Evaluation of body weight prediction equations and development of morphological models for day-old beef-on-dairy calves

The objectives of this study were to evaluate the accuracy of published equations for estimating BW of beef × dairy (B × D) male calves and to develop, test, evaluate, cross-evaluate, and validate new predictive equations based on morphological measurements of day-old B × D male calves. Three hundred twenty B × D male calves were enrolled upon arrival at the calf-raising facility, and morphological measurements such as BW, heart girth (HG), hip height (HH), and hoof circumference (HC) were recorded from each calf within the first 24 h of life. Forty-six published peer-reviewed equations were evaluated against the development dataset using root mean squared error (RMSE), concordance correlation coefficient (CCC), and mean squared error decomposition (mean bias, slope bias, and residual error) to assess agreement between observed and predicted BW. Moreover, 3 linear equations were developed using a forward selection criterion for HG (Equation 1), HG and HH (Equation 2), and HG, HH, and HC (Equation 3). In addition to linear models, evaluation of quadratic, cubic, and exponential models was assessed to determine the relationship between BW and morphological traits. Among the tested models, the linear equation proved more effective and simpler than the quadratic, cubic, and exponential models and was ultimately selected for validation. Overall, 76% of the published equations demonstrated poor agreement with observed BW, as indicated by an average CCC (0.49) and an average BW RMSE of 107.00 kg. An additional 17% of the published equations achieved moderate agreement, with average CCC values between 0.50 and 0.60 and an RMSE for BW of 6.20 kg; only 7% (the top-performing published equations) had CCC values greater than 0.60 and an RMSE for BW of 4.50 kg. All 3 developed equations exhibit greater predictive performance than 43 (93%) of the published equations, with an average CCC of 0.75 and an RMSE for BW of 3.50 kg. Cross-evaluation of the 3 developed equations demonstrated moderate to high BW-predicting performance (RMSE = 3.80 kg; CCC = 0.74). The validation assessment using an independent dataset of 176-d-old B × D male calves that only included HG as a morphological measurement indicated that the HG equation (Equation 1) had a moderate to high performance (RMSE = 3.80 kg; CCC = 0.64) in predicting the BW of day-old B × D male calves. Thus, indicating that this developed equation (Equation 1) can be applied as an on-farm tool to predict the BW of day-old B × D male calves.