Hi Agri You will need to put more effort into getting a ewe to adopt a strange lamb. Her natural instinct will be to reject it as it doesn't smell right, and to the lamb the new ewe doesn't sound right - it has been listening to a different ewe for months from inside, so neither will immediately recognise the other.
One way of getting a ewe to adopt a strange lamb is to rub it in the dead lambs afterbirth or to put it in a bucket with the dead lamb and stir them about until the new lamb smells of the old. Or you can take off the skin of the dead lamb and put it on the new lamb like an overcoat - this is more likely to work if the dead lamb lived for a while and was cleaned by the ewe. This method is useful too if the new lamb is a bit older so already on its feet - the skin will make it fall over a bit. If those methods don't work you can tie the ewe with a head collar and place bales to stop her kicking the lamb, then supervise feeding.