diet

Question
My friend's horse has a problem. When he is in the stable and has finished eating his food, he starts eating the sand (bedding) from the stable. She has bought him a mineral lick block but this only worked for 2 weeks and then he went back to eating the sand.
She originaly had 2 horses but her other one died from a twisted gut after having serious colic from eating the sand from the stable.
She thinks that he may be lacking something from his diet. The horse is out in the paddock, eating grass all day and then is brought in at night and is fed oaten hay, chaff and coolmax(pellets).
Could you please advise us on what to do?
Thank you.

Answer
IT IS PROBABLY SOMETHING LACKING IN THE DIET, BUT UNLESS A BLOOD TEST REVEALS WHAT IT IS, YOU CAN GROW OLD TRYING TO FIGURE IT OUT.

IN THE MEANTIME, GET ONE OF THE PRODUCTS ON THE MARKET TO ADD TO THE FEED TO KEEP HIM FROM GETTING COMPACTED FROM THE SAND LIKE HER OTHER HORSE