At British Horse Feeds we try to understand the whole of the
horse and how it functions. Biochemistry, physiology, immunostasis
and the environment are all factors that determine the nutrients an
animal requires at any stage of its life. Having done that it would
appear a simple matter to provide the correct nutrition!
The fact that we are supplying antioxidants from several
sources, plant extracts and milk to support a number of processes
and have formulated a beneficial profile of energy sources and good
quality protein will not mean much if we cannot get it into the
horse's system.
As ageing brings about changes in bone and teeth (catabolism
overtaking anabolism) and in the soft tissues the changing function
of the gut also needs to be examined.
The gut is basically a tube made of smooth muscle. It is similar
but different from cardiac and striated muscle, but still requires
the same biochemical input as do the others. It may come as a
surprise that the biggest user of protein eaten is not the muscles
of the legs, nor the skin and coat, nor even the heart,but the gut.
Food passing along its length is constantly wearing down the gut
wall and it is constantly being regenerated. As the horse gets
older this rate of regeneration begins to slow. At the same time
the rate of passage - forced by rhythmic contractions - will also
tend to slow and the rate of wear is reduced. However gut wall
contractions are involved in a highly complex set of feedback
mechanisms, hormone and enzymatic release cues all involved in the
optimisation of digestion. For example, stretch receptors in the
stomach have two cues. One release a hormone called leptin that
signals the brain to switch off feeding/hunger cues, whilst the
other signals the small intestine to release enzymes to receive the
stomach contents. Although the horse, being a trickle feeder,
probably does not utilise the first function and is permanently
utilising the second, introducing set meals will enhance them.
Slower gut wall contractions can lead to reduced appetite. A
reduced rate of eating will result in a lower output of saliva, one
of the cues that "set off" a sequence of gut enzyme release.
However a slower gut means that food is retained for longer giving
more time for nutrients to be absorbed. So where are we? Does the
older horse eat less but is hungrier? Does it produce a lower
amount of enzymes but absorb better? Or is there no overall
change?
Recent research has confirmed the enzymes of the intestinal
brush border do decline with age. These include disaccharidases
(those enzymes that breakdown the molecules that amylase from the
pancreas produce when it breaks down complex sugars like starch),
dipeptidases and alkaline phosphatise. As enzymes such as amylase
and protease also decline (overall profiles of enzyme activity do
not appear related to age), the effect is that fewer absorbable
molecules are released from the feed. Even if there is more time
for absorption the overall effect is one of reduced
digestibility.
Feeding the upper gastro-intestinal tract needs to take this
into consideration. By heat processing the raw materials, not only
the cereals but also the protein sources, carbohydrates and
proteins can be made more digestible. Micronization is one of the
best methods; not only can each raw material have a "tailored"
process to make the starch more available, the protein can also
have its digestibility improved by mild denaturation. Enzymes have
an easier access to the chemical bonds and so have more thorough
penetration of the material. Not only broad approaches such as this
are available. The reduction in enzyme activity of the brush
borders are mainly in the jejunum, the area associated with the
release of amylase. Further down the disaccharidases are still at
near full strength. By feeding different disaccharides - simple
sugars (sucrose, glucose and lactose, for example) - the uptake of
sugars, which can be converted to glucose in biochemical pathways,
can be maintained even if the uptake of sugars from starch are
declining.
BHF have replaced a proportion of starch with these
disaccharides to optimise sugar absorption and maintain the energy
contribution of carbohydrates. Likewise with proteins; by providing
protein with high availability potential losses of enzyme activity
can be compensated.
Feeding the hindgut can be a bit more problematical. Nutrients,
whether intact from the feed or partially reduced during their
passage through the upper gut, act as a base for microbial
fermentation. The old adage of you are what you eat is very true
for the microbial population in the horse's hindgut. If high levels
of starch and sugars, or protein, enter the hindgut specific
microbes will grow and colonise possibly pushing out the fibre
digesting bacteria. An older horse may have more difficulty
absorbing these nutrients in the upper gut when on
conventional feed and more starch may hit the hindgut,
disrupting and changing emphasis. By improving the availability of
sugars (as in widening the spectrum of sugars fed, and micronizing
cereals) and improving that of protein, then there will not be an
increase in these nutrients into the hindgut. In such a situation
the microbial population of the hindgut will maintain stasis and
the ability to ferment fibre should be unchanged. Provision of
prebiotics in this case is unnecessary as the nutrients themselves
- especially the fibre profile of Speedi-Beet - will act as
prebiotics. As with the foregut, decreasing intake will mean longer
retention time in the hindgut. This will allow more time for fibre
fermentation and so the overall absorption of nutrients shouldn't
be significantly affected.
British Horse Feeds are investing in the concept of an energy
profile. The current thinking is that fibre is the best thing to
feed a horse and this is true. However two points need to be made.
Firstly there is no natural feeding stuff that can provide fibre
without sugars and starch and secondly the term fibre covers a
bewildering array of types. At the end of the day they are all
carbohydrates; some can be broken down by the horse's enzymes and
some only by the bacteria in the horse's gut. Some can be attacked
by both. Therefore it is important to provide a profile of energy -
different sources and different types - so the whole gut and its
microbial population is playing its role. This includes dietary
oil. Because it is absorbed by a different mechanism to other
nutrients and because its availability can be affected by fibre, a
slight increase for the veteran horse will offset interference from
more prolonged fermentation.
British Horse Feeds have taken time to review the latest
scientific thinking and discoveries on the changes taking place in
the horse as it ages. Biochemistry, physiology, immunology,
nutrition etc. all undergo some changes. It is depressing to think
of it as a decline. It is more of a shift of emphasis from
anabolism to catabolism. It is a continuous process starting with
conception and changes from adulthood are slow.
We don't expect to look into the stall, or out in the field, one
morning and see an animal in sudden decline, and it is a matter of
personal judgement to decide when you feel the feed your horse is
on doesn't seem to be quite doing the trick. That moment may not
come. The horse may cope with his current feed perfectly well, but
most will need an upgrade.
Veteran care is such an upgrade. The ingredients have been
selected to account for these small changes, by widening the
spectrum of nutrients and improving their availability - even down
to minerals and trace elements, supplied as protein chelates - the
most available form. Plant extracts and conjugated linoleic acid
have been incorporated to help maintain bone and joint vitality,
and the whole specification of the feed has been designed to get
the nutrients across the gut wall to where they are needed. And the
simplicity of it is that as the horse gets older, increasing the
amount of Veteran Care will be the best thing to do.
We can't stop ageing and we certainly can't stop its associated
changes. But we can feed to the optimum and, in doing so, help
maintain vitality and quality of life for as long as possible.