Sheep have fabulous insulation, they can stand a lot of cold, provided they’ve got plenty of forage. It’s the wet stuff that does the damage. So unless it’s unrelentingly wet, personally I wouldn’t think barren native ewes in Lincolnshire need any hard feed, but maybe a mineral lick or Himalayan rock salt would be a good idea. A little extra feed for ewe lambs won’t go amiss, especially in a hard winter.
If feeding hard food, don’t be on-off with it. Their digestions have to adapt, so feeding it just when the weather takes a turn is almost counter-productive. If you will need it when the weather is bad, get them on it sooner and keep them on it until the bad weather has passed. Once a day is best for sheep, IMO. Always with ad ib forage, of course.
The above is one reason we’ve switched to grass nuts. No change to digestion needed, or very little. We use the Dengie All Stock ones.
We’re in North Cornwall though. I’d have tried the grass nuts in Cumbria if I’d known about them, but I can’t say if I’d have been as pleased with them in that more severe climate.
I always fed a 16% all stock ration through winter to all my sheep up there, btw. Just maybe 1/4lb a day a head for the native types. So far down here I haven’t fed any nuts this year, and the pregnant sheep are doing fine. I’m in two minds about feeding for the final two months; maybe just the first timers (who went to a Heb tup; the others went to a Romney so I don’t want lambs growing too large) and the Zwartbles
. The hoggs may need a bit of feed if the evil wet weather continues; they don’t have the reserves the older sheep do.