PSIV-2 Evaluation of Relationship Between Feed Efficiency Traits and Energy Metabolism Using Comparative Slaughter Studies in Growing and Finishing Cattle

Abstract

Abstract There is uncertainty whether feed efficiency traits are related to energetic efficiency. The objective of this study was to utilize comparative slaughter data to evaluate the relationships of feed efficiency traits with maintenance energy requirements (MEm) and efficiency of metabolizable energy (ME) use for maintenance (km) and gain (kg). Published data were compiled (31 studies, 214 treatment means) on metabolizable energy intake (MEI) and composition of empty body gain in growing cattle. Data analyses were performed using R statistical software considering each treatment mean as an independent experimental unit. Assuming fasting heat production (FHP) varies only due to empty body protein (EBP) composition, it was computed as 295 kcal/kg EBP.75. MEm, km, and kg were computed from the nonlinear relationship between heat production and MEI. Residual intake (lower is more efficient) was computed as the residual from linear regression of MEI on EBW and EBW gain (RMEI) or MEI on EBP, retained energy as protein and retained energy as fat (RMEIc). Residual gain (higher is more efficient) was computed as the residual from linear regression of EBW gain on EBW and MEI (REBG) or retained energy on EBP and MEI (RRE). MEI was positively correlated with RMEI (0.46) and RMEIc (0.44), and EBW gain was correlated with REBG (0.58) and RRE (0.39). FHP was correlated with RMEIc (-0.25). MEm was weakly correlated with RMEI (0.19), RMEIc (0.22), and REBG (-0.26), but strongly correlated with RRE (-0.51). km was moderately correlated with RMEI (-0.35), but strongly correlated with REBG (0.49), RMEIc (-0.59), and RRE (0.79). kg was strongly correlated with RMEI (-0.69), REBG (0.47), RMEIc (-0.89), and RRE (0.70). Correlations among feed efficiency traits were strong (>±0.48). In conclusion, feed efficiency traits using retained energy as the dependent variable had stronger correlations with maintenance energy requirements than those using feed intake as the dependent variable.