Pashu Sandesh, 30th June 2020

Neela Madhav Patnaik1, Parag Acharya2, Bibhudatta Samanta Panda3, Sunil Kumar Mohapatra4, Arghyadeep Das5


Global warming has a great negative impact on the reproductive performance of cattle and buffaloes. Climate change has resulted in droughts, due to which feed and water scarcity are seen in the case of grazing animals. The effects of climate change will also influence pasture resource depletion, thus depriving grazing animals of nutrient requirements. These conditions aggravate the decrease in growth and reproductive efficiency in livestock. Generally, the impact of hot weather has been referred to as heat stress. Heat stress can be defined as the point where the animal cannot dissipate an adequate quantity of heat to maintain body thermal balance. Climatic factors that may influence the degree of heat stress which include: temperature, humidity, radiation and wind. In India, the summer temperature goes beyond 450C which is 180 C above the upper critical temperature of dairy cattle. When the temperature exceeds 270 C even with low humidity, this temperature is above the comfort zone for the high producing dairy cows. All the changes associated with heat stress lead to loss of productivity reduced breeding efficiency and even loss of life in extreme cases. Every year in India severe loss in milk production is incurred due to heat stress causing huge economic loss to dairy farmers. Heat stress also has detrimental effects on reproduction by decreasing oestrus expression, conception rate and by increasing length of service, dry period and calving interval. Though indigenous breeds of cattle are more thermo-tolerant, crossbred and exotic breeds of cattle are highly sensitive to heat stress. Buffaloes are more prone to this owing to their black skin that absorbs more solar radiations. Understanding the cause of heat stress and management strategies are particularly important so as to save the farmers from financial distress.


  • Heat stress occurs when an animal's heat load is greater than its capacity to lose heat
  • High air temperature, humidity, solar radiation and low air movement contribute to increased risk
  • High relative humidity decreases evaporation and reduces the cow's ability to lose heat by sweating and breathing
  • When the air temperature is greater than about 21ºC and relative humidity is greater than 70%, Friesians and crossbreeds begin to reduce their feed intake, and milk production is reduced. Jerseys are more tolerant of heat, with production losses insignificant until 25ºC
  • Cows radiate heat during the night to the cooler surroundings. Warm cloudy nights can reduce cooling, increasing the risk of heat stress



  • Heat stress increases: Respiration Rate, Rectal Temperature, Water Intake, and Sweating
  • Heat stress decreases: Rate of Feed Passage, Dry Matter Intake, Blood Flow to Internal Organs, Milk Production, and Reproductive Performance
  • Heat stress leads to acidosis through Panting and loss of CO2, Decreased rumination, Drooling and loss of salivary buffer (bicarbonate)


Common symptoms of heat-stressed animal include:-

  • Seek out the shade, and may not leave to drink/eat
  • Water intake enhanced while feed intake reduced
  • Prefers standing than lying down
  • Increased production of saliva
  • Open-mouth panting
  • Rapid and weak pulse
  • Rapid but shallow breathing
  • Unusual salivation
  • Dizziness/unconsciousness
  • Skin becomes dull and maybe cold too


  1. Shed with its long axis running East-West provides a cooler environment than one with a North-South orientation
  2. Open type of sheds has an advantage over closed type shed
  3. Minimum roof height should be 10.0 feet to reduce heat load. The height of shelter in a hot climate should be between 3.0 - 5.0 m
  4. Points to be considered while feeding animals during hot weather, as feeding frequency, (extra feeding) time of feeding, (cooler time of a day, adequate feeding space and plenty of cool water
  5. Use of water as a cooling agent either directly on an animal body or for cooling the shelter microenvironment is as a widely accepted practice. Water can be used for spraying the floor and roof of shelter periodically or continuously during peak hot hours which lower their temperature
  6. Plantation around the farm will help in alleviating heat load from the animals. But, in today’s commercial dairy industry, it is not always practicable. Therefore, provision of artificial shade area by a shade cloth or a naturally well-ventilated structure with open sidewalls can keep the animals away from direct solar radiation
  7. Restrict handling to early morning and late evening as the stress and physical activity of handling livestock during the hotter parts of the day will increase animals’ body temperature
  8. Ensure that the animals are kept under shades. The most effective source of shade is trees. If shade trees are not available, the thatched roof of a minimum height of 9 feet should be provided
  9. The most effective way of combating heat stress in buffalo is wallowing in the water pond
  10. Prefer grazing during early morning & late evening hours to avoid the scorching heat


Preventing heat stress will help maintain higher milk production, better reproduction, improve animal health through reducing chances of acidosis and lameness, and improve animal well-being. Environmental management is a very important skill for farmers to hone. Although we cannot control the weather, we certainly can control the areas our cows inhabit to help prevent potential disasters in the heat of summer.

Neela Madhav Patnaik1, Parag Acharya2, Bibhudatta Samanta Panda3, Sunil Kumar Mohapatra4, Arghyadeep Das5

1*Ph.D. Scholar, Dairy Extension Division, NDRI, Karnal

2Asst. Prof., Livestock Production and Management, College of Veterinary Science, Rampura Phul, GADVASU, Ludhiana

3Ph.D. Scholar, Animal Physiology Division, NDRI, Karnal

4Ph.D. Scholar, Animal Biochemistry Division, NDRI, Karnal

5Ph.D. Scholar, Dairy Economics, Statistics and Management Division, NDRI, Karnal

Corresponding Author-