OK, after my horse being utterly vile in his behaviour over the weekend, I kept him off the grass and hey presto - he's much more like his usual self today. So, that answers that - however, he needs sometime at grass doesn't he? So, if I put him out on the grass for say 4 - 5 hours a day, rather than the usual 14, will that be sufficient? Of course, hay will be available outside of this for him. He is soooo complicated!!!!!!!!!