Effects of evaporative cooling on reproductive performance and milk production of dairy cows in hot wet conditions

Fourteen animals of second and third lactationof Thai Friesian crossbred cows (87.5% Friesian × 12.5%Bos indicus) located at Sakol Nakhon Research andBreeding Centre, Department of Livestock Development,Ministry of Agriculture and Cooperatives, were dividedrandomly into two groups of seven each to evaluate theeffects of evaporative cooling on reproductive and physiologicaltraits under hot, humid conditions. Resultsindicated that installation of evaporating cooling in theopen shed gave a further improvement in ameliorating heatstress in dairy cows in hot-wet environments by utilisingthe low humidity conditions that naturally occur during theday. The cows housed in an evaporatively cooled environmenthad both a rectal temperature and respiration rate(39.09⁰C, 61.39 breaths/min, respectively) significantlylower than that of the non-cooled cows (41.21⁰C;86.87 breaths/min). The former group also had highermilk yield and more efficient reproductive performance(pregnancy rate and reduced days open) than the lattergroup. It is suggested that the non-evaporatively cooledcows did not gain benefit from the naturally lower heatstress during night time.