As FW says the hebs eat selectively and like to browse we have a field with an area of longer grass and the hebs are choosing currently to eat the seed head s off the longer grass rather than.the green clover they also like to browse nettles docs and bizarrely thistles
BL
Yep - Hebs and other primitives, maybe all sheep, are good at choosing a 'route' for going around their available grazing/browsing area, so they take a bit of this and a bit of that. A bit like goats with a range will do.
Ours tend to eat certain things at certain times of year. For example, they don't like mid sized nettles, which maybe sting more viciously than the younger and older nettles, but I have noticed that from about now onwards, as the nutritional content of grazing declines, so they eat more nettles, thistles and browsing in general.
we currently have one multi-horned Heb ewe lamb, number 93, who loves browsing on the hedge and the rough grass and herbs under it. To get to it she has to stick her head through the Rylock mesh, then of course she can't pull it back through. She has already broken 3 of her 4 horns this way. She bawls very loudly when she's stuck, so Mr F and I just say the magic words "93" and trog off to free her. It's a wretched nuisance in fact, but she's becoming quite a friendly sheep this way.
There are certain times when the Hebs aren't all that keen on the longer, dryer grass amongst the lusher stuff. I think that when the ewes are feeding their lambs they know they need richer feed than once they wean them, so you can't run both Zwartbles and Hebs together and expect one to eat only lush grass and the other to eat only coarse stuff - they will both eat both, but in slightly different proportions.
So don't calculate your stocking rate as if only each breed will be there - you have to take into account the total number of grazing units (1 grazing unit is one cow or 5 sheep).
But no, Hebs will not eat only the lush grass leaving the Zwartbles hungry.