Modeling differences in feed intake and efficiency: Growing and finishing beef cattle

Objective

Our objective was to evaluate model structure choice on estimates of efficiency, based on residual feed intake, and thereby cattle profitability.

Materials and Methods

Efficiencies were compared for 2 models using data from 7 studies (509 cattle). Model 1 DMI were estimated using ordinary least squares as f(ADG and BW^0.750). Model 2 was a multivariable Bayesian model; DMI was f(ADG, BW^0.750 and BW). For model 2, DMI, BW, and ADG were ranked by model 1 residuals categorized in quintile to evaluate whether information found in residuals related to composition of gain or maintenance.

Results and Discussion

Efficiency rankings lacked concordance and predictive value between models, suggesting that ordinary least squares, Bayesian, or both frameworks lack utility to predict efficiency. With the exception of 1 data set, DMI was better predicted in the Bayesian framework. Estimated recovered energy (Mcal/d) in model 2 was less for cattle in quintile 1 than in quintile 5 for 4 of 7 data sets and numerically less for 6 of 7 data sets. Estimated maintenance in model 2 was less (quintiles 1 vs. 5) for 5 of 7 data sets. Substantial information existed in model 1 residuals regarding differences in composition of gain and maintenance not found in model 2 residuals.

Implications and Applications

Differing efficiencies between models indicate that residuals are properties of models, not cattle. Selection of cattle with less empty body fat may not be desirable from an economic standpoint.