Accuracy of prediction of the liveweight of horses from body measurements.

Fifty-three horses, all but two of them over two years of age and varying in type, sex and liveweight (230 to 707 kg) were weighed and seven different body measurements were recorded in duplicate by a single operator. The best overall prediction of liveweight using an equation with two variables was found to be: liveweight (kg) = (umbilical girth [cm])1.78 X (length of body from tuber ischii to elbow [cm]0.97/3011). This equation had an adjusted R2 value of 94.9 per cent and was derived from the pooled data, because differences of sex, type and weight did not significantly affect the relationship. The stable behaviour of the relationship was demonstrated by the fact that about 95 per cent of the residuals lay within +/- 53 kg, giving an average error of 4.7 per cent. The accuracy of prediction of the equation was better than the accuracy of four other established equations. A nomogram based on the equation is given.