Shade Material Evaluation Based on Physiological Response of Cattle

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 32 heifers under 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 two of the comparisons and consisted of 100% and 60% effective shading; one of the structures was fitted with a poly snow fence instead of shade cloth. Additionally, a reference treatment with no-shade was included with one pen of heifers. Eight heifers were placed into each of the four treatment pens with average weights of 491 30.9 kg at the start and 520 35.0 kg at the end of the treatment period. Three heifers per treatment were equipped with automated respiration rate monitors. Each shade structure contained a solar radiation meter as well as a black globe thermometer under the shade material. Additionally, meteorological data were collected as a non-shaded treatment and included temperature, black globe temperature, humidity, wind speed, and solar radiation. The data analyzed in this study were collected from June 16th through August 18th, 2011. Preliminary analyses of the collected data focused on the effect of shade upon the heifers respiration rate. 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.