III. Growth and reproduction of straight-bred and beef-cross Friesian heifers

Abstract Growth and reproduction data were obtained over 4 successive seasons from 885 heifers grazed in one environment from 4 to 22 months of age, after being reared on 16–21 dairy farms. Breeds were Friesian (F × F), Hereford (H × F), Simmental (8 × F), Angus (A × F), Limousin (L × F), South Devon (SD × F), Blonde d'Aquitaine (BA × F), Red Devon (RD × F), and Charolais (C × F). Some Angus (A × A) heifers from a different source to the other animals were also included. F × F heifers consistently had highest growth rate, earliest puberty, and greatest oestrous activity, contrasting particularly with the European breed crosses which were older and heavier at puberty. The British breed crosses were intermediate in these characters between the F × F and European breed crosses. The A × A had least oestrous activity of all breeds. Although breed differences in pregnancy rates at 2 years of age were not as marked as those in previous oestrous activity, it was concluded that, in a seasonal mating system for yea...