Re: Protein and assorted questions

Susan Evans Garlinghouse (
Thu, 06 Nov 1997 14:22:58 -0800

Carol Harrison wrote:

> Exactly what level of protein should an endurance horse be receiving? If
> I'm feeding a 14% crude protein pellet, what is the digestible protein?

Digestibility of a protein varies greatly depending on the source of the
protein, the species eating it and the individual animal. As a general
rule of thumb, most protein sources used as animal feed are digested to
the extent of 75-80%. However, if you're worried about coming up with a
certain percent diet and are calculating how much protein is actually
being digested and absorbed by the horse, don't worry about it. When
the editors of the NRC recommendations came up with the suggested
protein levels (and the other nutrient levels as well), they took
digestibility more or less into account---so just base ration
formulations on crude protein levels and don't lose sleep over the
digestibility. This assumes, of course, the protein source you're
feeding the horse is a normal sort of horse feed, ie mostly plant
sources. Herbivores can digest some animal sources of protein, like
fish meal, but it can also cause tummyaches, so it's best to stick to
plant sources for the most part.

> Does an endurance horse running for top 10 need a different level than a
> horse in turtle position?

Yes, slightly. NRC suggests about an 8% crude protein level for horses
at maintenance, 9.8% for horses at light work and 11.4% for horses at
intense work---so it has as much to do with the horse's overall work
level as specifically how fast he's going on one particular day.

Dr. Ralston posted some good information on a study she did that
indicated that horses getting higher levels of proteins had higher
incidence of metabolic failures (that's poor recoveries, colic, tying
up, those sort of things) than horses on lower (8-10%) protein, so I'd
take that as a pretty good indication that Sufficient is Great and More
Is Not Better where protein is concerned. My own opinion is that
anything over 12% or so for mature endurance horses is excessive and
while not life-threatening, is certainly not adding anything to the
performance level. I also posted something about feeding a little
higher protein levels, but my own preference is around 11-12%, which is
still pretty low. My example in that post was the polo barn I did some
consulting for that showed a big improvement in condition when protein
was supplemented. Dr. Ralston and I have posted back and forth since
then and Dr. Ralston's opinion, which I agree with, is that those horses
were on an unusually nutrient-deficient diet that was more the exception
than the rule. So that example should just demonstrate that not enough
protein is also a bad thing, but shouldn't be used as an argument to
crank protein levels up to excessive levels.

Most horses (not just endurance horses) tend to be on a ration that is
excessive in protein and deficient in energy. The body can and will
burn excess protein as an energy source, but it's not as efficient and
has some by-products that can also carry some disadvantages---such as
increased urea/ammonia levels in the blood which according to some
studies may hinder energy production. Not to mention making stalls
really stinky and sweat really nasty and thick.

I posted something a week or so ago that talked about protein quality
and amino acids and all that---for the most part, feeding a low protein
ration is just fine, even preferable within reason, as long as the
QUALITY of the protein is good and therefore likely to provide a good
balance and variety of the essential amino acids. Most feeds are high
in one nutrient or another and at the same time deficient in some other
nutrient. A good way to ensure that your horse is getting a decent and
balanced variety of nutrients (and not just protein) is to feed several
different food sources. Human nutritionists will tell you the same
thing, that a varied diet is better nutritionally than eating the same
exact meal every single day. This doesn't mean you should feed your
horse a different menu every day of the week (and doing so would lead to
upset tummies), but it does mean that using a variety of feeds in your
daily ration, (such as bermuda/alfalfa/beet pulp/corn oil/oats/corn,
just for example) is almost certainly going to give you a better balance
and variety of nutrients, including protein quality, than will feeding a
ration that consists of only one or two feeds (such as oat hay and
corn). This isn't always the case 100% of the time, but most of the
time this will be true.

There is one more argument for feeding a somewhat varied diet, and this
is human nutrition principles being applied to horses. Nutrition is
still a relatively new science, compared to biology or chemistry or
physics. Alot of nutrients have been discovered just in the past 20
years or so and it's a good bet that there are still important
nutrients, or physiological roles regulated by nutrition, that haven't
been discovered yet. A good example are the anti-oxidants and their
role in protecting against aging (read "oxidation") that has been the
subject of research in the past few years, others are the rather elusive
properties of some foods to protect against cancer, heart disease, etc.
It's a good bet that horses can be affected by these beneficial
properties in some way or another as well and by feeding a varied diet,
the odds are higher that the diet may contain a measure of these
still-undiscovered-but-beneficial nutrients. On the flip side of the
coin, specific plant sources may also contain substances which may be
detrimental---so if your ration isn't based entirely on just one feed
source, any unknown detrimental substances are going to be diluted in
the varied ration. Just something else to consider.

OK, I just know Mike Sofen is up there in Washington adding this to his
list of Things To Lose Sleep Over, so I'm going to quit yammering on
now. Hope this answered the questions without hopelessly confusing

Susan Garlinghouse