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Heat stress is one of the most underestimated challenges in dairy production. As temperature and humidity rise, high-yielding cows struggle to shed the metabolic heat generated by digestion and milk synthesis. The result is lower feed intake, reduced milk yield, poorer fertility and a higher risk of metabolic disease — often before producers realise the herd is affected.

Recognising the signs

Cows experiencing heat stress eat less, pant, drink more, and spend more time standing to increase their surface area for cooling. Milk yield drops, milk components change, and conception rates decline in the weeks that follow. Because these effects build gradually, monitoring the temperature-humidity index is a valuable early-warning tool.

Cooling and nutrition go together

Effective heat-stress management combines physical cooling with nutritional support. Shade, ventilation, fans and water sprinklers help cows dissipate heat, while dietary adjustments compensate for reduced intake and the loss of electrolytes through sweat and panting.

• Provide abundant shade and clean, cool drinking water at all times
• Use fans and sprinklers to cool cows, especially in the holding pen
• Adjust rations to maintain energy intake when appetite falls
• Support electrolyte and mineral balance during hot periods
• Schedule feeding and handling for the cooler parts of the day

Cows lose the most to heat stress in the days you are not yet thinking about it. Prepare before the heat arrives.

VPhS Technical Team

Conclusion

Protecting dairy cattle from heat stress requires a proactive, combined approach: physical cooling, targeted nutrition and thoughtful management of the daily routine. Acting before temperatures peak preserves milk yield, safeguards fertility and keeps cows healthy through the warmest months.