662. The comparative efficiency of some methods of estimating the live weight of dairy cows

Abstract

1. Data from 133 Dairy Shorthorn cows in three herds have been used in a study of various methods of estimating live weight from body measurements based on logarithmic relationships and indices of body volume.2. Regression equations are presented relating live weight to several combinations of chest girth, paunch girth, length of body and age.3. The most satisfactory estimate of weight from a single body measurement was given by the regression of log live weight upon log chest girth.4. Appreciable increases in the efficiency of estimation were obtained by including log paunch girth or log length of body as second variates in the regression, and a further increase by including them together.5. Indices of body volume using chest girth and length of body, or chest girth, paunch girth and length of body gave good estimates of live weight, and there was very little difference in efficiency of estimation from that when the three measurements were used in a logarithmic regression.6. The effects of the addition of age to regressions involving chest girth, paunch girth and length of body were slight but statistically significant.7. The most satisfactory practical method of estimation using the three body measurements is given by the equationLive weight (lb.)=0·000935 LB(CG2+PG2+ PG.CG)+57 (all measurements in inches).8. Comparison of fiducial limits showed that these covered a range 4–5 times as great for live weights estimated from chest girth than for live weights determined directly, and that the inclusion of length of body and paunch girth reduced this range by 25–30%.