The Effects of Heat Stress on Production, Metabolism and Energetics of Lactating and Growing Cattle

Heat stress negatively impacts a variety of dairy and beef parameters including milk yield, growth and reproduction and therefore is a significant financial burden (~$900 million/year for dairy and > $300 million/year in beef in the U.S.; St. Pierre et al., 2003). Advances in management (i.e. cooling systems; Armstrong, 1994; VanBaale et al., 2005) and nutritional strategies (West, 2003) have alleviated some of the negative impact of thermal stress on cattle, but production continues to decrease during the summer. Accurately identifying heat-stressed cattle and understanding the biological mechanism(s) by which thermal stress reduces milk synthesis, growth and reproductive indices is critical for developing novel approaches (i.e. genetic, managerial and nutritional) to maintain production or minimize losses during stressful summer months.