 |
[RC] Blood test levels - Eleanor KellonIs this 200 to 250 target for serum, plasma or whole blood Se? Whole blood runs 25 to 28% higher. I assumed (?) the test results posted were serum because E was tested.
It's known in other species and confirmed in horses (KER) that exercise causes release of Se from red cells and subsequent increased urinary excretion. Like most nutritional studies, this was done using thoroughbreds so tells you nothing about an endurance horse's needs, i.e. with prolonged exercise, but there's a strong possibility that losses increase as exercise duration increases, attenuated somewhat by decreased urine production.
Just a word about Se yeast. I'd be cautious about assuming there is a greater safety margin with Se yeast. True story. Mature Icelandic horse (light use), living in New England, selenium deficient, started on 2 mg/day of Se yeast. Horse moved to Colorado. Selenium supplementation continued at the same dose. Within six months, mane and tail falling out. Forage was tested and contained 0.5 ppm Se. Horse was getting maximum of 15 pounds/day for an intake of organic Se from the hay of 3.4 mg/day from this source, 2 mg from the Se yeast, no other Se supplemented items in the diet. Se yeast stopped. Hair regrew. Unfortunately, she didn't get Se testing on the horse but it was seen by a vet, no skin pathology/infections found and hair regrew after stopping the Se yeast.
Organic seleniums are better absorbed and better retained in the tissues. This is offset to some extent by incorporation of chelated forms into structures where the Se ends up being sequestered and nonfunctional but there's still the potential for toxicity. In this sheep study:
the safety margin for acute toxicity with selenomethionine was 2 (4 mg/kg/day vs 2 mg/kg/day for sodium selenite). The organic selenium was not associated with the same degree of oxidative stress (by indirect measurement, vitamin E) but substitution of Se for S in tissues apparently occurs in a similar fashion and symptoms of toxicity were the same.
The same KER study that documented increased urinary loss with exercise:
showed increased absorption and retention of Se yeast, similar to the sheep study.
Performance horses likely do need more Se, almost definitely do, but there's a good chance not all performance is equal.
Eleanor
-- Eleanor M. Kellon, V.M.D. Equine Nutritional Solutions 58 Maple Farm Road Ephrata, PA 17522
|