Re: NRC Minimum Requirements vs. Optimum

Eleanor Kellon, VMD

--- In EquineCushings@..., "pposey09" <pposey@...> wrote:

Hi all,
I am feeding my horses the minimum requirements to function in maintenance.

Why are we not feeding optimum requirements? Are optimum requirements published?
Optimums aren't known - and very few people look for them! Minimums are set by balance studies, which strive to find the level that keeps the horse from losing more mineral (in manure, urine) than is being taken in. To get optimal, you would have to study a key biochemical function of the mineral. For example, a key antioxidant system in the body involves the enzyme glutathione peroxidase (contains 4 selenium ions) and glutathione, which accepts oxygen free radicals. In humans, taking higher than minimum doses of selenium increases levels of glutathione until a ceiling is reached and higher doses have no further effect. That ceiling dose would be optimal. Glutathione production requires the amino acid glutamine. Similarly, glutathione levels will rise until a ceiling is reached.

Requirements for the major minerals are at least based on building body tissues for young animals, but then revert to minimums based on balance studies. I shoot for 150 to 200% of minimums for all minerals.

Eleanor in PA
EC Co-owner
Feb 2001

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