Effect of drinking-water temperature on heat balance and thermoregulatory responses in dairy heifers

Abstract

A study was made to determine the effect of heat dissipation from drinking water (8 kg at 10, 20, or 30¦C) on the heat balance and thermoregulatory responses of 4 dairy heifers housed at 24, 29, and 34¦C. No effect of drinking-water temperature on heat production or heart rate was found. Respiration rate, mean skin-surface temperature, and rectal temperature all decreased with decreasing drinking-water temperature. Rectal temperature reached a minimum 20 min after watering. The respiration rate, skin temperature, and rectal temperature returned to prior-to-watering values 120-180 min after watering. The cooling efficiency of drinking water was about 40%, and decreased at high environmental temperature, because the cooling potential was used initially in depressing heat loss responses. It is suggested that in order to eliminate excessive heat load, chilled drinking water could be effective during the night time when the environmental temperature is lowest.