We're 7 weeks off lambing and I've just begun supplementing the ewes with an 18% protein ewe roll - 50g twice a day at first, to avoid problems with the rumen. I then increase in increments, depending on the condition of the ewe and how many she's carrying. A wether will happily munch away at anything you care to put in front of the ewes and put on too much condition, as well as butting them away and possibly causing damage to the in utero lambs.