The phenomenon of a veteran horse is a fairly new concept.
Working and military animals had a useful, but relatively short,
life and even if retired were not expected to live beyond 15 to 20
years. The increase of the leisure animal in post warBritain, and
across the world, has given rise to an increase in scientific
knowledge of the horse and its physiological and psychological
needs, its health and its nutritional requirements. The result is
both a wish, on the part of the owners, and a need, on behalf of
the equine professionals, to prolong and maintain the quality of
life. Having virtually doubled the life expectancy of the average
horse through changes in lifestyle and through improved nutrition,
over a relatively short time, we need to understand the changes in
the body's function in order to correctly feed for a "new phase" in
the horse's life.
Scientific research has taken off in this field but, due to the
newness of the concept, topics can be sporadic and some areas have
generated more in depth data than others. Even so it is a massive
topic and needs to be reviewed in sections.
This article is mainly concerned with the physical "structure"
of the horse - teeth, bones, cartilage and hooves - the hard
tissues. These organs tend to be regarded as inert, certainly the
teeth and bones, and it is felt there is nothing much we can do as
they get worn down.
However even bones are a dynamic metabolic system that not only
provide physical structure but also have influence over mineral
homeostasis (maintaining the correct levels of circulating minerals
and trace elements), growth factors, maintaining the acid-base
balance in the blood, generating blood cells, detoxification of
heavy metals and fat storage (with associated influence on
immunomodulation).
The Importance of Teeth.
A fairly obvious statement to write about you would think, and
to a greater extent it is. Obviously the prime function of a tooth
is to breakdown food particles. But what does this achieve? It is
not simply a matter of destruction.
When chewed forage will be pulped; the compression will disrupt
some cells that will discharge nutrients into the cud. At the same
time chewing will force water and enzymes into the mix - water
helps to open up the cud to ensuing enzyme (small intestine
digestion) action and salivary enzymes initiate the process.
At the same time the action of chewing wears down the teeth - in
two ways. Firstly the enamel is ground away, needing to be
replaced, and secondly the pressure of grinding acts on the
osteoclasts on the jaw bone causing loss of bone.
In any metabolic or physiological system there is no such thing
as stasis, and teeth are also dynamic structures that are
constantly developing. In the young animal this gives rise to tooth
growth and development, whilst in the adult the action of tooth
attrition (wearing down), is held at bay by the growth of the tooth
and constant laying-down of enamel. As the horse enters his veteran
years, and biochemical/physiological systems slow, attrition gains
the upper hand and loss of integrity of the tooth may occur. It is
not a foregone conclusion that this will happen to a great extent,
but it is equally likely that a horse at any age may have dental
problems and so anything that can be done must be welcomed.
Firstly, however, it should be pointed out that uniform wearing
of teeth probably has no overall effect long term digestibility.
Research has shown that veterans spend a longer time chewing, but
digestibility is not significantly reduced. However it has also
been shown that increasing age accompanies increasing Cheek Teeth
Diastemata and this is associated with colic, due to irregular
chewing patterns.
Many tooth problems are not associated with wear and tear. Gum
diseases and a reduction in blood supply to the pulp are examples
of ancillary change. There are nutritional supports, but these will
be mentioned in later articles.
Ensuring a correct calcium:phosphorus ratio will help support
enamel development, and crystallisation of hydroxyl apatite.
Bearing in mind that much of the natural supply of both calcium and
phosphorus can be bound in fibrous chelates it is important that a
feed supplies readily available supplementation. BHF's Veteran Mix
has carefully calculated calcium:phosphorus ratios that are
augmented by trace element bioplexes that aid absorption and
subsequent anabolic processes.
(A short word on metabolism! Metabolism is a term that describes
biochemical processes within the body. There are two basic types.
Those processes that build or deposit increasingly complex
molecules -anabolism - and those that utilise or break down these
molecules - catabolism. Metabolism is the ever shifting balance
between anabolism and catabolism).
The second "target" for maintaining tooth integrity, in the
context of nutrition of the hard tissue, is the bone that supports
teeth - the jaws. As mentioned physical pressure on the jaws
increases osteoclast activity leading to bone erosion. The tooth
socket may become eroded and loose teeth and loss may follow.
Helping to Maintain Bone.
As mentioned before bone is a complex, dynamic system involved
in a number of key processes. It is however its structural
integrity that causes concern to the owners of elderly horses,
possibly more so in it's interaction with the cartilage caps of the
long bones - the joints. However the dynamics of bone is an area
that selective nutrition can have an impact.
Within the mineral matrix of the bone there are three main cell
types - the osteoblast, the osteocyte and the osteoclast.
