Physiology and management: Effects of Bovine Somatotropin and Evaporative Cooling Plus Shade On Lactation Performance of Cows During Summer Heat Stress

摘要

Thirty-two Holstein cows (8 per treatment) averaging 195 d in milk were assigned to d of treatment on the basis of production during a 14-d pretreatment period, which was used for covariate analysis. The experiment was a randomized block design with a 2 × 2 factorial arrangement of treatments. Factors were normal shade or shade plus evaporative cooling with pressurized spray, plus with or without the administration of bovine somatotropin (bST). Cows receiving bST were injected with 500 mg of bST every 14 d.