There are some claims that various minerals may prevent coat bleaching, but as far as we know there has been no scientific study evaluating the effects of various mineral supplementations on coat bleaching. The best remedy to prevent coat bleaching is to keep the horse inside during daylight hours and turn it out at night. However, this may not be an option for many horse owners. There are various sunscreen products on the market for horses. Experience with these products shows that they do help the situation but may not prevent bleaching altogether. However, in Northern locations, these products may be more effective with the decreased sun intensity. You also might try turn-out sheets which block UV rays (and insects) while allowing air circulation to the horse's body and/or coat color enhancing shampoos for horses. Finally, to keep the horse's coat healthy and shiny, make sure that it is receiving a balanced diet and that its coat is kept relatively clean. Curry the horse regularly to distribute coat oils and remove dead hair. However, keep shampoo and soap use to a minimum because these tend to strip oils from the coat. Use plain water to cool and clean the horse after work, and save the soap for when it is really needed.