Glucose and performance
RALSTON@AESOP.RUTGERS.EDU
Fri, 28 Nov 1997 11:50:41 -0400 (EDT)
I replied privately to ti but, in the light of
his recent posts, feel I have to once again
remind everyone that the benefits he is claiming for
grain and glycogen loading pertain to Standardbred and
thoroughbred race horses, which perform anaerobically
at maximum speed for less than 3 minutes. Their muscle
metabolism requires the glucose/glycogen stores to be
available. HOWEVER, our endurance race horses are
performing for hours AEROBICALLY-a type of work
in which while glucose/glycogen can be used, the
most efficient energy source (lowest heat generation, highest
calories of energy available for muscle contraction)
are fatty acids-either from moblization of fat stores or
the by-products of fermentation of hay or forage (yes, hay
has a lower calorie per pound as fed, but once those fatty acids
are made and used by the muscles they are efficient). High glucose stimulates
high insulin which inhibits the mobilization and utilization of
FAT while enhancing use of glucose. Great for that final race to the finish
line but not in the best interest of the horse during the hours it takes to
get there! Yes, many horses are fed grain before and during endurance races
without obvious ill effects. There is a lot of leeway here and individual
variation. Unfortunately equine nutrition is not an exact science as yet,
and probably never will be due to the extreme variability of performance
type, effects of weather, terrain and individual variation! My best advice
is to keep it simple, avoid extremes, learn as much as you can about
digestion and metabolism in horses from scientific sources (much as
I like Michael Plumb's Journal, he openly admits it is
not scientific-great for comparing rump rugs but sometimes
a bit inaccurate when discussing biological things like feeding and textbooks
written before 1989 or so can be woefully out of date). Above all
else, if it ain't broke, don't fix it-if your horse is performing well,
bright eyes, shiny coat good weight, don't go trying all sorts of
additives or drastic changes in what you are doing! I highly recommend
Lon Lewis's Feeding and Care of the Horse, 2nd edition, published in 1995
by Williams and Wilkins (A paper back-relatively inexpensive) for those who
want the most up to date scientific info on horse nutrition.
Sarah Ralston, VMD, PhD
Diplomate, American College of Veterinary Nutrition
Associate professor
Cook College, Rutgers University