My goats love to rub themselves against straw, walls, fences ... especially when they are growing or shedding their cashmere undercoat layer - they are itchy but don't have paracytes - I think it is symptomatic of growing or loosing their insulating layer - also it is fun. BTW I've found it's best not to brush them when they have their cashmere undercoat so as not to remove their insulating layer in the cold months - even if they are start growing them in the summer, like mine are.