LINEAR BODY MEASUREMENTS OF CATTLE BEFORE AND AFTER 20 YEARS OF SELECTION FOR POSTWEANING GAIN WHEN FED 2 DIFFERENT DIETS

At weaning and again after postweaning gain tests, height and width at hips, height at withers, body length, girth, head length and width, m uzzle width, and cannon bone circumference measurements were obtained from Angus and Hereford bulls and heifers born in 1964, 1984, and 1985 (n = 989). The cattle were from the initial and final two calf crops selected for postweaning gain when fed either a high-concentrate diet or an all-hay diet. Analysis of variance and canonical discriminant an alysis were used to examine the relationships among body measurements and major sources of variation (breed, year of birth, sire within bree d and year, diet, sex of calf, age of dam, and the regression on age o f calf). Canonical discriminant analysis indicated that ore underlying variate explained nearly 90% of the total variation among the weaning measurements, whereas three variates were required to account for tha t proportion in the end-of-test measurements. At both measurement time s, the first canonical variate was, associated with year of birth, the second with sex of calf, and the third with dietary energy. Correlati ons between each canonical variate and the original body measurements indicated that year of birth (variate 1) was most closely associated w ith body length and cannon bone circumference at weaning and with body length and height at hips (but not withers) at end of test. Sex of ca lf (variate 2) was associated most closely with width of muzzle and he ad. Diet (variate 3) was associated with heart girth. Faster-growing c attle were longer in body, but not necessarily taller.