Effects of Coat Color on Body Temperature and Grazing Time of Beef Cattle Grazing Fescue Pastures in Southwest Missouri

This study was designed to study the effects of coat color on body temperature and grazing time of 46 Hereford and Black Angus/Limousin beef cattle grazing fescue pastures in Southwest Missouri. Experiment one included an undisturbed setting and the second included a controlled setting. All cattle were categorized by treatment (color). Variables recorded during experiment one included sex, color, rectal temperature, skin temperature, rib fat, hair score, Thermochron iButton™ temperature, ambient temperature and wind speed. Variables recorded during experiment two included sex, color, ambient temperature, humidity and wind speed. In experiment one iButtons™ were attached to CIDRs® a device normally used to synchronize estrus by administration of exogenous progesterone. These devices were then inserted vaginally into heifers in order to record internal body temperatures at 10-minute intervals. Statistical analysis was done using Minitab GLM procedure. Throughout experiment one, ambient temperature showed an effect on iButton™ temperature (P<0.001). Internal temperature measured by iButtons™ were affected by either rib fat (P<0.0001) or hair score (P<0.0001). For experiment two, black heifers spent more time in the shade than dark red heifers. Assessing behavior due to heat stress among cattle in combined groups resulted in similar patterns of behavior regardless of ambient temperature. However, when cattle were separated under a controlled setting, behavioral differences were observed between coat color groups.