Heat stress can cause reduction in milk production of 10-25 percent. The production and health benefits of cooling cows by a combination of fans and sprinklers have been well documented.
Sprinkling involves wetting the skin of the cows using large water droplet size to decrease water drift and to soak cows to the skin.
Cooling is achieved by evaporation of the water from the hair and skin due to moving air using fans. Fans should be run continuously, and sprinklers should be set to run 1 to 2 minutes on a 6 to 12 minute cycle dependent on temperature.
When planning to install a sprinkler system, it is important to take a systems approach. Before installing a system, the water supply should be checked to ensure adequate supply. The amount of water required is dependent on temperature, thermostat settings and size of sprayer nozzles. There is a large variation between studies that have documented water use by sprinklers. A 1989 study out of Kentucky used 83 gallons of water per cow per day using sprinkling for 30 seconds every 5 minutes when temperatures exceeded 80 degrees F.
Bray reported early studies in Florida which used 120 gallons of water per cow per day with a setting of 30 seconds per 5 minutes when temperature exceeds 80 F. In 1991, Bray later reported that 50 gallons per cow per day can provide adequate cooling. In 2002, Meyer reported water use on a commercial dairy in Kansas averaged 17 gallons of water per cow per day with 3 minutes of sprinkling followed by 12 minutes off and a water flow rate of 16 gallons per minute. Current recommendations by Harner at the 2013 Western Dairy Management Conference is to plan 15 to 20 gallons of water per cow per day during to summer sprinkler use.
To avoid slipping and potential hoof problems, the area where the sprinklers will be used should be properly sloped to allow excess water to drain away and avoid pooling.
Excess water, which will be contaminated with manure, should be contained, stored and properly managed. Cooling cows with sprinklers is an excellent reuse of excess plate cooler water. If the sprinklers will need to rely on fresh water, assess whether your manure management system can handle an additional 15 to 20 gallons per cow per day of water. Montoya reported in 1992 that 23 percent of the water sprayed was evaporated.
For a 100 cow dairy in Michigan that does not have plate cooler water available, this would total 180,000 gallons of extra water pumped (100 cows x 20 gal/cow/day x 90 days). Likely, only about 139,000 gallons would make it to containment after evaporation.
The above referenced studies looked at systems where sprinkling was being used both in the freestall barn and holding pen. An approach that can achieve moderate cow cooling and use less water would be to start by installing sprinklers and fans in the holding pen. The holding pen is often the hottest environment on the farm.
Cows will quickly experience heat stress when producing large amounts of body heat and brought into a confined space two or three times per day. Michigan State University Extension does not recommend installing sprinklers in the holding pen without mechanical ventilation which can cause more severe heat stress than no cooling because of a rapid increase in humidity.
The amount of water used in holding pen cooling has not been well documented. Harner recommends that sprinkler systems be capable of providing 0.03 gallons of water per minute per square foot of area.
Thermostat settings in the holding pen are recommended to be at 1 minute on, 6 minutes off, which is shorter than in the freestall area. Harner cautions that many water distribution systems may not be able to handle the high flow rate demands of the sprinkler system in addition to normal parlor water use.
Using water and fans in combination to cool cows is an effective way to cool cows during summer months. This approach uses large amounts of water which must be planned for in well capacity and storage.
Using recycled plate cooler water to cool cows can be an effective way of reducing the water demands on the farm.