I picked up King’s test results a few days ago. These are the blood tests that were done a few days after Aprilfest. All of his electrolytes were in the lower part of the normal range. Selenium was also low/normal. But barely. The reference range is 0.12 – 0.18. His level was 0.12. So he’s right on the cusp of being deficient.
I’m still waiting on the results from last Sunday. He had blood taken right at the time of the pull (when the cramps first hit), and then again four hours later. So that will be interesting to see.
But for now, I’m treating him as selenium-deficient. It would make sense. All the other horses here get some sort of supplemental feed, so they are getting selenium in that, in addition to whatever they get in their supplements. Due to his weight problems, King gets only hay, and a handful of beet pulp or roughage chunks to mix his supplements into. And because I was being conservative about selenium, he was only getting a maintenance dose of that. I’ve been reading madly on selenium over the last few days, and given his workload over the last six months, he really should have been getting double that. At least. The symptoms fit too.
I’ve searched for commentary from endurance vets online, and found that most of them are recommending that endurance horses have selenium blood test values in the middle or high end of the reference range.
I have now switched him to an organic selenium, instead of the selenium salt that most supplements use. It’s supposed to be much more bio-available. It’s going to take a while to get his levels up though.