Effect of Improved Cooling System on Reproduction and Lactation in Dairy Cows under Tropical Conditions

The effects of utilizing evaporative cooling system equipped with tunnel ventilation on postpartum ovarian activities, energy balance and milk production of early lactating dairy cows under hot and humid climates were studied from parturition to 22 wk postpartum. Thirty-four crossbred Holstein-Friesian (93.75% HF×6.25% Bos indicus) primiparous cows were randomly assigned to one of two groups. Cooled cows (n = 17; treatment) were housed in the tunnel ventilated barn equipped with evaporative cooling system and uncooled (n = 17; control) were housed in the naturally ventilated barn without supplemental cooling system. Cooled cows had greater (p<0.05) dry matter intake and milk production than uncooled cows. Days to the energy balance (EB) nadir did not differ between groups. However, days to equilibrium EB for uncooled cows was longer (p<0.05) than for cooled cows. There was no significant difference in postpartum anovular condition between cooled and uncooled cows. The interval from parturition to first postpartum ovulation did not differ between groups (31.4±4.3 and 26.1±3.6 day, respectively). These results suggest that the evaporative cooling and tunnel ventilation has the potential to decrease the severity of heat stress and improve both milk production and metabolic efficiency during early lactation without affecting reproductive function in dairy cows under hot and humid climates. (