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Title: Comparison of heat tolerance of feedlot heifers of different breeds

item Brown-Brandl, Tami
item Nienaber, John
item Eigenberg, Roger
item MADER, T
item Morrow, Julie
item Dailey, Jeffery

Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2006
Publication Date: 10/16/2006
Citation: Brown Brandl, T.M., Nienaber, J.A., Eigenberg, R.A., Mader, T.L., Morrow, J.L., Dailey, J.W. 2006. Comparison of heat tolerance of feedlot heifers of different breeds. Livestock Science 105:19-26. doi:10.1016/j.livsci.2006.04.012

Interpretive Summary: Heat stress in cattle causes the loss of millions of dollars each year due to reduced growth and death. A study was designed to look at stress among four breeds of cattle. The cattle ranged in color from black to white, and were observed throughout the summer. Breathing rates, behavior, and hair surface temperatures were recorded. In a second study, behavioral observations were made each hour on two cool days and two hot days. In the hot weather, all cattle greatly increased the time they spent drinking water, stood more, and ate less than on cool days. Overall, it was found the dark-hided cattle, especially those with more body fat, were more stressed than light-hided cattle.

Technical Abstract: Heat stress in cattle causes millions of dollars of losses each year due to production losses, and death losses in extreme cases. A study was designed to determine severity of heat stress among four genotypes of cattle. One-hundred twenty-eight feedlot heifers of four different genotypes were observed throughout a typical summer. Respiration rates, panting scores, and surface temperatures were taken twice a day on 10 animals/genotype for several weeks during the summer. Twenty-four hour behavior measurements were recorded for two heat-stress and two thermoneutral days. Results indicate dark-hided cattle were more stressed than light-hided cattle. Heat stress more than doubled drinking behavior, increased standing, and decreased eating, lying, and agonistic behaviors. Overall, it was found that dark-hided cattle with higher condition scores were more affected by heat stress.