Osteoblasts are immature bone cells and secrete the protein
structures that lay down minerals. Osteocytes - mature osteoblasts
- form bone, maintain the matrix and are involved in regulation of
calcium. Osteoclasts are bone re-modellers. They breakdown bone
(resorption), which is "recycled" through the osteocytes.
Again, this is an example of biological systems - anabolism and
catabolism. As the horse grows anabolism outstrips catabolism and
as it ages the shift moves towards catabolism. With maintenance
nutrition - as in the wild - the period where anabolism matches
catabolism tends to relatively long but the increase in catabolism
as the animal gets older can be rapid and decline is a short
affair.
As the horse gets older the resorption of bone will eventually
reach a rate that generation of new material cannot match. We must
try and put off this moment for as long as possible. As with
dentition a correctly formulated mineral package should be provided
so the raw materials to maintain bone are available at their
optimum. But there are other considerations.
Bone formation and resorption is regulated by a number of
hormones, including insulin, growth hormone - anabolic - thyroid
hormone and glucocorticoids - catabolic. In addition prostaglandins
(PG), secreted by the bone cells themselves, have a direct action
both on bone metabolism and also insulin-like growth factors (IGF).
Basically PGE2 causes bone resorption whilst IGF causes bone
deposition.
These factors have their derivatives from fatty acids, such as
arachidonic acid, and these in turn come from the foods the horse
eats.
We have all heard about the heart healthy fatty acids, the omega
3 & 6 fats that are known to have positive effects on the
circulation and smooth muscle action. Those commonly found in
equine foodstuffs can be variants of arachidonic acid and so it is
logical to have them in horse feeds in reasonable amounts. The
ratio between the two, for good effect in the circulatory system,
is well known. However what is less well known is that these fats
also have an effect on bone metabolism. Simplistically omega 3 fats
are involved in the production of IGF whilst omega 6 that of PGE2.
In fact the optimum ratios of these fats for "a healthy heart" are
not particularly good for bone homeostasis.
(Another short note. When it comes to the area of "functional
foods", nutraceuticals, herbs and phytochemicals care needs to be
taken. When using a specific nutrient or biochemical to target a
specific function it must be realised that this nutrient will have
other, possibly less desirable, effects. For example the
antioxidative and anti-inflammatory effects of herbs are well known
and extremely effective but, for example, turmeric can reduce
platelet activity - increasing bleeding times, whilst garlic - at
elevated levels has been associated with Heinz body anaemia.)
Luckily there is another natural fatty acid, previously
overlooked but gaining in scientific acceptance that has been
around but suffered from general bad press due to its origin -
conjugated linoleic acid (CLA).
CLA is a fatty cid that has both cis- and trans- bonds. Although
trans- fatty acids have been shown to be unacceptable the
cis-/trans- combination in one fatty acid is unique and has many
positive effects. Not only does CLA combat the formation of PGE2
(working as an antagonist to omega 6) in the bone it also acts as
an ally of omega 6 at the heart and smooth muscle.
So what is the source of this wonder fat? Whole milk. Research
is showing its benefits in human nutrition and overcoming the bad
press of milk fat (Humans ingest too much fat, and do not burn it
off - whether saturated or unsaturated. Horses ingest less, and
their metabolism is more geared to fat catabolism).
By including whole milk in the Veteran Mix, CLA along with omega
3 can help maintain bone homeostasis, smooth muscle integrity and
also the viability of joints.
Helping to Maintain Joints
Although cartilage is widespread throughout the body it is most
noticeable, when poorly functioning, at the joints between the long
bones. Osteoporosis and arthritis are diseases associated with
malfunction of the joints and are characterised by necrosis of the
cartilage and inflammation.
It is generally accepted that the necrosis and subsequent
inflammation is a result of years of wear and tear (or the anabolic
ability is overtaken by the catabolic activity and mechanical
wear). When damage occurs the synovial fluid fills with
glycosaminoglycan (GAG) that is derived from simpler chemicals such
as glucosamine and chondroitin. People naturally believe that
supplying these materials will improve joint health.
However, although it is accepted that the release of GAG is in
response to cartilage damage, and that glucosamine and chondroitin
can increase GAG release (as long as they can get inside the joints
- a route not directly proven from the gut!) it may be that the
result is ineffectual. In many cases the horse will be able to
produce sufficient GAG itself, and it will only increase production
if damage occurs. So what causes the damage in the first place?
There is not doubt that mechanical wear and tear can and does
damage joints. However the veteran horse is less likely to undergo
hard exercise than its younger self and it can be argued that, as
long as the joints have healed, it is at a lower risk than when
younger. However there are other causes of inflammation and
necrosis, and many of these derive from nutritional imbalances.
