Thanks for the replies. They've never had lambs and certainly won't be now! Poor grazing is the problem, the field they're in is really lush and needs to be continually cut to keep it down, but it just hasn't stopped growing. I was hoping they'd lose some condition over the winter but with it being mild the grass just kept on growing and so did they! They don't have any other feed apart from a few odd cabbage leaves. I think I'll just have to fence off a very small area and try that. The only drawback is it'll get covered in droppings, so I'll be out poo picking no doubt!