There is an old maxim: "You are what you eat!" Basically this is
true, except for one small detail - it's the wrong way round!
What you are, or in the case of the Performance Horse, what you
do dictates what you should eat. Traditionally it has been accepted
that the more intense the exercise you put your horse through, the
more "fast release" energy you should be feeding. But fast release
is not necessarily the same as readily accessible and,
biochemically, there are storage "areas" for energy irrespective of
whether you are feeding fast or slow release energy sources. Slow-
and fast- release are not terms that are applicable to a
performance horse.
What needs to be looked at is how the endurance horse performs
and how we can supply the correct energy profile to optimise that
performance. And not only energy. Do we need specific nutrient
requirements for the activity of the endurance horse?
A good endurance performer is a product of a number of different
parts. Conformation, genetics and training are all involved.
Conformation is not necessarily the same as genetics. Studies have
shown that the shape of a horse is more nurture than nature but the
basic frame - the skeleton - is genetic. What hangs on the
skeleton, the muscles can also be influenced by genes; not the
conformation or the number of muscle fibres, but the type of the
individual fibre.
Muscle fibres are the strands of two forms, actin and myosin
that in the presence of specific energy "transmitters" - ATP -
cause the one to slide over the other, drawing the ends together.
Multiply this thousands of times, with strands grouped into bundles
then we have contraction. The number of fibres are species specific
so a Carthorse will have the same number as a Shetland. However
within these fibres there are a number of types, typified by the
blood supply and the number of mitochondria (the cellular energy
generators). Type I, Slow Twitch, and Type II, Rapid Twitch
indicates the effect. Type I is rich in mitochondria and blood and
supports full aerobic activity. As the types change through IIa,
IIx and IIb there is a reduction in mitochondria and an increase in
anaerobic activity. Alongside this is a change in contractions from
slow and moderate (Type I) through to rapid and intense (Type
IIb).
Thoroughbreds have a higher proportion of Types IIx and IIb than
other breeds, and this explains why they make good racehorses.
Rapid, intense anaerobic contractions mean power and speed but,
because anaerobis is not sustainable, only for a short period.
However part Thoroughbred can "donate" extra power, which is why
Warmblood/Thoroughbred crosses can be such good all round athletes.
The endurance horse needs the sustainability of muscle power, as
well as the short, intense bursts.
What you do dictates what you eat. Sustainable power is aerobic, intense power is anaerobic.
If the endurance horse has the correct credentials, training is
paramount to achieve results. The purpose of training, in its
simplest form, is to develop the muscles that are going to be
needed to compete. Obviously all the skeletal muscles will be
involved, as well as most other muscle (heart, circulatory etc. -
sustainability also depends on the ability for oxygen to get to the
muscles!) but the important thing is that the different types of
fibre will be differently affected. What we are trying to achieve
is power and sustainability of that power. As such, for an
endurance horse Type IIa muscle development will predominate,
although Type IIx will be advantageous if bursts of speed, or a
short increase of power is required.
So why do we need to know about this? Training will give the
results we require so that should be that. I refer back to the
beginning of this article. What you do dictates what you eat.
Sustainable power is aerobic, intense power is anaerobic.
When a glucose molecule is metabolised, the first phase can lead
down the pathway to pyruvate, or lactate. Production of lactate
requires no oxygen (anaerobis) but the build up of lactate
interferes with subsequent muscle contractions. In the short term
it gives a rapid generation of ATP for muscle contraction, but it
is the pathway via pyruvate down through the TCA cycle that gives a
sustained release of ATP. This pathway needs plenty of oxygen
(aerobis) and is sustainable over long periods of time (until the
nerve impulses to the muscles become saturated and the muscle
tires).
The key point to this is that although glucose (generally
derived from starch) is needed for the first part of glycolysis
(producing pyruvate or lactate) other nutrients (VFAs - hindgut
fermentation products - amino acids, fats etc.) can join the second
part of glycolysis to provide energy. That is, for intense short
power, starch is required but for more moderate, sustainable power,
protein, fibre and fat can be utilised. Theoretically all muscle
types can be powered by glucose (and therefore starch) as glucose
can fuel both aerobis and anaerobis, but physiological factors
influence the type of fuel available for muscles.
For a normal, healthy horse the amount of starch that can be
effectively absorbed from the small intestine is 3.5-4.0g per kg of
body weight. Higher amounts will enter the hindgut and will have
the potential to disrupt the fermentation of fibre. With the
possible exception of racehorses this value (which equates to a
starch level of 20% of the total diet) will be more than sufficient
to power anaerobis. Aerobis will need to rely on the fermentative
VFAs and fat and protein, although protein is an expensive and
relatively inefficient energy provider.
Understanding this enables us to design a better feeding regime.
Feeding moderate levels of a high starch feed with good levels of
highly fermentable fibre - such as Speedi-Beet or Fibre-Beet - will
give a better energy profile than feeding high levels, levels that
could flood the hindgut with starch. It is with this in mind that
BHF introduced the "Ultimate Performance" feed. Optimising highly
digestible starch levels to minimise hindgut levels - all the
glucose goes where it is needed, whilst supplying quality fibre,
fat, protein, vitamins and minerals allows the endurance horse
owner the flexibility to provide the correct energy profile for the
horse to perform. Keeping protein at a reasonable level (the
protein requirement for an exercising horse is not substantially
increased - too high a level can allow fermentative amines in the
hindgut to cause toxic effects when absorbed) will ensure it is not
wasted as an energy source and that VFAs and fats are fully
utilised for aerobis.
With the inclusion of a range of antioxidants, because oxidative
free radicals increase with exercise, plant extracts to maintain
the integrity of tissues such as the gut lining and the airways and
yucca extract to "trap" negative nitrogenous agents in the hindgut
Ultimate Performance is ideal for endurance horses. When fed with
Speedi-Beet or Fibre-Beet as a wet feed, re-hydration is
facilitated.
It is through understanding the physiology of the horse at a
micro-level, as well as a whole that enables BHF to design a feed
fit for purpose. BHF believes it goes a little bit further to
produce the ultimate performance feed.