It depends how good your vets eyesight and patience is for how old, I do mine as ram lambs as its easier for me. We tell people not to use them for six weeks... but tbh they are probably near infertile with near immediate effect
Why not buy one of mine? Non-mv ram lamb (not used/tested) £120 non-mv ram used/proven (no early pregnancies) £150 or mv acc. proven ram £200