Effectiveness of low pressure misters for cooling lactating dairy cows

Summary

Low pressure misters used with conventional fans provide effective supplemental cooling for lactating dairy cows during heat stress and use 43% less water compared with high pressure misters.

Situation

Heat stress occurs when the temperature humidity index exceeds 72. In much of the Southeast, chronic heat stress conditions persist for much of the summer and early fall. During heat stress, intake decreases in response to high body temperatures resulting in decreased milk yield for lactating dairy cows or lower body weight gain for growing replacement heifers. To reduce the degree of heat stress, supplemental evaporative cooling is provided through a combination of sprinklers or misters and fans. These systems have been shown to reduce the animals body temperature and maintain intake and performance, but the systems use a large volume of water. Recently a low pressure mister system was introduced that potentially requires less water and can effectively cool cows, but no data are available on the performance of this system in a hot, humid climate.

Response

A total of forty Holstein cows were used in a replicated switch-back trial during the summer of 2009 to evaluate the effectiveness of a low pressure mister system to cool lactating dairy cows and reduce water usage compared with a high pressure mister system. Each system was mounted on the front of 36 inch high speed fans located over the feed alley and free stalls. Both systems were controlled by a thermostat which automatically turn on the fans when the temperature exceeded 72 F and a humidistat that turned on each mister system when the humidity was less than 85% and the fans were operating. Core body temperature of each cow was recorded every 5 minutes for three consecutive days each week using a water temperature probe placed in the vagina of each cow. Water usage was recorded using inline water meters for each system. Environmental conditions in the free stall barn were recorded continuously throughout the trial.

Impact

The temperatures and humidity during June and July were consistent with chronic heat stress conditions typically observed in the Southeast resulting in a temperature humidity index greater than 72 throughout the trial. The core body temperature of the cows was similar for both systems and averaged 101.83 and 101.82 for low and high pressure mister systems, respectively. No differences were observed in respiration rates which averaged 61.5 breaths/minute. Water usage was 43% lower with the low pressure system compared with the high pressure system. These results suggest that a low pressure mister system can be used to effectively cool cows and reduces the volume of water required for supplemental cooling.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2009
• Geographic Scope: International
• County: Tift
• Program Areas:
  • Agriculture & Natural Resources