Using unmanned aerial vehicles to record behavioral and physiological indicators of heat stress in cattle on feedlot and pasture

Physiological and behavioral indicators of heat stress in cattle are time and labor-intensive to measure, and difficult to observe in extensive pasture settings. We proposed to record respiration rate and standing behavior using unmanned aerial vehicles. Videos were recorded above steers on feedlot in the morning (0830 – 1130) and afternoon (1400 – 1700) over ten days between July 25 – Aug 10, and cows on pasture over nine days between Aug 19 – 29. In the feedlot, video recordings on 925 individuals (264 black-coated, 413 red, and 248 white) were obtained, varying in breed which included Black Angus, Hereford, Charolais, Canadian Speckle Park, and Simmental. On pasture, video recordings on 267 individuals (116 Black Angus and 151 Hereford) were obtained. Observer software was used to analyze videos. Respiration rate in feedlot cattle was the highest in black cattle, followed by red cattle, then white cattle. Coat color did not affect respiration rate in cows on pasture; temperatures on pasture were lower than in feedlots and the effect of coat color may not manifest until a certain ambient or black globe temperature threshold. The probability that cattle would be standing increased with heat load index in feedlot and pasture settings.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author