EVALUATING 2 DIFFERENT EVAPORATIVE COOLING MANAGEMENT-SYSTEMS FOR DAIRY-COWS IN A HOT, DRY CLIMATE

Milk production, rectal temperature, live weight gain, reproductive pe rformance, and weather data were obtained on 150 Holstein cows managed under two cooling systems on a large dairy farm in Saudi Arabia durin g the summer months. Cows were paired at the onset of the trial accord ing to days postpartum, lactation number, and current milk production. Females were then allocated either to a system that forced air, preco oled by evaporative cooling, over the cows or to a system that alterna tely showered a fine mist onto the surface of the cows and then forced air at ambient temperature over them. The cows receiving evaporative cooling and those with spray and fan cooling were on sand and on slatt ed concrete floor, respectively, during the periods of cooling. The on set of estrus was observed during the night when the cows preferred th e unshaded corral. For the 120-d trial period, 84% (62 of 75) of the c ows receiving evaporative cooling and 60% (44 of 75) of the cows recei ving spray and fan cooling became pregnant. In the evaporative cooling system, the pregnancy rate per insemination was 35.2% (179 inseminati ons) versus 23.2% (194 inseminations) for spray and fan cooling. The m ean postpartum interval to pregnancy was 117.6 d for the evaporative c ooling cows and 146.7 d for spray and fan cooling cows. The evaporativ e cooling system, with its open shades and sand bedding, enhanced repr oductive performance and milk production compared with that of cows co oled with a spray and fan system with slatted flooring in this hot cli mate.