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Chill Out With Supplemental Cooling

Summer's no bummer if you keep your cows cool

KEVIN JANNI
Department of Biosystems and Agricultural Engineering, University of Minnesota

Do you have trouble with decreased production and breeding problems in the summer? Maybe you should be thinking about installing supplemental cooling now. Many dairy producers find that supplemental cooling can help cows maintain milk production and breeding efficiency during hot weather.

You can provide supplemental cooling:

In holding pens
Alongside feed mangers or fences
In close-up (dry) cow pens
Over freestalls
In maternity and sick/treatment pens

Supplemental cooling cannot fix problems caused by inadequate or improper ventilation. Make sure that the area is properly ventilated and shaded before spending money on supplemental cooling.

Supplemental cooling can be provided using:

Cooling or mixing fans
Fans and sprinklers
Fans and misters

Sprinklers and misters are not interchangeable. Their design and mode of action are very different. Sprinklers soak cows to the skin, so their body heat is used to evaporate the water. Misters create a very fine mist, which evaporates in the air and cools the air. Improperly designed systems may not provide the needed cooling effect. They may also create wet conditions that lead to increased mastitis.

Cooling Fans

In all cases the first step is to add mixing fans to create a draft across or past the cows, which helps remove body heat. Direct-drive axial-flow fans are preferred, primarily because they retain their performance over time better than belt-driven fans. Most mixing fans are 36 or 48 inches in diameter and normally installed about 10 to 12 feet above the cow feeding alley, or high enough to clear equipment operating below the fans. Fans over freestalls are usually mounted 8 feet above the cow alley or higher if necessary to keep cows from reaching the fans. The fans are angled downward 15 to 20 degrees. The goal is to create air velocities around 200 to 300 feet per minute across the cows' backs. The recommended distance between fans is 30 feet for 3-foot diameter fans and 40 feet for 4-foot diameter fans. All fans should be blowing air in the same direction. Most cooling fans in naturally ventilated barns are mounted to blow air toward the east or north. Mixing fans are usually controlled with thermostats that turn the fans on at 70^o F and above.

In holding areas where clearance is limited, fans can be mounted along the side of the holding pen with the airflow directed across the animals. Again, all fans should blow air in the same direction. Don't blow air toward the milking parlor. Mount the fans securely and provide guards and screens to prevent cows from reaching moving parts and electrical wiring.

Fans and Sprinklers

Low-pressure sprinklers and fans can be used along feed bunks and in holding areas where there is good ventilation (air exchange) and it doesn't matter if the floor gets wet. The fans run continuously while the sprinklers turn on and off. The sprinklers are on long enough to wet the cows' hair and coat to the skin--typically 1 to 3 minutes every 10 to 15 minutes. Excess sprinkling wastes water and does not reduce heat stress. The cows feel cooler because some of their body heat is used to evaporate the water. It is critical that the sprinklers be turned off for evaporation to occur. Adequate air exchange is essential to remove the humidified air.

Install sprinklers so they will not wet feed in the feed bunk or bedding in the freestalls. (Wet bedding can lead to an increase in mastitis.) Use either 180-degree (half-circle) or 360-degree (full-circle), low pressure (20 to 25 psi) sprinkler nozzles that produce a shower of large droplets that readily wets the cows' skin, not a fine mist. Irrigation nozzles and solid-cone coarse droplet spray nozzles with flow rates between 0.2 and 0.5 gallons per minute work very well. Along a feed manger, 180-degree nozzles mounted next to the bunk so they spray away from the bunk minimize feed wetting. The 360-degree nozzles work well in holding areas.

Use sprinkler supplier information to determine nozzle spacing based on water pressure. Space nozzles so that the system provides a uniform distribution. Size water lines adequately to provide sufficient water flow and minimal pressure drop to produce a more uniform spray, especially along long feed bunks. Consider installing a pressure regulator to keep the water pressure within operating limits. Excessive pressure may produce a mist or smaller droplets that do not wet the cows' hair to the skin.

Sprinkler systems can be automatically controlled using a thermostat and 30-minute cycle timer in series. Sprinkler systems are usually set to turn on when air temperatures exceed 78^o to 80^o F.

Fans and Misters

High-pressure misters (sometimes called foggers) operate at pressures around 200 psi. They create very fine droplets that evaporate in the air, reducing the air temperature a few degrees. Fans then blow the cooler air past the cows. The amount of cooling achieved depends on air temperature, relative humidity, and the amount of water mist evaporated. Misting systems work best in dry climates. Adequate ventilation (air exchange) is required to remove the humidified and heated air.

Misting systems run continuously when cooling is needed. Some can be mounted directly on cooling fans. Booster pumps are required to provide the water pressure needed to create the fine droplets. A properly designed, installed, and maintained misting system can cool air without wetting cows or their surroundings, so they can be used where sprinklers cannot. Be sure to keep them working right, however. Improperly operating units can quickly wet a considerable area.

Misting systems suffer from nozzle plugging. Water filters reduce plugging, but add to the maintenance required. Use piping and connectors that can handle the water pressure required by the nozzles. Size pipes to provide adequate water flow and minimal pressure drop.

Misting systems can be automatically controlled using a thermostat. Misters are usually set to turn on when air temperatures exceed 78^o to 80^o F.