

Feeding in the heat

Feed intake falls in the heat, and the heat generated while digesting forage adds to the load. Talk to a nutritionist about timing and ration changes during hot weather. Do not make sudden changes without advice.

Provide mineral supplements suited to your area and ensure forage quality is good.

Keep mineral and salt available and clean. Ask your nutritionist whether any changes to your mineral program make sense during hot spells. Keep an eye on feed quality, since poor forage generates more heat during digestion and adds to the load.

Breeding for heat adaptation

Breeds and crosses differ in how they cope with heat, humidity and insects, and so do individuals within a breed. Coat type, color and skin are among the traits that affect tolerance. Fertility in hot weather matters too, particularly bull fertility.

If you are choosing bulls for hot country, ask the breeder how the herd performs in conditions like yours. Ask your extension office what has worked in your area.

Bulls are especially important. Heat can reduce semen quality for some weeks, so ask your veterinarian about checking bulls before the breeding season in hot country.

Common mistakes and when to call the vet

Waiting to act until cattle are in distress, working cattle at midday and letting water run short are the usual problems. Another is assuming a heat-adapted breed needs no help.

Call your veterinarian if cattle show severe signs of heat stress, collapse or fail to recover once cooled. Any treatment must follow your vet's directions and any withdrawal times.

• Check water systems daily in hot spells
• Provide shade near water
• Work cattle at cooler times
• Call the vet for severe cases

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