One of the horses in which i go and train horses eats wood worse than a beaver... We originally had her in a paddock where a wooden roundyard was half built and there were large wooden posts in a circle. There are now no wooden posts left, just stumps of wood and the rest of the posts lying on the ground, literally eating beaver style! we now have her in a star picket and wire paddock, not wooden. she has now stopped this but did get sick at one stage as these posts had traces of poisons as they were treated pine. i was thinking she is lacking some nutrition? Maybe copper? And a few days ago we were about to go out and 2 other horses we noticed were just standing there just eating mouthfuls of sand. we put hay infront of them, even a hard feed and they wouldnt eat it, they just kept eating sand. we opened the gate so they would roam around eating grass around the property, i lead them out one by one and they literally trotted and cantered back to eat the sand!!!!! i know they must be lacking something like copper or iron? we do feed them a mineral mix called equimin.