MSM, Brewer's Yeast and Biotin! All great for hair, skin, teeth, and soft tissue
they're all perfectly safe supplements - all my horses get it for regular upkeep. My mare has a habit of rubbing her mane out but this year on those supplements it grow in long thick and wavy! You may notice their hooves grow faster too though - my pony suddenly started needing his feet trimmed more often when he got on it.