Comparison of visual assessment and heart girth tape measurement for estimating the weight of cattle in clinical practice.

Estimates of the weights of dairy cattle by veterinary surgeons (n = 53), stock handlers (n = 42) and students (n = 77) were compared with heart girth measurements, which were used as a predictor of bodyweight. Visual live weight estimation was variable in accuracy. Fifty-five per cent of weight estimates were >10% from the reference weight, and the mean absolute percentage difference for all estimates was 15% (standard deviation 15%, interquartile range 5-20%). Underestimation was more frequent at higher weights, and accuracy of estimation was lower as weight increased. Overestimation tended to occur more frequently at weights <150 kg.