GENETIC TRENDS AMONG SIRES AND DAMS IN RECORD OF PERFORMANCE TESTED HERDS

A total of 61,688 Hereford and 22,333 Aberdeen Angus calf growth records from Record of Performance tested herds were studied to estimate annual genetic trends among sires and dams and annual trends due to length of time on test (environmental trends plus residual genetic trends not accounted for by trends in sire and dam genetic merit). Average annual genetic trends of dams were 0.27, 0.0012, 0.64 and 0.0044 kg for weaning weight, preweaning average daily gain (ADG), yearling weight and postweaning ADG, respectively. Annual genetic trends in average sire merit were 1.74 kg for weaning weight, 0.0084 kg for preweaning ADG, 2.60 kg for yearling weight and 0.0065 kg for postweaning ADG. Trends due to length of time on test were 0.53, 0.0027, 1.51 and 0.0062 kg, respectively, for weaning weight, preweaning ADG, yearling weight and postweaning ADG.