A Climatological Perspective on Feedlot Cattle Performance and Mortality Related to the Temperature-Humidity Index

This paper explores the climatology of high temperature-humidity index (THI) values (THI ≥ 84) in the U.S. Central Plains. The THI is derived from the dry bulb and the dewpoint temperatures. High THI values are associated with increased stress among feedlot cattle, which leads to a decrease in the rate of weight gain. When high THI values are sustained for several days, the result can be an increase in feedlot cattle mortality. We found that high THI values have a general southeast to northwest gradient across the region. We also introduce the concept of a THI-hour as a measure of the magnitude of a heat stress event. The THI values for a major heat-wave in 1995 are presented as well as a climatology of recovery hours (THI ≤ 74) during a heat-wave. The length of the recovery time during a heat-wave can mean the difference between life and death for feedlot cattle.