Why Are Dairy Cows Producing Less Milk in Extreme Heat? What Farmers Can Do

Heat stress can affect dairy animals before farmers notice a major fall in milk production. Higher temperatures can reduce feed intake, increase water requirements and affect reproduction. The National Dairy Development Board says heat stress can also reduce productivity and cause serious health problems in severe conditions.

The problem can be more serious for crossbred and exotic cattle and buffaloes. NDDB notes that indigenous cattle generally tolerate heat better, while buffaloes have fewer sweat glands and absorb more solar radiation because of their dark skin.

When an animal becomes overheated, it uses more energy to maintain its body temperature. Feed intake can fall, while water consumption increases. These changes reduce the nutrients available for milk production and can affect the animal’s overall condition.

NDDB cites studies showing that heat stress can reduce milk yield by 10% to 30% during first lactation and by 5% to 20% during second and third lactations. The actual effect varies with breed, environment and management.

Farmers may notice increased panting, sweating, water intake and a reduction in feed consumption when animals experience heat stress. Increased pulse rate and changes in behaviour can also occur as the animal tries to lose excess body heat. A fall in milk production can become another visible sign. Farmers should not wait for milk yield to decline before improving cooling and water access, especially during periods of high temperature and humidity.

Why is water so important?

Water helps dairy animals regulate body temperature and digest feed. NDDB recommends free access to clean drinking water throughout the day and notes that a healthy adult dairy animal normally needs substantial amounts of water. Requirements increase during hot weather. Water should also be placed where animals can drink comfortably without standing in direct sunlight. NDDB recommends providing drinking water under shade during heat stress, which can support cooling while animals drink.

NDDB’s guidance says a healthy normal cow may require about 100 litres of water during hot conditions. Another NDDB advisory gives a general requirement of 75–80 litres for an adult healthy animal, with higher needs during summer. The exact requirement varies with milk yield, feed, temperature, humidity, breed and body size. Farmers should therefore keep clean water available continuously instead of restricting access to a fixed daily quantity.

Yes. Direct sunlight increases the heat load on animals. NDDB recommends providing shade and says a thatched roof with adequate height can help. Agri-nets can also provide shade where suitable structures are available. Farmers should make sure the shelter has enough space and does not trap hot air. A shaded shed with poor ventilation can still become uncomfortable when temperatures rise, especially during the afternoon.

Why does ventilation matter?

Air movement helps remove heat from the animal’s surroundings. NDDB recommends increasing air circulation in covered sheds and using ceiling fans or blowers where electricity is available. Ventilation becomes particularly important when animals remain indoors for long periods.

The shed should allow air to move through the animal area without creating excessive exposure to hot winds. Farmers should also keep the floor and surrounding area clean to maintain better hygiene.

Water misting or sprinkling can help animals lose heat through evaporation. NDDB recommends misting and describes cooling systems that combine water spraying with fans or blowers to improve evaporation from the animal’s body. NDDB’s cooling guidance describes spraying water directly on animals for short periods at intervals, followed by air movement. Farmers using such systems should ensure that the shed remains adequately ventilated and does not become excessively humid.

Heat can reduce feed intake during the hottest part of the day. NDDB recommends offering feed during cooler periods such as morning, evening and night during heat stress conditions. Grazing can also be shifted towards cooler hours where the system allows. Farmers should avoid making sudden major changes to the ration. Any adjustment should maintain adequate energy, protein, fibre, minerals and other nutrients required for the animal’s production stage.

Does heat affect reproduction?

Yes. Heat stress can reduce reproductive performance in dairy animals. NDDB reports that high heat loads can affect conception and may influence the reproductive tract, developing embryos and semen quality. This means heat management matters even when farmers are mainly concerned about milk. A temporary heat problem can also affect breeding outcomes and future production if animals remain under stress.

Buffaloes can be particularly vulnerable to heat because their dark skin absorbs more solar radiation and they have fewer sweat glands than cattle. NDDB says their ability to dissipate heat through sweating is therefore more limited.

Farmers keeping buffaloes should pay close attention to shade, water access and cooling during hot conditions. Allowing animals to remain exposed to direct sunlight for long periods can increase their heat load.

Crossbred and exotic cattle can be more sensitive to heat stress than indigenous cattle. NDDB identifies this difference in heat tolerance and recommends management measures such as cooling, suitable housing, water availability and nutritional management.

Farmers should consider breed when planning summer management. A shed that appears adequate for one group of animals may not provide the same level of comfort for high-producing crossbred cows.

Can nutrition help during heat stress?

Heat stress reduces dry matter intake, which can lower the nutrients available for production. Farmers need to maintain a balanced ration while making sure animals have access to adequate water and suitable fodder.

NDDB recommends changes such as using good-quality green fodder when available, properly chaffing dry fodder and balancing the ration. The aim is to maintain nutrient intake even when animals eat less during hot periods.

NDDB has developed a supplement called Pashu Sheetvardhak for managing heat stress in dairy animals. Its published information says feeding it at 350 grams per animal per day improved milk yield by up to 11% and fat content by up to 7% in cows and buffaloes.

These figures come from NDDB’s reported product results and should not be treated as a guaranteed increase for every animal. Farmers should discuss any supplement with a veterinarian or animal nutrition expert before changing the ration.

What should farmers do first?

The first steps are simple: provide clean drinking water, create shade, improve ventilation and reduce exposure to peak afternoon heat. Feeding can be shifted towards cooler periods while maintaining a balanced ration.

Farmers should also watch for excessive panting, reduced feed intake, abnormal behaviour and falling milk yield. Early action can reduce the duration and severity of heat stress before it affects production and reproduction more seriously.

Heat stress is not only a summer comfort issue for dairy animals. It can affect feed intake, milk production, reproduction and animal health. The risk is higher for animals that are more sensitive to heat, including many crossbred cattle and buffaloes.

For farmers, the practical response starts with water, shade, ventilation and feeding management. Cooling systems can be added where feasible. The aim is to reduce the animal’s heat load before production begins to fall, rather than trying to recover milk yield after severe heat stress has already occurred.