Calfhood weights, body measurements and measures of fatness versus criteria of overall size and shape for predicting yearling performance in beef cattle.

Data were collected over a period of 4 yr from bulls and heifers of two location-breed groups (East Tennessee-Polled Hereford, Cumberland Plateau-Angus). Variables measured and recorded at the time all calves were weaned (at an average age of approximately 230 d) were age (in d at time of data collection; AGE), weight (WT), visual condition score (COND), ultrasonically measured subcutaneous fat thickness (FAT), body length (LT), heart girth (HG) and hip width (HIP). These variables were included in principal-components (PC) analyses. The first principal component (PC1) was a measure of overall size, accounting for 66 to 69% of the total variation. Remaining principal components contrasted body shapes. Stepwise multiple regression analyses (separate for each location-sex subgroup) were conducted using various combinations of the weaning variables listed above, or principal components of these variables, to predict birth to yearling average daily gain (BYADG), weaning to yearling average daily gain (WYADG) and yearling condition score (YCOND). Condition score (COND) appeared to be the most valuable complement to AGE and WT, with LT somewhat useful also. In equations including principal components, after AGE, PC1 most frequently entered first, generally followed by PC2. Coefficients of multiple determination (R2) were largest for BYADG (greater than .50), followed by YCOND (.15 to .50) and WYADG (less than .15). Longer-bodied, thinner-fleshed animals of a given age and weight tended to have larger gains and smaller YCOND.