Endurance.Net Ridecamp Archives

On Feb 8, 2008 10:32 AM, <heidi@xxxxxxxxxxxxxxx> wrote:

> I wondered about that too. Found a survey of trace elements in Icelandic
> forages. Coastal and mountainous areas are adequate at 0.1 to 0.2 ppm,
> otherwise low.

Considering that we are looking for an overall dietary average of 0.9 ppm, calling that "adequate" is a bit odd...  Sounds like if the rest is lower, they have indeed been selected in an area that is pretty darn deficient.

 

There are very few places in the world where forages are ever going to average that high. What is adequate or ideal for endurance is likely very different from other classes of horses. Adequate boils down to what is required to keep blood levels within a normal range and prevent deficiency, including less obvious effects like suboptimal fertility and immune function.

> Had another client with an inactive horse (recovering laminitic), forage
> selenium tested and virtually undetectable, full size horse this time (Arab
> cross), put on 3 mg/day Se yeast and serum selenium came back 190 (high for
> serum) a year later. This is well below anything toxic but surprising. Might
> have been a post feeding peak, but it's difficult to get serum Se over 160
> or so with selenite.

Depends on the horse.  In practice I saw quite a variance in responses to oral intake in terms of how much it took to get them into a "normal" range (and no, 160 is not "high" even for serum--given what you've said about the differences between serum and whole blood, that's just a good normal, given that normal for whole blood is 200-250).  

 

The horse I was talking about was 190, which is high for serum. Again, far from toxic, but higher than what you would get with selenite for a serum level.

 

But I've never seen any go above normal (testing whole blood, where we would see it) even supplementing 7.5 mg per day on a long-term basis.

 

Are you talking about sodium selenite or Se yeast? Endurance horses or other classes? Even 7.5, for sodium selenite at least, is way below the suggested intake for chronic toxicity of 20 ppm, more than likely because the kidney can easily handle any overloads up to that level. However, all the research was done with sodium selenite and Se yeast appears to accumulate to a greater level than sodium selenite.

 

Eleanor

-- 
Eleanor M. Kellon, V.M.D.
Equine Nutritional Solutions
58 Maple Farm Road
Ephrata, PA 17522