Definitions and a time out

[Sarah Ralston <ralston@AESOP.RUTGERS.EDU>]

Ok, Just to sort of clarify and sum up:
Definitions (From Webster's Medical Dictionary):

Cachexia: A condition of malnutrition and wasting occurring in chronic
illness in the later stages;
        physical ill health with loss of weight and emaciation.
Catabolism: The breaking down phase of metabolism in which complex
substances are 
        converted to simpler substances.
Anabolism :Opposed to catabolism in the metabolic process by which the body
substance is built up.
Emaciation: wasting of flesh; the state of growing extremely thin.

Susan, I'm afraid your use of cachexia is inappropriate-emaciation or
excessively 
thin would be better. Your condition score of less than 4 horses hopefully 
were not clinically ill-just very thin with minimal body fat. 

Ti: all exercising horses are catabolic!

When we are talking about feeding these critters, it is important to not lose
sight of the fact that calories are calories. If a horse consumes less
calories
than it is burning, it will catabolize (see the definition above) it's body
fat,
protein or glycogen stores to meet the energy requirements. In a
non-exercising,
healthy horse, body fat is the store of choice, with muscle protein and
glycogen kicking in only
if the deficit is extreme, if fat breakdown is somehow inhibited (high
glucose/insulin),
or in certain disease states. In the exercising horse working aerobically
both glucose 
(carbohydrate) and fats are used. The fats come from circulating fatty
acids from
the absorption in the gut offats and from body fat breakdown, be it from
fat stores or triglycerides
stored in the muscle. Volatile fatty acids, absorbed from the hind gut
fermentation
of fiber and any starches that bypassed the small intestine, can also be
used but are 
funneled through the same metabolic pathways as glucose, not fat.

If the horse consumes more calories than it is burning, it will store these
excess calories
as fat. There is a limit (though the exact limit has not been established)
to how much
glycogen and triglycerides can be stored in the muscle-all those carbos ti
wants 
to feed don't get converted strictly to glycogen, nor does all the fat
loading fat
 go to intramuscular triglycerides. The bulk of the excess calories goes to
fat!

Susan's excellent field survey of the Tevis horses brought to the fore that
rider weight, within reason, did not, in and of itself, influence the 
horse's ability to complete the ride. It was a factor. BUT the most
significant
correlation between horses that completed versus those that were pulled for
metabolic fatigue
was the condition score of the horse, regardless of rider weight, horse
weight,
phase of the moon. The Henneke conditioning scoring system has been
validated to 
correlate closely with the amount of body fat a horse has-says nothing
about catabolism,
anabolism, glycogen stores, or fitness. What is does tell us is the
relative amount of stored energy the
horse has under it's skin-not necessarily what it has in it's gut or
circulation.
Susan's study showed conclusively that, under the rigorous Tevis condition,
horses
that do not have adequate body fat stores to draw upon have a higher risk
of metabolic
fatigue and failure. If these skinny, low fat horses were carbo charged
every hour or so,
giving them the glucose to run on (need not worry about inhibiting fat
mobilization here-
they don't have any to spare!) they probably could do ok. But carbo
charging is not
yet an exact science, and if done wrong, can result in hypoglycemia (low
blood glucose)
or worse. Our horses are working predominately in the aerobic realm-burning
both glucose
and fat. Susan's study emphasized the importance of having those fat
stores, regardless
of speed, feeding regimen or training. And I do not mean jiggling pones
of fat (I believe condition scores of over 7 (considered moderately obese)
did poorly too, no Susan?), just a nice smooth look-no ribs or hip bones
jutting out. 

On a personnal experience note:
Fling had her best recoveries and performance ever this year, when she was
carrying a good 50
to 75 lbs more weight than last year. I had to press her flank a little to
feel a rib, her loin was flat,
her neck blended smoothly into her shoulders and her withers had a nice
padding around them-not round,
but smooth.

Ti's latest "proof" from the human literature concluded with this:
>Based on this review, a baseline diet comprising 20% protein, 30% CHO and
30% fat, with the remaining 
>20% of the calories distributed between CHO and fat based on the intensity 
>and duration of the sport, is recommended for discussion and future research.

Who is going to feed their horse 20% protein? The "low" fat diet in this
study was 10-15%,
which is considered high fat in equine rations! Again, horses don't have
gallbladders,
are not adapted over evolutionary time to a carnivorous or even omnivorous
diet as are humans.
Ounces of weight count in human and horse races where maximum speed is
being sought. Ti's
greyhounds with no excess fat have to rely on their carbocharges and
hopefully are fast enough to
get across the finish before they run out of fuel. But a well conditioned
"fatter" horse, 
even carrying a heavier rider, can do just as well, especially in
technically difficult 
rides like the Tevis-Susan's data show this to be true. NONE of this is all
or none-thin
horses have top tenned-even with heavy weight riders, well conditioned
horses with 
light riders have crashed. Read Susan's articles in the AERC news, work
with your horse,
pay attention to it's weight and attitude and enjoy your rides, whatever
your goal maybe-to finish
or to win!

nuff said.

Sarah and the pleasantly plump Fling