they did do when young but not too bad now.tbh its a mix of things i think.
they see the mother do it when they are young as she cleans up after them by doing this.
and also it can be down to an iron deficiancy(sp)

our girl has not done it in ages but we give them veg in thier food so they get it from there now too.and cod liver oil tablets are good for them.their coat and bones