Sprinkling frequency and air flow also influence the efficiency of the cooling system. To increase the efficiency, cows must be dry before the next soaking cycle. The capacity to reduce the body temperature of cows during lactation was compared for different soaking frequencies (cycles every 5, 10, and 15 min.; Brouk et al., 2003). Each cycle supplied similar amounts of water in every treatment (0.35 gallon/headlock) during the same amount of time (1 min.). Air flow from the fans was continuous and supplied 700 cubic feet per minute (CFM). The drop in body temperature increased soaking frequency. These results suggested that the most effective system to alleviate heat stress is continuous forced air and soaking frequencies every 5 min. (1 min. on; 4 min. off). Subsequently, to corroborate whether the airflow influenced the cooling efficacy, three different airflows were evaluated (500, 750, or 900 CFM) with soaking frequencies every 5 min. (Brouk et al., 2004b). The system with the lowest airflow was the least effective, and there were no differences between the other two. This experiment demonstrated that there are no advantages to increasing the airflow above 750 CFM with a 5 min. soaking frequency.
Some facilities have chosen to install high-pressure misting systems to reduce the quantity of water used in a sprinkling system which, contrary to the sprinklers, eject very small droplets. If these drops are incapable of completely soaking the coat and skin of the cow, they can create an air space in between the skin and the water film. This air space insulates and can impede heat elimination through the skin and worsen the heat load of the animal.
According to Brouk et al., 2004b, a water-spraying system over the feed bunk together with forced air can have similar efficiency to the sprinklers (with 5 min. cycles) only when it soaks the skin of the cow completely. To achieve this efficiency, the system must be working continuously with a minimum water flow of 3.4 gallons per hour. When cattle are soaked with high-pressure misting, there is a combined effect of cooling the surrounding air and the animal through the water evaporated from the skin. Misters with water flow of 1.7 gallons/h were able to decrease body temperature in cows but were not as efficient as those with 3.4 gallons/h or sprinklers with 5 min. cycles. In addition, continuous high-pressure misting systems (3.4 gallons/h) use 18% less water than sprinklers in 5 min. cycles (1 min. on; 4 min. off; 4.2 gallons/h). There is a need for more production studies to corroborate whether this reduction in water use compensates for the greater increase in RH, particularly in high RH environments. There have been reports of higher incidence of respiratory problems in farms that use these systems, particularly when ventilation is inadequate and RH is high.