The effect of diet type on residual feed intake and the use of infrared thermography as a method to predict efficiency in beef bulls
Residual feed intake (RFI) is a recognized measure of biological efficiency in beef cattle. However, RFI determination is expensive, time consuming and not well studied in animals fed forage-based diets. The objectives of this experiment were to investigate infrared thermography (IRT) as method for determining RFI ranking in yearling beef bulls, and to evaluate the effect of diet type on RFI repeatability in consecutive feeding periods. No significant correlations (P > 0.05) were observed between eye or cheek surface temperatures measured using handheld or within-pen stationary infrared camera systems with RFI. Reranking was observed for RFI in all diet treatments, however significant repeatability estimates occurred for the forage and grain diet treatments (r=0.58 and 0.64 respectively; P < 0.01) but not the diet switch treatment (r=0.24; P > 0.05). Extreme cold temperatures experienced in Western Canada influence IRT measurements and energy partitioning, indicating the need for standardized performance testing procedures.