[Alisongunn]

I've got a shearling Herdwick tup in with three Herdwick ewes. He showed great interest in them when he first went in with them in October but isn't showing any interest now. I'm hopeful that they are all in lamb, and they should be due approx end of March. My question is this...is it okay to leave him in with them, up until I bring them inside for lambing, or is that a big no-no?

[SallyintNorth]

The only risk is if one of them aborts or reabsorbs, cycles again, and he gets her back in lamb.  But with 3 ewes, and Herdwicks at that, that's a pretty small risk - and you would be aware, if one of them doesn't produce in March, that there is a chance she will lamb later on.

I only take tups away from in-lamb ewes if I want to feed them better than him, or if it's really important to me to have a definite end-date for lambing.

[twizzel]

You can do, but if you want to feed them leading up to lambing you’ll need to take him out. 4 weeks lambing is long enough for me so I always pull my rams out 

[shep53]

Remember not all feeds ( pellets / nuts ) are suitable for male sheep , it should say on the label

[harmony]

Herdwicks will be happier lambing outside.

[Fleecewife]

I would say to watch him closely if you leave him with the ewes.  Because their hormones are different at different stages of pregnancy, tups can get a bit aggressive with pregnant ewes, especially close to lambing.  As harmony says, Herdwicks should be lambing outside, but with the tup there too, they will get no peace and he might take to butting him.  So watch him and at the first sign of aggression then take him out or he could damage the unborn lambs.  And as others have said, there's the thing about not feeding tups the same feed as ewes.
For future years, you could keep back a wether to keep your tup company, then send him off once the following year's lambs are due to be weaned and keep another wether back.