Abstract #W50

# W50
Use of body measurements to estimate live weight of Holstein dairy calves in the pre-weaning period.
M. Hasnaoui*1, D. Santschi2, S. Plante1, E. Vasseur3, A. Bregard1, S. Binggeli1, É. Charbonneau1, 1Université Laval, Québec, QC, Canada, 2Valacta, Ste-Anne-de-Bellevue, QC, Canada, 3McGill University, Ste-Anne-de-Bellevue, QC, Canada.

The evaluation of body weight (BW) is one of the most effective ways to assess proper growth of calves and ultimately management. Although a scale is the best way to achieve this measure, most small dairy herds still rely on heart girth (HG) measurements with a tape to estimate calves BW. The equations linking HG measurements with BW were developed using animals of several weights, but rarely pre-weaning calves. The aim of this study was to validate the use of HG measurement for dairy calves in the pre-weaning period to estimate their BW and verify if other body measurements would also be effective to predict pre-weaning BW of calves. A database was built by weighting on a scale and measuring different parameter related to body size (HG circumference, withers height, hip height, and at the hip width) of 329 Holstein dairy heifers of 2 dairy farms in Quebec, Canada. The measures were taken 3 times per week during the first 3 weeks of life and every 2 weeks until the week following weaning at 76 d of age. Preliminary analyses with Pearson correlations were performed to assess the relationship between body weight and independent variables. Simple regressions were then performed using the MIXED procedure of SAS to predict body weight with calf as a random effect. Five-Fold cross-validation was used for each independent variable to evaluate the equations. The prediction equation for BW resulting in the highest r (0.99) and the lowest RMSPE (6.87) was using HG. The prediction equation with HG was BW (kg) = 119.04 − 3.3089 × HG (cm) + 0.02959 × HG2. Further analyses showed no mean bias (0.11 kg; P = 0.51) or linear bias (−0.002 kg, P = 0.47) for the proposed equation. In contrast, the most commonly used equation (Heinrichs et al., 1992; J. Dairy Sci. 75:3576–3581) exhibited a mean bias of 0.63 kg (P < 0.001) and a linear bias of −0.045 (P < 0.001). Predictions were also possible with the other parameters measured (hip width: r = 0.97, RMSPE = 9.92; withers height: r = 0.97, RMSPE = 10.82; hip height: r = 0.96, RMSPE = 11.38). The results of this study confirm the possibility to use HG or other body parameters to predict pre-weaning BW of calves.

Key Words: body weight, dairy calf, heart girth