Sheep are classified according to the strain of their parentage. Like a collie dog or a Siamese cat. Sheep get graded these days primarily for food production. So speed and quality of meat are the main factors considered. Few breeders or farmers work towards good wool production, again money dictating how much effort is viable.
The reason for this bountiful supply of cross breeds is simply that they are the dominant meat sheep.
They are called hybrids rather than crosses, this is because the lineage is designed quite specifically to include mixed grandparents. So, an example of a cross would be Texel crossed with Dartmoor Whiteface.
A Hybrid sheep might have a Texel ram and a Dartmoor Whiteface mother on the ram’s side, and a mother who is herself a cross with specific parentage. Those two crosses then cross to make a hybrid, often with more vigorous growth.
Sheep produce hair, which is keratin, the same as you and I might. And, like us, sheep can have off-days.
Keratin is pure protein and is built, along with the rest of the sheep, from grass. Grass in turn gets energy from photosynthesis, and uses that energy to convert mineral salts in the soil into fleshy green leaves.
As you know, the climate in the UK is changeable. And so is the grass.
Each change in the weather heralds a change in the growth rate (and nutritional content) of grass. Each change in the rate of growth makes a potential break-point in the hair.
Shepherds put a lot of thought into where they graze their sheep. Too much energy results in grass that is too rich for the sheep and will make them ill. The protein in grass is converted by the sheep into its body and hair.
A drop in protein caused by poor soil will result in a break in the wool, a weak spot. A thread is only as good as its weakest length, a problem only partly solved by spinning.
Despite this, and despite the seemingly high price of wool, very few shepherds will be attending to wool production with anywhere near the same vigour as they would (quite rightly) monitor that the flock isn’t getting too much spring grass.
After slaughter a raw sheepskin is worth just 50p right now in Britain, not enough to put any thought in. Indeed, most sheepskins are destroyed the same day the meat is cut.
When a sheep is in a field with its freedom constrained it will eat what the shepherd has has made available. Contrastingly, sheep kept in the open landscape will eat what nature has made available. Dartmoor flocks do sometimes have to be rounded up and tagged or treated, maybe even brought inside for extremes of weather, but snow permitting they do get to graze on herbs and roughage along with the sweet spring shoots of an ungrazed tuft. On Dartmoor the sheep control their own rate of growth – and the weather acts as a natural prompt for good hair growth.
In conclusion then, when it’s cold outside and you have a huge wilderness of varied grazing and roughage, your sheep will always be having a good hair day.