Natural tree shade increases milk stability of lactating dairy cows during the summer in the subtropics.

This research communication addresses the hypothesis that, during the summer in the subtropics, natural tree shade helps to improve milk functional characteristics such as stability and acidity. Sixteen Holstein lactating cows were enrolled. The study consisted of three periods (pre-stress, heat stress and post-stress) based on allocating grazing cows into two treatments (with and without access to shade during the Heat Stress period). Overall THI during the trial was (mean ± se) 76.0 ± 3.4. Access to shade prevented the heat stress-related decrease in milk stability both in the ethanol and in the coagulation time test, as well as maintained milk acidity within an acceptable range (14 to 18°D).