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Karen Chaton wrote:
> I have another question. This time, about 'lysine'. Sounds like those of
> us who are feeding grass hays (or oat), are coming up short. How exactly
> would we supplement 'lysine'..specifically...
Hiya,
I've gotten several posts the past week about supplementing protein, so
I think it might be worthwhile to explain a little further about when,
where and why to supplement. Some of this is scientific fact, some is
opinion, both mine and that of some well-respected horsepeople both in
the academic community and out in the field.
The thing about feeding protein is that you don't just want to provide
quantity, you must provide QUALITY for maximum performance. When
nutritionists talk about "protein quality", this is what they mean.
Different sources of protein provide different amounts of the amino
acids that make up protein---one source may provide a high level of one
amino acid and almost zero of another, while a different protein source
may provide moderate amounts of two different amino acids, etc. Every
protein source is different. A "high quality" protein source is one
that supplies a good variety of several essential amino acids. If
you're feeding a horse only a limited ration, for example grass hay and
oats, then it is likely that the diet is deficient in one or more of the
essential aa's. The deficiency is increased if the feed quality is
poor, old or moldy---anything that destroys protein. (Though if you're
feeding moldy hay, you've got bigger problems that protein deficiency).
When talking about amino acids, you'll hear about the "essential" amino
acids---these are the one which cannot be synthesized by the body in
sufficient quantities, they MUST be provided as well in the diet. The
amino acid considered the first "limiting" in horses (and other species)
is lysine. It is the aa most likely to be deficient, and so if a
horse's ration contains sufficient lysine, it is almost certainly going
to be sufficient in the other essential amino acids, as well.
So why do sufficient aa's make a difference? Think of each amino acid
as a different letter of the alphabet, and proteins as words. In order
to make a protein (a word), you have to string together amino acids
(letters) in a certain order---if you don't have the right letter
available at the right time, then you can't substitute another letter
and still get the same resulting word/protein.
So if a horse's body is trying to respond to an increased workload, one
of the many things he has to do is synthesize new muscle tissue, more
metabolic enzymes, more blood cells, more regulatory hormones, etc. etc.
All of them proteins. If there is an insufficient supply of a
particular amino acid, then the protein in demand simply won't be
synthesized and the horse will not perform up to his maximal potential.
Here's where we get to the opinion part. Alot of people both in the
scientific community and out in the field are of the opinion that the
NRC recommendations for protein for a working horse are on the
conservative side. Not by a whole lot, but a few percent---in other
words, lots of people feel that intensely exercising horses do better
with a protein content closer to 12-14% rather than the 10% recommended
by the NRC. I happen to agree that a LITTLE extra protein
supplementation can make a difference, as long as the amino acids
supplied are the right ones. Here's the problem---first of all, there's
damned little information on what feeds provide exactly what amino acids
in what percentage. There's information on some of the protein
supplements, but it would be helpful to know what was deficient and was
wasn't in the diet to begin with. All the data simply is not available,
so it's hard to identify whether a particular ration is really deficient
or not. Deficiencies have to be identified qualitatively rather than
quantitatively and that's often hard to do.
The second problem is that equine research hasn't come even close to
catching up with the amino acid research going on in human exercise
physiology. There is increasing evidence to support theories that
careful supplementation of some specific amino acids might be very
beneficial to performance, but so far, science is pretty clueless as to
the details. As an example, alot of people feel DMG is beneficial,
which is simply supplementation of a form of the amino acid
glycine---but so far, there's no proof positive, just alot of
conflicting data (some of it mine). There's also alot of speculation
about some of the branched-chain amino acids, but again, nothing
concrete beyond some promising data from the field. Maybe Tom can
comment on this, I know he has some experience with aa's on the track in
this area.
Eventually, there might be some solid information as to exactly what
amino acids are required in what quantities for maximum performance, but
for right now, the best science can do is to recommend that a good
variety of protein sources be made available so that (hopefully) enough
of the right amino acids will be available when called for in response
to increased exercise demand.
So here's the deal with supplementing protein for endurance horses.
This, of course, applies to mature horses, not growing, pregnant,
lactaing or otherwise reproducing horses, all of which are a whole
'nother ballgame. Horses that are being fed more than a few pounds of
alfalfa, in addition to whatever other grass hays and grains in all
liklihood do not need protein supplementation---alfalfa has it's
downside, but it is a good source of alot of the amino acids. If you
live in an area that grows alfalfa without the high Mg levels we have
here in the SW, thank your lucky stars. That doesn't mean feed a ton of
it, just a five to ten pounds along with a good grass hay is plenty. If
you're in the SSW and enteroliths are a concern, then you can minimize
the alfalfa and supplement the protein (which is what I do with my own
horses).
If you're feeding your horse alot of good quality bermuda or other grass
hay, then according to NRC data, he's probably getting more or less
sufficient lysine at maintenance and only short a few grams at moderate
levels of work. Nobody's going to drop dead if you choose not to
supplement, but it also just might boost performance a bit if you did
supplement just a little. This is where you should keep everything else
in the diet as is, try adding just a bit of good-quality protein and see
what happens. Improvements to look for would be an increase in lean
muscle mass, improved hair coat and hoof quality as well as improvements
in performance itself---in endurance horses, look for slightly better
recoveries, maybe lower heart rates, longer time to fatigue. Most
endurance people know their horses well enough to know bright-eyed and
bushy-tailed when they see it.
More is not better, by the way. Boosting protein levels up too much has
deletorious effects as well.
So far, the best sources of high-quality protein are still the oilseed
meals, such as soybean, linseed and cottonseed meal, and milk replacer
pellets, such as Foal-Lac. Of the oilseed meals, soybean has the best
amino acid balance, and is very digestible (the amino acids are readily
available for absorption, not otherwise bound up as they are in some of
the grains, such as corn). Because soybean meal is VERY high in
protein, usually around 44%, it doesn't take much to supplement even an
intensely working horse. One pound will provide over 13 grams of
lysine, which should be plenty, without getting into excessive amounts
of nitrogen. Don't EVER feed whole raw soybeans, though, as the whole
seed contains a substance that inhibits the enzymatic digestion of
protein. The heat of milling soybeans into meal destroys this
inhibitor.
As usual, somebody asked me a simple question of what time it was and I
responded with a 300-page manual of how to build a watch. :-D Hope this
answered everyone's questions about lysine and protein supplementation.
Susan Evans Garlinghouse
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