Heat Stress in Dairy Cows and Its Effect on Milk Production

Cattle handle cold far better than heat. They naturally run a higher body temperature than people — roughly 101–102°F (38.5–39.1°C) — so warm, humid conditions affect them quickly. For many herds, heat stress begins once ambient temperatures climb past about 75–80°F (24–27°C), especially when humidity is high.

The Signs of Heat Stress

Heat-stressed cattle often show faster breathing, a raised body temperature, more sweating, reduced movement, and lower feed intake. Because they eat less and spend energy trying to cool down, the effects show up on the bottom line — most visibly as reduced milk yield, but also slower growth and weaker reproductive performance.

Why It Matters All Summer

Heat stress doesn’t have to be extreme to cost money. Even moderate, sustained heat across a summer can quietly lower productivity and increase the risk of health issues. That’s why climate control in the barn isn’t a luxury — it’s part of running a profitable operation.

How Airflow Helps

When natural wind is weak, mechanical airflow becomes essential. HVLS fans move a large, steady breeze across the whole barn, helping cool animals, improve ventilation, and keep bedding and deep-litter areas drier. Good airflow helps keep cattle calmer, more comfortable, and more productive through the hottest months.