By-Dr. Arjun singh, Dairy consultant.
In India, the summer temperature goes beyond 45 C which is 18 C above the upper critical temperature of dairy cattle.
When the temperature exceeds 27 C even with low humidity, the
temperature
is above the comfort zone for the high producing dairy cows.Humidity plays
significant role in heat stress.
The most common index of heat stress is calculated from the temperature and relative humidity(RH).
At high ambient temperature the animals waste their feed energy in Panting and Sweating the nature ‘s way of cooling animals by evaporation.
During summer the milk production is reduced to the extent of 50%.
The crossbred / exotic animals are more prone to the heat stress losses as compared to indigenous cattle.
Animals during heat stress.
(a) Reduced feed intake
(b) Increase water intake
(c) Change in the metabolic rate /maintenance.
There are several factors , which influence the severity of heat stress. These include
1.Environmental condition
2.Level of production & feed consumed
3.Stage of lactation
4.Cooling management.
5.Exercise requirements
6.Breed and Body colour
All these factor influence heat production, degree of stress she is subjected to and how effectively the low dissipate heat. These factors collectively get reflected in milk reflected in reduction in milk yield and reproduction efficiency. This productivity loss during summer can be reduced substantially by adopting the following heat stress management coupled with good health management.
(A) Proper summer oriented housing
(B) Animal cooling system(Sprinkler and or fogger)
(C) Development of breeds tolerant to heat stress
(D) High energy feeding
(E) Swimming pool
Feeding and nutritional management—–
Points to be consider while feeding animals during like “Dairy cooler feed”hot weather, as feeding frequency, (extra feeding) time of feeding, (cooler time of a day, adequate feeding
space and plenty of cool water. Modification in ration can help to minimize the drop in milk production,decreasing concentrate to forage ratio, with more moisture content to combat heat stress and result in more digestible rations. Feeding buffers such as sodium bicarbonate and magnesium oxide allow higher concentrate rations and can help in low fat milk syndrome also. Hot weather increases the need of certain minerals. Do not overfeed highly degradable protein during hot weather it should be 18% or less.
Supplemental fat can be added in ration to increase energy in take. Also avoid feeding excess fat, over feeding causes problem with rumen function supplementing extra vitamins during summer has no added advantage.
Animal cooling system
Rise in ambient temperature activates sweat glands to produce sweat. Each gram of sweat evaporated from skin utilises 590 calories from skin surface (Latent heat of evaporation of water). This process of evaporation causes cooling of skin. A part form sweating animals increase their respiration rate.(induced evaporation of moisture from mouth/ lungs).
Breathing of animals at a much faster rate to combat heat stress leads to panting. To reduce the metabolic heat load, animals reject feed and fodder.
Use of water as cooling agent either directly on animal body or for cooling the shelter micro environment is as 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 and consequently reduces the heat load on animals. Grass screens on sides of shelter when with water considerably cool down the air passing through them. It requires proper cross ventilation.
