EVALUATING RELATIONSHIPS AMONG BODY WEIGHTS OF CROSSBRED STEERS AND HEIFERS OVER TIME USING PRINCIPAL COMPONENT ANALYSIS

Data on 573 steers and 570 heifers calves born over a 4-year period (1994 to 1997) were obtained to describe and characterise growth of seven sire breeds raised in various management groups. The first principal component (PC1) accounted for 59 % and 75 % of the total variability among steers and heifers, respectively, was defined as a measure of overall size (weight at all ages). The second princip al component (PC2) accounted for 20 % of the total variation in steers and 10 % in heifers and contrasted pre-feedlot and feedlot growth (weight at specific period). Overall size as well as feedlot growth were significantly affected by the birth years, breeds and management groups. It was concluded although principal component analysis is a useful technique for studying body size over time, that these results indicated that some differences in growth patterns of diverse breeds using only body weights could not be detected. Hence, it was suggested to consider a wider range of traits such as body measurements