Management Of Heat Stress In Dairy Cattle
Femi FrancisaAshutoshb, Kantac, ManjuAshutoshband Kavitac
aMVSc Scholar, Division of Animal Physiology, National Dairy Research Institute, Karnal, Haryana, India
bSenior scientist, Division of Animal Physiology, National Dairy Research Institute, Karnal, Haryana, India
cSRF, Division of Animal Physiology, National Dairy Research Institute, Karnal, Haryana, India
Email: femi285685@gmail.com
Heat stress is a natural phenomenon affecting dairy cows and other domestic animals in tropical and sub-tropical regions of the world during the summer months. During summers heat and high humidity combine to make an uncomfortable environment for the dairy cows. In the present scenario of climate change the intensity of heat stress affecting the animal is alarming. Now, heat stress becomes one of the chief problems in the dairy sector resulting in decreased production and fertility during summers.
Symptoms of the heat stress
The ideal temperature range for the dairy cattle for efficient production is between 0-22°C known as the thermoneutral zone. When the temperature of the environment rises above the thermoneutral zone (combined with humidity), the dairy cattle start showing symptoms of heat stress. High yielding exotic cows exhibit more symptoms of heat stress when compared to low yielding indigenous cows as high yielding cows generates more heat as they consumes more feed for higher production. The major symptom elicited by the heat stressed dairy cattle is the reduction in the feed intake. During times of heat stress, feed intake is reduced by 8 to 12 percent in dairy cattle. The reduction in the feed intake by the cattle results in decreased production of the volatile fatty acid in the rumen, which may lead to acidosis and reduced fat content of the milk.
The heat stressed dairy cattle elicits various behavioural responses to reduce the heat load on them.Shade seeking is important amongst the behavioural signs during heat stress. Dairy cows choose to stand in the shadesof the tree for a longer period of time instead of lying in warm conditions. They prefer standing over lying down in summer as more skin surface get exposed for air flow thus resulting in heat loss. It also helps to reduce the heat gain into the body from ground through conduction. Unshaded cattle adopt other behavioral strategies such as increasing time around the water trough. Cattle spend more time around the water trough because evaporation from the trough generate a cooler microclimate, compared the rest of the enclosure. Dairy cattle changes its body’s orientation to sun such that the incident radiation from the sun is less and thus trying to reduce the heat load on the animal.
Other important signs occasionedduring heat stress include increased water intake in order to maintain the water balance of the body as small quantities of water is lost through evaporation. At higher levels of heat stress, the dairy cattle show open mouth-panting and increased respiratory rate. These may results in loss of water from the body hence the heat stressed cattle have increased water intakes.
Consequences of heat Stress
Heat stress has deleterious effectson a variety of dairy parameters including milk yield and reproduction,hence a significant financial burden to the dairy farmers. In an attempt to reduce heat stress animal decreases feed intake which leads to less favorable rumen environment and function, lower volatile fatty acids (VFA) production, microbial protein production and nutrients digestibility. As a consequence of heat stress, significant reduction in milk yield occurs. Milk yield decreases by 10-15% and 40-50% in well-cooled and non-cooled management systems during severe heat stress conditions.
Recent studies have reported that heat stress during the dry period impairs mammary gland development and alters metabolism in dry and transition cow, which in turn, reduces milk yield in subsequent lactation even after cows have returned to more comfortable environmental conditions after calving. Heat stress also negatively affects fertility and reproduction of dairy cattle. Studies on the success of “Artificial Insemination” during heat stress have indicated only 10 to 20 % of inseminations in “heat stressed” cows resulted in pregnancies.
Methods to alleviate heat stress
Different strategies can be used in a dairy farm to alleviate or to reduce heat load on cattle. To reduce the heat stress, it is vital to keep cows as comfortable as possible, which maximizes dry matter intake and optimizes milk yield. Providing adequate amounts of clean and fresh water is one among the major strategy to reduce heat stress.During heat stress cattle consumes twice or thrice the amount of normal drinking water.
Providing shade at the shed will help the cows to deal with warm weather. Cooling of the dairy farm can be done using commercial coolers, tunnel ventilation, shower/fanning stations, fans, and cooling ponds. Usage of cooling fans in the cattle shed is the most reliable method to reduce the heat stress imposed on the animal. Fans remove the body heat via convection, thereby cooling down the surface of the animal. Sprinklers are used in some of the dairy farms as sprinkling of the water to the hair coat helps in reducing the body heat through conduction. Sprinkling of water on the thatched roof of the shed will also results in reduced atmospheric temperature inside the shed thereby reducing thermal stress on cattle.
Ration modification of dairy cattle can also be done during summers to reduce the heat stress. To increase the energy intake of the animal, supplemental fat can be added to the ration. The high-fat feeds such as whole cottonseed tallow or bypass fat, roasted soybeans etc can be added to the ration. Low fibre diets are often preferred over high fiber feedstuffs as it results in less heat increments. Diets high in grain and low in fiber must be included in the rations because of the lower heat of digestion. Feeding buffers such as sodium bicarbonate and magnesium oxide allow higher concentrate rations to be fed and help in alleviating the low-fat milk syndrome during heat stress due to reduced feed intake. Supplementation of minerals in feed can be done at times of heat stress as there is increase in the loss of minerals through increased sweating and urination.
Conclusion
Dairy cattle should be kept in optimum environmental temperatures during summers to make them more comfortable and productive. Providing shades and adequate amounts of water to cattle along with ration modification can reduce the heat stress. Normal reproductive capacity and milk production of the cattle can be maintained during summers if proper heat alleviation methods are used.
References
1. Heat stress in Dairy cows (2015).Nutriad.https://nutriad.com/2015/08/heat-stress-in-dairy-cows/.
2. Gerald, M. J.and Charles C. S.(1999).Reducing heat stress for dairy cattle.Virginia Cooperative Extension, Dairy, 404-200.
3. Jodie A. P. and Devender, K.V. (2011). Heat stress in dairy cows.http://articles.extension.org/pages/11047/heat-stress-in-dairy-cattle.
4. Stephen C. N. (2014).Management strategies to reduce heat stress, prevent mastitis and improve milk quality in dairy cows and heifers. UGA,Extension Bulletin, 1426.
Source: Sadana Publishers India, Dairy In India, Year Book,
This Article is for the benefit of dairy farmers and persons rearing dairy animals.
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