One of the most significant attackers of the cartilage is
fermentation end products of nitrogen sources in the hindgut. In
short excess protein, or imbalanced protein, passes into the
hindgut where they are fermented by the microflora. In such cases
nitrates and nitrites are released and absorbed across the gut.
These and other oxidative end products attack the cartilage,
causing necrosis. In such cases GAG release is likely to be
bypassed and supplementation with glucosamine and chondroitin
ineffective. The trick is to stop these end products being absorbed
in the first place.
For many years it has been known that the extract of the yucca
plant can help reduce "barnyard smells". In actuality the saponins
(emulsifying phytochemicals) of yucca absorb a number of short
chain ionic molecules - such as ammonia - into their matrix making
it impossible to be absorbed. Over the past decade it has been
discovered that they also absorb the very chemicals that attack
cartilage - e.g. nitrites, effectively removing them from
absorption. In addition it is now known that saponins can modify
microbial populations, as a type of prebiotic, reducing populations
of protozoa that, in particular, produce nitrites etc. So not only
do saponins absorb the negative chemicals, they are active in
reducing their output. Saponins also reduce the absorption of
oxidants and peroxides (inflammatory agents) such as some forms of
iron. Yucca also contains other flavonoids, resveratrol and
yuccaols, that have a direct anti-inflammatory affect on tissues.
Finally yucca has been shown to inhibit nitric oxide synthetase.
Nitric oxide can be produced in the specialist joint cells,
synoviocytes and chondrocytes, and its free radical action (being a
nitrite) causes cartilage necrosis. Inhibiting the generative
enzyme reduces the free radical and maintains the integrity of the
cartilage.
Yucca has a multifactorial approach to offset cartilage damage.
By removing the physiological causes of necrosis normal cartilage
function can be extended and, if damage occurs through mechanical
action, glucosamine and chondroitin, as a curative agent, can be
employed.
Veteran Mix has yucca extract, as standard that, with CLA helps
maintain and extend the viable integrity of bones and joints,
ensuring a better quality of life for the senior horse.
Helping the Hoof.
This topic is slightly at odds with the preceding subjects. The
structure of the above concern the development from fibrous
proteins that become mineralised (although cartilage is permanently
one step removed), whilst hooves are derived from structural
proteins and are not mineralised.
Hoof material is keratin, a structural protein rich in sulphur
amino acids, and is generated by the soft tissue of the foot and
grows downwards from this point (exactly the same as a finger nail
growing from the quick). Again we have the biological system of
anabolism - in this case the laying down of keratin - versus
catabolism - resorption (minimal as only the "leading edge" of
growth is in direct biochemical contact with other chemicals via a
blood supply) - and mechanical wear.
If we provide a source of good quality protein rich in available
sulphur amino acids (methionine and cystine) together with
nutrients that have a sparing effect on these amino acids, such as
betaine - a chemical richly sourced in Speedi-Beet, and also supply
the minerals and trace elements that contribute to the biochemical
pathways, and enzymes and cofactors involved in hoof production,
then we can extend hoof quality into the later years.
There are other routes to help maintain and extend the function
of the "hard bits". The bloodstream, the lungs providing oxygen,
the gut efficiently absorbing nutrients all play a part. It is no
use providing the right mix if we cannot get them to the areas they
are needed and cannot provide the basic fuel of oxygen.
As mentioned before biochemistry is all about chemical cycles,
and anabolism versus catabolism. But this is for each individual
function and it cannot be taken in isolation. For the whole thing
to work there is a host of complex regulatory mechanisms including
hormones, nervous feedback, biochemical two way reactions, enzyme
mediation and external stimuli.
Nutrition is the science of supplying the correct mix so that
these functions and mechanisms can happen to the optimum and
provide a "quality" to the whole of an animal's life. It is easy
enough to add a little more energy and protein to a senior mix, but
this can be insufficient. By attempting to understand the processes
involved "quality" judgements on nutritional changes that actually
enhance these processes can be made. Positive and negative effects
from the same source can be balanced against need, and the correct
compromise reached.
BHF, with its Veteran Mix, has done just this. Stepping outside
the accepted "more energy, more protein" ethos BHF is introducing
concepts that we believe will make a difference to the quality of
life to the veteran horse.
This article is sub-titled the hard bits. Following articles are
the "soft bits" - cardiovascular system, muscle condition etc. -
and the "messy bits" - what happens in the gut of the senior horse.
Together, as a whole, they will explain the philosophy and science
behind what BHF is providing in their Veteran Mix, why it may be
seen as somewhat different, and where it is similar to other
products. We don't claim to have exclusive knowledge of equine
nutrition, but we do believe we dig a little deeper.