Determining best predictors of animal performance in feedlot steers
Metadata[+] Show full item record
Two studies were performed in a feedlot environment to determine the long-term effects of heat events on animal performance and well-being. Experiments in this thesis were designed to pinpoint ambient variables that most strongly elicit animal thermoregulatory responses. These animal responses included core temperature (Tcore) alone in the first study, and both Tcore and animal respiration rate (RR) in the second. Both experiments went a step further by using both ambient conditions and animal responses to predict feed intake (FI) response to heat stress. The ability to predict FI based on measurable independent variables could be very helpful to beef producers who are otherwise subject to environmental stressors and loss in animal production. The first study followed 26 crossbred Angus steers during 42 days of a central Missouri summer in 2011 (July 12 through August 22), and was strictly aimed at predicting Tcore and FI using ambient information. Animals were housed at the University of Missouri Beef Research and Teaching Farm (BRTF) in Columbia, Missouri and had ad libitum access to feed and water, with [about]50% shade coverage over the pens. All variables were automatically measured and recorded throughout the entire study period. Linear and polynomial regression analyses of variance (ANOVA, JMP statistical software; SAS Institute; Cary, NC) were used. Both ambient and mean herd Tcore readings were averaged by hour to analyze the relationship between environment and Tcore during daytime (0700 to 1700 CST).