The introduction of the hormonal implant,oestradiol - 17 β in a slow release form (Compudose 365 Elanco) offers the benefit in an “18 month” beef system of improved live-weight gain of steers at grass, continued during the final finishing period without further handling and cost. In this trial the persistence of the benefit over a 12 month period and of any interaction with the level of protein fed in the compound diet during the last 4 months of winter feeding was examined.