ENVIRONMENT is the determining factor in production and reproduction of livestock all over the world. Out of the environmental factors temperature and humidity have their prime effect on animal physiology, behaviour and productivity. In the coming months, the fury of blistering sun will rage unabated and mercury is likely to touch 45°C at some places in Pakistan and later during July and August such an increase may be seen for humidity. Higher ambient temperature and humidity is conductive to low feed intake, low milk production, reproductive failures and embryonic mortality, generally in dairy animals and especially in buffaloes.

The ideal ambient temperature for a temperate dairy cattle breed is between 41°F (lower critical temperature) and 75°F (upper critical temperature). At temperatures above 80°F, cows have to use energy to cool themselves through heat loss via surface skin and the respiratory tract.

As ambient temperature increases, it becomes more difficult for a dairy cow or a buffalo to cool herself adequately. However, this range is quite higher for our native cattle and buffalo. Sahiwal cattle and Nili-Ravi buffalo are naturally adaptive to higher temperature and humidity. These animals show the thermal stress sign when mercury starts touching to more than 100°F.

However, buffalo, the main contributor to total milk production (above 70 per cent of the total milk production) in Pakistan is more prone to thermal stress than native cattle breeds. For instance, buffaloes suffer if forced to remain, even for a few hours, in direct sunlight.

Body temperatures of buffaloes are actually lower than those of cattle, but buffalo skin is usually black and heat absorbent and only sparsely protected by hair. Also, buffalo skin has one-sixth the density of sweat glands that cattle skin has, so buffaloes dissipate heat poorly by sweating. Under hot conditions, buffalo’s body temperature, pulse rate, respiration rate, and general discomfort increase more quickly than those of cattle.

However, high humidity seems to affect buffaloes less than cattle. In fact, if shade or wallows are available, buffaloes may be superior to cattle in humid conditions. The most common index of heat stress (temperature-humidity index or THI) is calculated from the temperature and relative humidity (RH). Dairy animals begin to suffer more whenever they are exposed to higher THI than merely to high temperature or RH.

Heat stress has its direct association with difficult births, heat exhaustion, fatty liver in fresh cows and buffaloes, and mastitis, as well as adverse reactions to vaccinations leading to abortions and death. High producing cows are the animals most sensitive to heat stress because of their high feed intake. Dry matter intake starts to drop (10-22 per cent) and milk production losses of 20-35 per cent, when temperature exceeds from upper critical temperature range of lactating animal.

Heat stress can contribute to lameness, perhaps due to acidosis or increased output of bicarbonate. Heat stressed cattle and buffalo eat less frequently and feed during cooler times of the day, but they eat more at each feeding. Reduced feed intake followed by slug feeding when the temperature cools down, can cause acidosis, which is considered a major cause of laminitis.

As ambient temperatures rise, the respiratory rate increases with panting progressing to open-mouth breathing especially in temperate cattle. A consequence is respiratory alkalosis resulting from a rapid loss of carbon dioxide. The cow/buffalo compensate by increasing urinary output of bicarbonate, and rumen buffering is affected by decreased salivary bicarbonate pool. Lameness, with sole ulcers and white line disease, will appear in a few weeks to a few months after the heat stress occurs.

These losses are apparent in the decreased amount of milk shipped; increased days open, and decreased breeding per conception both in cattle and buffalo. Such adverse effects on dairy animal’s productivity can be minimized if certain management and nutritional strategies are followed during summer months.

To reduce heat stress in dairy cattle and buffaloes requires a multi-disciplinary approach. It should include breeding, nutrition, structural design of the shed, environmental controls, and management. Following management practices and nutritional strategies are necessary to have better productive and reproductive efficiency in dairy animals during summer months.

Regular supply of clean-cool drinking water is needed for better dairy performance during summer months. Cows and buffaloes need to increase water intake during times of heat stress to dissipate heat through the lungs (respiration) and by sweating. Water consumption by dairy animals increase about 60 per cent during summer. If water supplies are not adequate, heat stress becomes severe; cows divert water normally used in milk synthesis to the metabolic processes of heat dissipation. The automatic watering systems may be quite helpful for water provision to dairy animals.

If such arrangements are not possible then at least, 4-5 times, clean drinking water should be supplied to dairy animals. Water should be present under shade and enough space should be ensured. Showering/splashing of water on the body thrice a day decreases the heat stress in buffaloes.

Buffaloes are found to response more quickly to cooling devices than cows. Such practices increase the feed intake, milk yield and conception rate in buffaloes. Wallowing is the cheapest and least laborious device to beat the heat in summer. Buffaloes are made to wallow in clusters in ponds, stream, rivers, tanks or other water bodies for hours together. Wallowing is an important route of heat loss in view of the labile body temperature, which enables the animal to store body temperature.

