Modeling the Effects of Environmental Factors on Finished Cattle

Abstract

Global concern about world climatic change and animal well-being has triggered greater attention regarding the effects of climatic anomalies on livestock. The objectives of this dissertation were: 1) to assess the effect of radiation components and other environmental variables on tympanic temperature and daily water intake of cattle; 2) to model tympanic temperature and daily water intake based on environmental variables, and 3) to assess the effect of soil surface temperature on comfort indices of cattle during summertime. In order to accomplish these objectives, a series of experiments were conducted during the period 2003 to 2008 at the University of Nebraska. Environmental variables were collected from a weather station located in the feedlot, whereas radiation measurements were collected using precision spectral pyranometers and precision infrared radiometers, which were located in empty pens during different months, years, and locations. Tympanic temperature, daily water intake, panting scores, and respiration rate were also collected in each experiment. Tympanic temperatures were collected using data logger devices (Stowaway and/or iButtons), which were fitted into the ear canal of steers. Statistical analyses included correlation, autocorrelation, repeated measures, simple and multiple regressions, and ANOVA. Soil surface temperature, outgoing radiation (long and shortwave), and wind speed had a significant effect on tympanic temperature during the summer. Thermal and solar radiation had a positive impact on the tympanic temperature of finishing steers during the summer when radiation received by steers was significantly greater than during the winter when no relationship was found. In addition, soil surface temperature was a novel and promising variable to be used to predict the tympanic temperature and daily water intake in finishing cattle. It is expected that in the future, it will be essential to collect more detailed information on the microclimate in feedlot operations. This will allow the incorporation of environmental conditions as a decision tool for managing heat stress.