I had two horses with selenium deficiencies. The first presented as occasional cramping late into a ride, the second was a full blown tying up episode. In both cases, having the selenium checked and then supplementing was the first step to preventing another episode, along with regular exercise, little or no grain, and long warm-ups. The selenium dosage for the first 2 months was at least 3 grams daily! Not just the 1 gram suggested daily dosage. The reason is to get the levels built up in the system. I was told by vets, Heide Smith and Susan Garlinghouse and my own vet, that just supplementing with the label recommended dosage would not increase the blood level sufficiently. Either a shot was needed, then supplementing, or the 3-4 grams daily. I believe Susan Garlinghouse wrote that she supplements all her working horses with a few grams daily, even after their levels are sufficient. Many people are afraid to give more than the recommended amounts because it can be toxic, but unless your pasture or hay has high levels it is difficult to reach toxic levels with supplementing.
BTW, 19 yr old Shadow, who’d had a sever tie-up last June, completed a 50 about 18 weeks later. She missed Tevis because it was too close, and will be doing her first 50 this year next weekend.
“Most racing Quarter Horses, Thoroughbreds, Standardbreds and Arabians with tying-up, suffer from a separate disease from PSSM called recurrent exertional rhabdomyolysis (see RER information). In these breeds of horses, the accumulation of abnormal polysaccharide, the hallmark of PSSM, is rarely if ever present.”