In shade or in a wallow buffaloes cool off quickly, perhaps because a black skin rich in blood vessels conducts and radiates heat efficiently. Wallowing becomes more effective if buffaloes remain in shade after getting out of water.

A dairy barn with proper facilities for tying, feeding, watering, grooming and showering should be preferred. It should be possible to reduce the maximum ambient temperature in about depress which may give comfort to the inmates of the shed. This can be possible by covering doors and windows with fibre mating, which should be kept ever wet with continuous percolation of water during day time. Fans need to be provided to ensure air circulation inside the shed.

If cows are to be confined under a shade structure, it should be oriented with a south-eastern exposure of an open sidewall. Walls of free stall barns should be opened up to maximize air movement. Eliminate any wind block within 50ft of the windward side of the building. Each cow should be provided with 60sqft of shade. Earthen floors under shades quickly can become mud holes and thus are not generally recommended.

Evaporative cooling methods include mist, fog, and sprinkling systems. Open sided barns with raised roof (12ft) having fans and foggers arrangements are the most feasible for dairy buffaloes. A mist or fog system sprays small water droplets into the air and cools the air as the droplets evaporate. When an animal inhales the cooled air it can exchange heat with the air and remove heat from its body. High-pressure foggers disperse a very fine water droplet, which quickly evaporates and cools the air while raising the RH.

As fog droplets are emitted, they are immediately dispersed into the fan’s air stream where they soon evaporate. A ring of fog nozzles is attached to exhaust side of fan. Cooled air is blown over animal’s body. Foggers should operate during daylight hours only; humidity is too high at night but fans should operate continuously.

Shady trees should be planted on the dairy farms that protect the animals from scorching sun. Dairy animals in loose housing with a shade (may be shed) for feeding and shelter during the inclement weather and open area for night hours produce more milk.

During summer, cattle and buffaloes in heat should be inseminated with frozen semen processed during cooler months. To detect silent heat, teasers with extraordinary libido need to be paraded. The buffalo teasers with poor libido usually fail to detect silent heat in summer months. Such steps can break the breeding seasonality in buffaloes.

Flies can contribute to heat stress. Eliminate fly breeding areas on a weekly basis, including manure, wet spilled feed, manure drains, and leaking water cups. Commercial preparations can be used to spray on feeders or applied to animals for fly control during summer months.

Nutritional and feeding modification can help minimize the drop in milk yield summer causes. Decreasing the forage to concentrate ratio (feeding lees forage and more concentrate) can provide animal with more digestible nutrients and thus increase the intake.

Feed additives like yeast that enhanced the fibre digestibility include the fungal cultures and niacin that improved the energy utilization can be used in the dairy ration during hot weather. However, all of these additives would not usually be used together.

Fat is a cold nutrient (yield more metabolic water on hydrolysis in animal body) and has higher energy value can be added in the dairy ration to improve energy intake. Whole oil seeds (cottonseeds or soybeans), tallow, rumen inert sources, or combinations can be used for fat provision in dairy diets. Dairy mixes usually contain about three per cent fat contents from oil seed meals and other vegetable sources. Ruminally inert fat could be supplemented in dairy diets up to four per cent during summer.

In Pakistan where the high fibre diets are being fed to dairy animal, the tallow or crude vegetable oils could be supplemented up to six per cent in the dairy rations. Because fatty acids reduce the intestinal absorption of calcium and magnesium, requirements for these two minerals increase when fats are fed. Supply 0.85 per cent calcium and 0.30 per cent magnesium in the ration when fats are fed.

Overfeeding of crude protein (especially from non-protein nitrogen) during hot weather should be avoided because it takes energy to excrete excess nitrogen. Dairy rations should not contain more than 16 per cent crude protein on a dry basis during summer months. It is better to provide about 60 per cent of the total crude protein as ruminally un-degradable. The oil seed meals (canola seed meal, cotton seed meal and soybean meal), corn and wheat gluten could be used to improve ruminally un-degradable protein contents in dairy ration.

Hot weather increases the need for certain minerals because that increased sweating and urination resulting in more minerals being excreted. Potassium should be increased to at least 1.4 percent of dry matter, sodium to 0.40 per cent, and magnesium to 0.30 per cent. Magnesium may be increased already if fats are being fed.

Some things that good managers can consider when feeding lactating dairy cattle during hot weather are total mixed rations (forage plus concentrate), feeding frequency (an extra feeding or two), time of feeding (cooler time of day), adequate feed bunk space (all cows/buffaloes can eat together without crowding), plenty of cool water, and adequate air flow. Keeping cows comfortable is the key to keeping them eating which is critical in keeping them productive under scorch.

(The writer is s post-doctorate fellow at the National Livestock Research Institute, Korea)