Thermal heat stress can result in significant milk losses during the summer months. Many dairy producers suffered losses in production of up to 20 pounds per cow in 2002. Losses of this magnitude are preventable if heat abatement principles are applied. Capital expenditures on heat abatement systems have a rapid return on investment. Thermal heat stress is measured as Temperature Humidity Index (THI). THI is influenced not only by temperature, but by humidity as well. As the temperature rises and relative humidity increases, THI increases. Cattle find stress when THI exceeds 72. Others have suggested that feed intake will decrease when temperatures exceed 75 degrees. Kansas State University has done extensive research on dairy heat abatement practices. Research at Kansas used four different treatments. Cow respiration rates were measure every 5 minutes under each condition. Cows were soaked every five, 10, or 15 minutes Control group cows were not soaked and did not have fans. Airflow was none or 700 cfm delivered over the feedline. Water flow was .35 gallon/headlock/minute. The data suggested different cooling strategies for different levels of heat stress. Under severe heat stress, the sprinkler should run every five minutes with fans cooling the cows. Under moderate stress, running sprinklers every 10 minutes is adequate. Fans provide added cooling. During periods of low heat stress, sprinklers may run less frequently (every 15 minutes). The research clearly indicates 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 fans alone. Investing in installing sprinklers over the feed alley is minimal. Recommendations must be followed to allow for proper water flow. Contact the Carver County Extension for details. If resources are not limited, install the sprinkler system according to recommendations and install fans over the feedline and freestalls according to recommendations. If resources are limited, install the sprinkler system and install fans over the stalls. Using tunnel ventilation in tie stall barns is advised. Tunnel ventilation draws air through the facility by drawing air from one end of the building and exhausting it on the other end. Typical systems should have a minimal air speed of 220 feet of air per minute (5 miles per hour). An alternative for determining fans needs is to figure 1000 cfm/cow. Sprinklers, fans, and tunnel ventilation must be implemented correctly. Incorrect installation will not give satisfactory results. Plans and instructions are available. Contact Vern Oraskovich at the Carver County Extension Office for detailed information.
