Published online by Cambridge University Press: 06 May 2016
It is now widely accepted that the subcutaneous implantation of stilboestrol or hexoestrol increases the rate of live-weight gain in lambs and cattle. In sheep it is generally considered that for a feeding period of up to 12 weeks a single implantation of hormone produces an adequate growth response. Perry et al.(1951), Stephens & Thompson (1952) and Bell et al.(1954) reported no advantage from repeated implantations during the experimental period. In a series of experiments at this Institute (Preston & Gee, 1957a) it has been noticed that the major part of the increased weight gain takes place during the first six weeks after hexoestrol implantation.