A four-year study was conducted in which a protein supplement was fed to Hereford heifers so that they could be first mated at 15 months of age and calve each year thereafter. Protein supplemented heifers had an ADG of 500 g during the winter and were at a suitable live weight for mating at 15 months while the unsupplemented heifers lost weight and were too small for mating. Supplemented heifers calved 12 months before control heifers. In addition, they had higher calving percentages in subsequent years when mated whilst lactating. Protein supplemented heifers also weaned heavier calves than the control group.