ridecamp@endurance.net: Re: Alfalfa and enteroliths

Re: Alfalfa and enteroliths

Susan Evans Garlinghouse (suendavid@worldnet.att.net)
Wed, 22 Oct 1997 20:43:25 -0700

MS DENISE G JOHNSON wrote:
A cantaloupe size enterolith ended his life. He was on alfalfa only.
<snip> The
> more questions I asked the more confused I became. One Vet would
> tell me it was Calcium in alfalfa. Another said it was the
> Phosphorus <snip>
> Another implicated Nitrogen. I've read the cautions about feeding
> wheat bran in the SW as it has been associated with stone formation
Now reading Susan's latest post Magnesium is added to the list. One
underlying thread I've concluded is
> stone formation is not well understood.

Hiya Denise,

What is NOT yet well understood is why some horses grow enteroliths like
crazy and other horses on the same diet never will. Also what
management practices will have an effect on enterolith formation, such
as feeding apple cider vinegar, oranges, what effect mineral source has
on formation and why enteroliths are more prevalent in Arabians than
other breeds. Otherwise, what IS very well understood about enteroliths
is that their composition is primarily ammonium magnesium phosphate---in
other words, ammonia from nitrogen, magnesium and phosphorus. Some sort
of matrix, called a nidus, is required for the mineralization to form
on---a penny, stone, hair mat, bit of tough stem, etc. There are other
nit-picking factors that may contribute, such as the fact that phophorus
from plant material is not as available for absorption as inorganic
phosphorus and therefore a high phosphorus content in the gut isn't
absorbed, it stays in the gut to contribute to enteroliths. Which is
further affected by data that probiotics affect phosphorus absorption
and utilization as well. But, as I said, that's fine details that
doesn't change or distract from the fact that phosphorus IS a
contributing factor in enteroliths, as are nitrogen and magnesium.
Period, unquote.

I have never heard of calcium being implicated in enterolith formation.

Alfalfa is a legume. On
> its' roots are nitrogen fixing bacteria.
> Nitrogen is supplied to the plants via this symbiotic relationship.
> Rarely is N applied to an exsisting alfalfa stand. So farmers do not
> supplement their stands with N.

Nevertheless, alfalfa crops commonly test out with crude protein levels
between 15%-20% or higher. Protein is nitrogen and that nitrogen came
from somewhere, supplemented by the grower or not.

Phosphorus is applied at least
> yearly since every ton harvested depletes the P needed for growth. P
> is very expensive and only what is needed per ton harvested is
> applied.

Alfalfa is not particularly high in phosphorus compared to other feeds
such as brans and cereal grains, so is therefore of lesser importance as
a source of phosphorus.

Potassium is not applied that I know of. Calcium, Sulfur,
> Magnesium, Iron, Selenium,
> etc. and other micronutrients are not applied that I know of

Only magnesium is implicated in enterolith formation and it doesn't have
to be supplemented, SW soils are already (variably) very high in it,
depending on the area. This is, after all, reclaimed desert and
therefore alkaline soil, and if it hadn't been for George Chaffey, the
only crop that would be growing in the Imperial Valley would be alot of
scrub and joshua trees. The alfalfa plant apparently has the ability to
concentrate magnesium (I don't know the exact pathway, I took Botany
instead of Soil Science :-), therefore higher magnesium in the soil
means higher magnesium in the alfalfa plant.

Susan I would like to know more about your
> info on Mg causing stones and it's naturally occuring high % in the
> SW soils. Does the SW also include AZ, Fallon NV alfalfa, Scott's
> Valley alfalfa in No. CA too? Could the salt laden Colorado River
> water be a factor?

It took me a few days to find an actual reference because when I asked
in the College of Ag, they all looked at me like I was out of my mind.
Around here, it's considered an elementary fact of life taught in
freshman Feeds and Feeding classes that enteroliths are made up of N, Mg
and P. However, it is also discussed as such in Proceedings 181 of the
Nutrition Society of Australia, in Current Therapies in Equine Medicine
-2 under Enteroliths and Small Colon Obstructions, in Equine Diagnostics
and Therapeutics (proceedigs of the 10th Australian Equine Vet. Assoc.,
1988) and at least three of the lay nutrition books on my personal
shelves (everyone that even discussed enteroliths) without delving into
the Cal Poly libraries.

The data on high Mg levels I got piecemeal some years ago from upstairs
in the Agronomy department, but the data is also easily available from
county extension agents. This isn't top secret info.

Exactly what precise areas in the Southwest are higher or lower in Mg, I
don't know. If I was buying someone's entire crop to feed to my own
horses, I guess I'd be more interested in specifics of how high the
mineral content is at such-and-such and address. My point in posting
the article on enteroliths is to point out a relationship between
regional mineral contents and enteroliths, since obviously all of the
alfalfa in an area is going to be fed somewhere, so that horseowners can
make an informed decision about their own management practices.

Whether mineral content from the Colorado River is a factor, I don't
know.

I couldn't bear to look at the stone they
> removed from my little guy in the vet's office for a few years now.
> Just the other day I did look. I know it could be analyzed.

Sure it could. And it will 99.999% sure analyze out as nitrogen,
phosphorus and magnesium. Not a big mystery.

I sincerely hope someday we will know
> exactly how to prevent stone formation

Well, we have a clue. Don't feed excessive amounts of nitrogen,
magnesium and phsophorus.

and still be able to feed
> alfalfa, because face it, the horses love it

Sure they do. A nice fat slab of prime rib also tastes alot better to
me than a bowlful of oat bran and a sliced banana, but that doesn't make
prime rib the healthier choice. My horses love alfalfa, too, but I'm
supposedly the more intelligent creature here and if I'm going to force
my horses to live under unnatural conditions (anything other than
free-range), then it's my responsibility to feed them in a way to
maintain their health. Begging for goodies or not, they also happily
eat a healthier ration of bermuda and intelligently chosen concentrates
and I don't have to worry about someday trying to find the $5000-7000
for enterolith surgery.

Susan

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