John C. Lin, B.R. “Pete” Moss, Joe L. Koon, Cliff A. Flood, and Robert C. Smith, III

KEEPING COWS COOL during hot, humid weather is a critical concern for southern dairy producers because hot cows eat less and, thus, produce less milk. AAES research is showing that misting systems are economical and efficient approaches for keeping dairy cattle cool and comfortable.

Producers have several options for cooling cattle, including the use of fans, sprayers, misters, or combinations of these approaches. Systems that use water in the cooling process have proven effective; however using water in the dairy barn can be expensive and also contribute to problems with runoff from dairy facilities. AAES researchers have been evaluating various cooling systems to determine which ones are most efficient and effective for Alabama producers.

Studies were conducted at the E. V. Smith Research Center Dairy Unit in Shorter during the summers of 1994 and 1995 to evaluate the effects of different cooling treatments on lactating Holsteins. Cows (48 in the first year, 52 in the second year) were assigned to one of four treatment groups: (A) limited time in the barn with fans, (B) in the barn with fans only, (C) in the barn with fans plus direct spray, or (D) in the barn with fans plus water misters.

Cows in treatment A stayed outside from 6-9 a.m. and 5 p.m.-1 a.m. daily. Cows in the other treatments remained inside except for two hours of outside exercise daily. In each treatment, two Turbo-Aire fans were mounted every 25 feet and ran continuously when air temperature exceeded 78°F. Fans used for treatments A, B, and C were placed eight feet from the ground both years of the study. In 1994, fans for treatment D were placed 10 feet high, but lowered to seven feet in 1995 because, in the first year, mist was caught in updrafts and carried out of the barn through roof vents. Therefore, it did not reach the backs of cows.

The direct-spray system (treatment C) consisted of five 0.0625-inch diameter, solid-cone low-pressure nozzles (Senninger 1800, Model #9; 1.77 GPM at 10 psi) mounted on half-inch PVC pipe installed along the feed bunk at a height of six feet, two inches and spaced about seven feet, six inches apart. Sprayers were turned on automatically for three minutes of every 15 minutes whenever the temperature was above 82°F. For treatment D, each fan was equipped with circular tubing that contained four, hollow cone nozzles (0.016 in. diameter; 1.2 GPH at 60 psi). In addition, a 10-foot bar with four similar nozzles was placed in the front of each fan. Misters around the fans and on the bar were turned on automatically when the temperature exceeded 82°F and 85°F, respectively.

The outside temperature during the test periods (June, July, and August) of both years, especially during 1995, was very high with many day-time temperatures of 95° to 100°F and night time temperatures of 75°F. Temperatures and humidities of both years were determined for the four different treatments (see the table). Temperatures were not different between the direct spray and mister areas, but both were lower than the area where only fans were placed. As expected, the relative humidity was higher for areas with direct spray or misters than the areas with fans only.

Cows seemed to be more comfortable in the areas with direct spray or mist. To determine this, the respiration (breathing) rate was counted as flank movement of five cows per group each week. Cows in groups without any
water cooling had to breathe more often to keep cool than did cows in the spray or mist systems.

Individual feed intake was determined through group feed consumption divided by number of cows in the group. In both years, cows under the direct spray and misters consumed more feed than those with only dry fans. However, there were no differences in milk production between cows under misters and those under dry fans in 1994. In 1995, the feed dry matter intake was about five pounds more per day (13% higher) for cows in the direct spray fan and mist-fan treatment areas than for cows in the other two treatments. Milk yield was about seven pounds more per day (15.3% greater) for cows with water systems compared to cows without the water cooling treatments.

There were no differences in daily milk production between cows in the direct spray-fan (52.8 pounds) and the mist-fan (53.2 pounds) treatments, when the misters were lowered. Milk fat percentage was lower for treatment A cows allowed outside for extended time each day in 1994, but did not differ among the treatments in 1995. Milk protein was lower for those treatment A cows allowed outside for longer periods in 1995. Body
weight gains did not differ among the treatments in 1994, although there were some slight differences in 1995. The mister system used much less water than the direct spray system in both years.

These results indicate that cooling cows with water applied through either a mist or spray can increase milk production if the system is installed properly. Overall, the combination of mister and fan cooling system provided the best choice of this study, because water use and waste-waterrunoff were reduced compared to the spray system.

Lin is a Research Associate and Moss is a Professor of Animal and Dairy Sciences. Koon and Flood are Associate Professors of Agricultural Engineering. Smith is Superintendent of the E.V. Smith Research Center Dairy Unit.