Shade Material Evaluation Using a Cattle Response Model

Abstract

Cattle produced in open feedlots are vulnerable to a variety of weather events; under certain conditions heat events can be especially detrimental. Shade structures are often considered as one method of reducing cattle stress. A variety of shading materials are available; selection of a suitable material is difficult without data that quantify effectiveness of the materials on stress reduction. A summer study was initiated using instrumented shade structures in conjunction with meteorological measurements to estimate relative effectiveness of various shade materials. The shade structures were 3.6 m by 6.0 m by 3.0 m high at the peak and 2.0 m high at the sides. Polyethylene shade cloth was used in three of the comparisons and consisted of 100%, 80%, and 50% effective shading. Additionally, one of the structures was fitted with a poly snow fence instead of shade cloth. Each shade structure contained a solar radiation meter to measure radiant energy received under the shade material. Additionally, meteorological data were collected as a non-shaded treatment and included temperature, humidity, wind speed, and solar radiation. Analyses of the collected data focused on a physiological model that predicts cattle respiration rate based on relative humidity, ambient temperature, solar radiation and wind speed. An associated heat stress index was used to determine the effectiveness of the shading options. Analyses of the data revealed that time spent in the highest stress category was reduced by all shade materials. Moreover, significant differences (p<0.05) existed between all shade materials (compared to no-shade) for hourly summaries during peak daylight hours.