Compudose® : its effects on the growth, offspring performance, lactational performance, and carcass characteristics of Hereford × Friesian heifers at pasture

This study investigated the efiects of Compudose w on growth, lactational performance, carcass characteristics, and ofispring performance of Hereford£Friesian (H£F) once-bred heifers (OBH) under pastoral conditions. Nineteen H£F heifers were implanted with Compudose 400 at 90 days of age (Compudose 90), 19 were implanted with Compudose 400 at 210 days of age (Compudose 210), and 19 were not implanted (control). Neither Compudose group difiered signiflcantly in liveweight from the controls. However, there was a tendency for the Compudose 90 group to be slightly heavier, and the Compudose 210 group slightly lighter, than the controls so that the only signiflcant difierences in liveweight were between the two Compudose groups. Similarly, there were no consistent efiects of Compudose on measures of body or skeletal size. The efiects of Compudose on carcass characteristics were small and related mainly to a tendency for increased muscling. Compudose delayed conception slightly but had no efiects on calf birthweight. However, calves born to control heifers were 15¢3 kg and 16¢2 kg heavier ( P< 0 ¢05) at weaning than calves born to Compudose 90 and Compudose 210 heifers, respectively. Most of this difierence in liveweight was established by Week 4 of lactation. This implies that Compudose treatment inhibited milk production of the dams, particularly in the early part of lactation, an efiect not detected by the weigh{nurse{weigh (WNW) method. Implanting heifers with Compudose at 90 or 210 days of age is unlikely to be beneflcial, both because it has little positive efiect on liveweight gain or carcass characteristics and because it may inhibit lactational performance.