There is a risk of mastitis in very cold weather in crutched out ewes but I think the risks of strike outweigh the risk of mastitis. I crutched all my little flock last year pre lambing with no mastitis issues and this year the girls that needed it post lambing were crutched- the only one to get mastitis was a milky lleyn that hadn’t been crutched. We are very prone to strike here though, it’s damp and very mild in Cornwall... so I’d rather keep them trimmed and tidy to reduce strike. Last year we had our first (and only) case of strike first week of May before the ewes were shorn.