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 greater than or equal to 84) in the U.S. Central Plains. The THI is derived from the dry bulls and the dewpoint temperatures. High THI v alues are associated with increased stress among feedlot cattle, which lead s to a decrease in the rate of weight gain. When high THI values are sustai ned for several days, the result can he an increase in feedlot cattle morta lity. We found that high THI values have a general southeast to northwest g radient 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 is climatology of recovery hear s (THI less than or equal to 74) during a heat-wave. The length of the reco very time during a beat-wave can mean the difference between life and death for feedlot cattle.