Dairy--Animal Management

KEEPING DAIRY COWS COOL

General

During periods of hot weather, cows have a difficult time keeping cool. As the air temperature rises to a point close to their body temperature, cows are unable to lose body heat to the environment as efficiently. Animals will generally pant to reduce body heat when overheated. If body heat can not be lost their body temperature will rise eventually causing death.

There are several steps that will help cows to keep cool during hot weather. These include shade, air flow, and sprinkling water.

Shade

The most simple prevention measure is providing shade. Animals that are forced to stand in sun gain heat from the sun and will have more difficulty dissipating to their surroundings. Barns that are used for shade should have high, open sides to allow air to flow through them. An open roof ridge allows hot air to escape from the building and keeps it cooler. Additionally, barns with insulation under the roof help to keep cows cool. In uninsulated barns heat is radiated to the animals from the very hot underside of the roofing.

Air Movement

High roofs, as discussed above, allow for natural ventilation of structures. However, on a hot, calm day natural ventilation is minimal. Fans may be used to circulate air across the animals to reduce heat stress. Cows, like humans, will lose moisture through the skin. About 1000 btus per pound of water evaporated is removed from the animals body and therefore keeps it cooler. Fans should be placed 30 feet apart if 36 inch fans are used and 40 feet apart if 48 inch fans are used. Angle fans slightly down to blow air directly on the cows. Cover fans with wire mesh to reduce the chance of injury to animals or workers.

Sprinkler System

The final measure that may be taken is artifically wetting the cows. This is done using a sprinkler system in the feeding or holding areas. The sprinkler system intermittenly wets the cows using large droplets of water. Fans blow air continuously over the animals to evaporate the water and cool the cows. The objective is to apply just enough water to get the cows throughly wet to the hide. The interval between sprinklings should be long enough so that the cow is almost (but not quite) dry before she is sprinkled again. There are differences in opinion on the temperature to start the system. Some researchers have suggested 78 degrees while others think you should wait until 85 degrees. Sprinklers should have the following characteristics:

  1. Solid-cone, course-droplet
  2. 360 degree
  3. 7 to 30 gallons per hour
  4. System pressure of 20 to 25 psi
  5. 45 degree or greater spray angle
  6. Mounted to wet the entire floor area
Sprinklers should be on 3 minutes out of 10 to start with. If cows are wetted too much, heat loss will be reduced rather than improved because water will act as an insulator. Never wet areas that are used for bedding areas such as free stall barns.

Possible Results

Tests have shown that, compared to no fan and sprinkler system, this system increases milk production between 7 and 16 percent, increases feed consumption 7 to 9 percent and reduces panting 18 to 40 percent.

For further information on system design, contact a county Extension office.