Growth Patterns of Angus, Charolais, Charolais • Angus and Holstein X Angus Cows from Birth to Maturity 1'2'3

Growth patterns of 182 cows [73 Angus (AA), 31 Charotais (CC), 38 Charolais x Angus (CA) and 40 Holstein x Angus (FA)] were studied from birth to maturi ty. Breed type significantly affected weight and condition at all ages. Crossbred cows were heavier than AA and lighter in weight than CC cows (P<.01) at all periods. Differences between CA and FA cows were small. The CA cows were somewhat heavier than FA cows, but when weight was adjusted for condition, these two groups reversed rank at 56 and 68 mo. Differences in weight among breed types increased from birth to 44 mo and stabilized thereafter. Weights at early ages were influenced more by environmental effects than were weights at later ages. Adjustment for condit ion significantly reduced phenotypic variation in weight at all ages. Two growth models (Brody and Richards) were fitted to the weight-age data for each breed type. Differences in growth were expressed in terms of differences in mature weight and maturing rate. The AA cows were smallest at maturi ty and matured most rapidly; CC cows were largest and matured least rapidly. The FA and CA cows were intermediate and similar in mature size and maturing rate. Crossbreeding may have increased maturing rate somewhat when weights were not adjusted for condition. The four-parameter Richards model did not