Although the UK climate rarely feels “hot” by global standards, dairy cows can begin to experience heat stress at temperatures much lower than many farmers expect. In fact, once temperatures rise above about 20–22 °C, particularly when humidity is high, high-yielding cows can struggle to dissipate heat. The result is reduced feed intake, falling milk yield, poorer fertility, and increased risk of metabolic and health problems. Taking steps in spring can help reduce these impacts before the warmer months arrive.
One of the earliest signs of heat stress is a drop in dry matter intake. Cows will eat less in order to reduce metabolic heat production, which quickly translates into lost milk yield. In addition, heat-stressed cows spend more time standing and less time lying down, increasing the risk of lameness. Fertility is also affected: conception rates often fall and early embryo loss becomes more common during hot periods.
Simple management changes can make a significant difference. Water availability is critical: lactating cows may drink more than 100 litres per day in warm weather, so ensuring adequate trough space and fast refill rates is essential. Shade and ventilation are equally important. In housed systems, check that fans are clean, working effectively and positioned over feed barriers and cubicles where cows congregate. Improving airflow through buildings by opening sidewalls or removing obstructions can also help.
Feed management should not be overlooked. Pushing up feed more frequently and ensuring fresh feed is available during cooler parts of the day can encourage intake. In some cases, small adjustments to ration formulation to maintain energy intake are warranted.
The key message is that preparation should begin before temperatures rise. Reviewing housing ventilation, water supply, and cow comfort in April or May allows time to address problems. With increasingly warm summers becoming more common, proactive planning can help protect both cow welfare and farm profitability.
Written By Tom Shardlow, Veterinary Surgeon
