Submitted to: International Journal of Biometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2013
Publication Date: 8/23/2014
Citation: Howard, J.T., Kachman, S.D., Snelling, W.M., Pollak, E.J., Ciobanu, D.C., Kuehn, L.A., Spangler, M.L. 2014. Beef cattle body temperature during climatic stress: a genome-wide association study. International Journal of Biometeorology. 58(7):1665-1672. Interpretive Summary: The ability of cattle to adapt to heat and cold stress can be economically important in extreme climates. At least a portion of this adaptive potential is under genetic control. This study identified genomic regions that explain variation in cattle’s ability to regulate body temperature during extreme heat and cold events. For the population examined, larger portions (20 – 68 %) of the variation in body temperature during stress events was explained using DNA markers. The genomic regions identified may indicate physiological mechanisms involved in thermoregulation.
Technical Abstract: Cattle are sold for use in multiple environments that differ greatly in multiple climactic parameters, making the ability to regulate body temperature across multiple environments essential. Collecting phenotypic body temperature measurements is difficult and expensive, thus a genomics approach is highly applicable. To locate genomic regions responsible for body temperature regulation, we evaluated crossbred steers and heifers (n=239) with varying percentages of Angus, Simmental, and Piedmontese. Cattle were placed in a feedlot in four groups across two years. During predicted heat and cold stress events, hourly tympanic and vaginal body temperature devices were placed in steers and heifers, respectively. A Genome-wide association study was conducted for area under the curve (AUC), a measure of body temperature over time, using hourly body temperature observations summed across five days (AUC summer 5-d (AUCS5D) and AUC winter 5-d (AUCW5D)) and during the maximal 24-h stress cycle (AUC summer 1-d (AUCS1D) and AUC winter 1-d (AUCW1D)) using an approximation of the trapezoid rule. Animals were genotyped with a panel of 50,000 genetic markers and data analyzed using Bayesian models. Posterior heritability estimates were moderate to high and were estimated to be 0.68, 0.55, 0.21, and 0.20 for AUCS5D, AUCS1D, AUCW5D, and AUCW1D respectively. Moderately positive correlations between Genomic-EBV for AUCS5D and AUCW5D (0.40) and AUCS1D and AUCW1D (0.50) were found, although a small percentage of the top 5% 1-Mb windows were in common between winter and summer stress events. Selection for heat tolerance may result in an animal that is cold intolerant, or vice versa.