Alternative Cooling of Dairy Cows by Udder Wetting
Heat stress is a major inhibitor of production in livestock operations, causing severe economic loss. The objective of this study was to explore an alternative way to cool cows in time of heat stress by wetting the udder, as opposed to the common practice of wetting the body. Twelve pregnant, lactating Holstein cows were used in the study. The cows were exposed to four treatments each day over four days. The treatments were: (1) wetting the body without blowing air (n = 24), (2) wetting the body and blowing air (n = 12), (3) wetting only the udder without blowing air (n = 24), and (4) wetting the udder and blowing air directly onto the udder (n = 12). Water was sprayed over both sides of a cow’s back until it dripped. Similarly, this was done for the udder wetting treatment. Fans were used to blow air onto the wet area and were turned on until measurements of rectal temperature, respiration rate, and skin surface temperature, both at the udder and body (dorsal), were taken. Respiration rates and skin temperatures were higher (p > 0.05) with udder wetting compared to body wetting. However, there was no statistical difference in rectal temperature between both wetting cases with or without blowing air onto the wet surface. Since rectal temperature is a measure of internal body temperature, it can be concluded that udder wetting alone was as effective as body wetting in abating thermal stress of dairy cows. Blowing air onto the wet udder further lowered udder skin surface temperature. There was a strong correlation (R = 0.91) between vaginal and rectal temperatures. Vaginal temperature, which provides the ability to continuously record over a prolonged time by implanting a sensor in the vagina, could be considered as an accurate and reliable measure of body temperature of healthy dairy cows.