Productivity of Holstein dairy cows without shade at two seasons of the year

In order to evaluate the effect of season on the productivity of Holstein dairy cows in a commercial herd, 10 cows were assigned to one of two treatments, cows in winter and cows in summer. The study lasted 70 days (d) divided into two periods of five weeks, respectively. The data were collected three times per week. The animals were under the same diet in both seasons, from an integral ration based on concentrate, alfalfa hay, and corn silo. The maximum temperature-humidity index was 70 and 75 units during the winter and summer, respectively. The cows in winter had lower (P<0.05) milk production, respiratory rate and rectal temperature than summer cows. The temperatures on the right flank and buttock area in winter cows were lower (P<0.05), with respect to summer cows. Drinking water, floor, and environment temperatures through the black bulb were consistently lower (P<0.05) during the winter season with respect to summer. Summer cows showed mild heat stress and increased 24% plus milk yield than winter cows, but did not improve milk quality. The use of shades during the summer can improve the physiological status milk quality in lactating dairy cows.