Effects of oestradiol-17β on growth and insulin-like growth factor I of steers on different pasture allowances

Abstract We have studied the long-term effects of oestradiol-17β on growth and plasma concentrations of insulin-like growth factor I (IGF-I) in steers. One hundred 6-month-old Angus weaner steers were randomly allocated to two grazing groups at stocking rates of 3 ha −1 and 5 ha −1 . Half the animals in each grazing group were treated with an implant of oestradiol-17β. High stocking rate (HS) steers had lower liveweight gains and lower plasma concentrations of IGF-I than low stocking rate (LS) steers. Oestradiol treatment stimulated liveweight gain at both stocking rates ( P P