Effects of one-hour daily outdoor access on milk yield and composition and behaviors of tethered dairy cows.

Abstract

We investigated the effects of outdoor access for one-hour per day (ODA) on milk yield and composition and behaviors of tethered dairy cows. Eleven all-day tethered dairy cows were treated with ODA for two weeks. To evaluate the effect of ODA on milk yield, we first calculated the average daily milk yield of each cow for three days during two weeks before the ODA, three days before the ODA, three days at the end of the ODA, and three days during two weeks after the ODA. We then compared the milk yield change during the ODA with that for two weeks before and two weeks after the ODA. The effects of ODA on milk compositions and behaviors were evaluated by comparing the average values for each composition and behavior for the three days before the ODA and the last three days of the ODA. The decrease of milk yield during the two weeks of ODA was significantly higher than that during the two weeks before ODA (p<0.01). The milk fat rate was significantly higher during ODA than before ODA (p<0.05). Lactose rate was significantly lower during ODA than before ODA (p<0.05). The concentrations of milk urea nitrogen, ketone bodies, and free fatty acids in the milk were significantly higher during ODA than before ODA (p<0.05). The mean total duration per day of lying during ODA was significantly lower than that before ODA (p<0.05). The walking steps per one-hour outdoor access were 158.4±54.7. The social behavior during the one-hour outdoor access of the 11 cows was 53 times/h/herd. Our results suggested that ODA promotes the expression of normal behavior in dairy cows, but even one hour of ODA decreases milk production in cows, which may drop producers' profits without some financial supplementation.