A segmented line regression procedure to describe growth in beef cows.

Three segmented linear regression lines were fitted simultaneously to regress weight of Polled Hereford female cattle on age. Resulting parameter estimates from the procedure measure size and rates of gain. Sire and year of birth had the greatest effects on growth traits before growth rate slowed when heifers were approximately 17 months of age but had less effect in later life. Genetic correlations between weights at all ages were positive, as were genetic correlations between degrees of maturity at all ages. Animals taking longer to reach mature weights had greater mature weights. Degree of maturity and weight were positively correlated at a given age, but changed to negative as the age interval between weight and degree of maturity increased. Animals more mature at any age grew slower until they reached full maturity.