干旱区生态环境知识资源中心

To evaluate effects of short periods of cooling on physiological and productive parameters during summer, 27 first parity cows were grouped into control, 1 h cooling (C); 2 h cooling (AM); and 4 h cooling (AM + PM). The cooling system consisted of misting and forced ventilation. Skin temperatures were lower (P < 0.05) in the AM + PM group during the morning but higher (P < 0.01) in the afternoon, compared to C and AM groups. The respiratory rate was lower (P < 0.01) in the AM + PM group than in C and AM groups. Rectal temperature, milk production, milk protein, and milk energy output were similar among the groups. Conversely, milk fat was higher (P < 0.05) in AM + PM cows. Because use of a 4 h cooling period enhanced some physiological parameters and milk fat in primiparous Holstein cows, we recommend increasing the cooling period in arid regions to achieve higher performance and comfort of dairy cows.