Cooling Cows:

How Does Sprinkling Frequency and Airflow Impact Animal Response?

M.J. Brouk, J.F. Smith, and J.P. Harner

Kansas State University

Summer heat stress is just around the corner and the results of a study conducted by the dairy team from Kansas State University will help you keep your cows cooler this summer. Have you ever wondered if you should soak cows, increase airflow or both? Many producers have questioned which is most important. Last summer the team conducted a study to determine the effect of soaking frequency and airflow on respiration rates and skin temperature of heat stressed dairy cattle. Sixteen heat stressed lactating cows (8 primiparous and 8 multiparous) were arranged in a replicated 8×8 Latin Square design. Cattle were housed in freestall dairy barns and milked 2x. During testing, cattle were moved to a tie-stall barn for a 2-hour period from either 1- 3 pm or 3-5 pm on 8 different days in late August and early September. Afternoon temperatures ranged between 88 and 96 °F. During the testing period, respiration rates were determined every five minutes by visual evaluation. Skin temperature of three sites was measured with an infrared thermometer and recorded every 5 minutes. Treatments (Table 1) were 4 different soaking frequencies with and without supplemental airflow. Soaking frequencies were control (no soaking), every 5, every 10 or every 15 minutes. Supplemental airflow was either none or 700 cfm. Each soaking cycle provided similar amounts of water for all treatments. Initial data were collected for three 5-minute periods prior to the start of the treatments.

Cows soaked every 5 minutes with supplemental airflow (5+F) responded with the fastest and largest drop in respiration rate reducing the initial respiration rate by 47% at the end of 90 minutes of treatment (Figures 1 and 2). Soaking cows every 5 minutes without airflow (5) resulted in a similar response as soaking cows every 10 minutes with airflow (10+F). Soaking cows every 15 minutes with airflow (15+F) and soaking cows every 10 minutes without airflow (10) resulted in similar responses until the last 30 minutes of the study. Supplemental airflow without soaking (0+F) resulted in little improvement over no soaking or airflow (0). Soaking had a greater effect on respiration rate than airflow. However, the combination of wetting and airflow had the greatest effect on the respiration rate. When cooling heat stressed dairy cattle, the most effective treatment included continuous supplemental airflow and wetting every 5 minutes.

Skin temperatures are shown in figures 3, 4 and 5. Temperature of the thurl and ear were likely directly affected by the presence of water from the soaking procedure. However, the skin temperature of the rear udder was not directly affected by water from soaking. The rear udder skin remained dry throughout treatment. The reduction in rear udder skin temperature is the result of cattle directing less blood flow to the skin surface. This indicates that the cooling 2 systems were reducing heat stress as indicated by a reduction in respiration rates. The most effective treatment was the 5 minute soaking with supplemental air flow.

This data suggests that different cooling strategies could be developed for different levels of heat stress. Under severe heat stress soaking every 5 minutes with fan cooling will be the most effective. Under periods of moderate stress soaking every 10 minutes with fan cooling may be adequate. Reducing soaking frequency when temperatures are lower could significantly reduce water usage. Data clearly indicate that the combination of soaking and supplemental fan cooling are superior to either single treatment. If used singularly, soaking cows would have more impact than the use of fans only for cow cooling. These data indicate that about 1/3 of the total reduction in cow respiration rates was due to airflow and the remainder due to soaking. Under periods of severe heat stress, soaking every 15 minutes with airflow is not adequate and soaking frequency must be increased.

These data also suggest that different cooling strategies might be nearly as effective. For example, the effects of the 10 + F treatment were similar to those of the 5 minute soaking interval without supplemental airflow. This was also true of the 15 + F and 10 minute soaking interval without supplemental airflow. In situations where supplemental airflow is not provided, increasing soaking frequency may provide similar heat abatement as less frequent soaking with supplemental airflow. However, the data does clearly show that maximum cooling is achieved with frequent soaking with supplemental airflow.

Cow cooling with soaking and supplemental airflow is very effective in reducing respiration rate. Many systems may be ineffective because they do not deliver adequate water to soak the cow and/or have an inadequate soaking frequency.

Table 1. Experimental Treatments

*.35 gallon/headlock applied in 1 minute

Figure 1. Effect of Sprinkling Frequency and Airflow on Respiration Rate of Heat Stressed Dairy Cattle

Figure 2. Initial, Final and Percentage of Initial Respiration Rate of Heat Stressed Dairy Cattle Treated with Different Cooling Strategies

Figure 3. Cooling strategy effect on thurl skin temperature over 1.5 hours of cooling.

Figure 4. Cooling strategy effect on shoulder skin temperature over 1.5 hours of cooling.

Figure 5. Cooling strategy effect on rear udder skin temperature over 1.5 hour of cooling.