Shade Material Evaluation Using a Cattle Response Model and Meteorological Instrumentation

Authors: Eigenberg, Roger; Brown-Brandl, Tami; Nienaber, John

Submitted to: International Journal of Biometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2009
Publication Date: 12/3/2009
Citation: Eigenberg, R.A., Brown Brandl, T.M., Nienaber, J.A. 2009. Shade Material Evaluation Using a Cattle Response Model and Meteorological Instrumentation. International Journal of Biometeorology. 53:501-507.

Interpretive Summary: Summer heat events are stressful to cattle in open feedlots. One method to reduce heat stress is to provide shade for the cattle, so a variety of materials are being tested. The question is what shade material will be the most effective. A summer study was conducted to compare effectiveness of several shade materials. The shades provided 100%, 60%, or 30% effective shading. Each shade structure used instruments to measure radiant energy received under the shade. Solar data were also collected in a non-shaded treatment in addition to weather data. The weather data were used to predict cattle stress response. A heat stress index was used to evaluate the effectiveness of the shades. Analysis showed that the shade reduced the predicted stress for all shade materials. However, important differences existed between shade materials (compared to no-shade) for periods of stressful daylight hours.

Technical Abstract: Shade structures are often considered as one method of reducing stress in feedlot cattle. Selection of a suitable shade material can be difficult without data that quantify material effectiveness for stress reduction. A summer study was conducted during 2007 using instrumented shade structures in conjunction with meteorological measurements to estimate relative effectiveness of various shade materials. 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 effective coverings of 100%, 60% with a silver reflective coating, and 60% black material with no reflective coating. Additionally, one of the structures was fitted with a poly snow fence with an effective shade of about 30%. Each shade structure contained a solar radiation meter and a black globe thermometer 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. Data analyses was conducted using 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 and for ‘full sun’ days.