Growth patterns of Belgian Blue replacement heifers and growing males in commercial farms

A survey was carried out to propose models of growth curves in Belgian Blue cattle less than 20 months of age and raised in commercial farms in southern Belgium. Live weight data were recorded between 1993 and 1999 from 1104 breeding heifers, and 924 growing males. The linear, polynomial group, power, logistic, Brody, Gompertz, von Bertalanffy and Richards models were used and compared. A step-wise linear growth model characterized by two periods of linear growth was also evaluated. This last model has been proposed as the reference model to characterize the growth curves of Belgian Blue cattle less than 20 months old. The animals were then ranked and divided in subgroups based on percentiles and quartiles in order to compare their performances. The subgroups performing better presented a greater homogeneity. The males ranked above the 90th percentile presented a growth rate comparable to that of young males selected for artificial insemination. Cattle ranked above the third quartile presented a growth rate comparable to that of licensed animals. When reproduction performances were related to the growth rate, it appeared that the better growing heifers were bred younger and heavier than lesser performing animals.