Predicting body weight from body measurements of pre-pubertal Ayrshire heifers

The relationship between heart girth, wither height, body length and body weight in 3- to 9.5-month-old pre-pubertal Finnish Ayrshire heifers gaining 600-650 g/d was analysed (experiment I). Regression analysis showed that heart girth was the trait most highly correlated to body weight (R(2) = 0.969). Including body length or wither height as a second term in the regression, increased R(2) values only slightly. When the relationship between heart girth and body weight was used to predict the body weight of heifers reared at two feeding levels (experiment II), the precision of prediction was affected by the plane of nutrition. Actual body weight for a given heart girth was slightly higher on the high than on the low feeding level. It is, nevertheless, concluded that the equations presented in the paper can be used to estimate accurately the body weight of pre-pubertal (95-140-cm heart girth) Ayrshire heifers gaining 550-700 g/d.