Navicular Bone : The deep flexor tendon which passes down the back of….

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Overseas surveys have shown that up to 20% of young horses less than 3 years of age have evidence of spinal cord nerve and brain stem degeneration.

It has not been reported in Australia.

A deficiency of vitamin E, confinement to dirt yards with no access to pasture, diets of processed or pelleted feeds and ingestion of wood preservatives are thought to be the possible causes.

Early cases respond to a diet of green pasture supplemented with vitamin E at 50-100iu/kg body weight. Extruded Feeds The process of extrusion of a finely ground, wet feed mix through a high pressure dry of steam heated screw chamber.

The process cooks (gelatinises) the starch in grains and meals by heating to 135°C for less than one second.

Expansion of the cooked starch allows more efficient digestion by enzymes in the small intestine improving digestibility of starch to 85-90%.

Extrusion reduces the overload of excess starch into the large intestine and fermentation to Dlactic acid.

Extruded feeds are often regarded as ‘cool’ feeds. (See Glossary term).

However the extrusion process, if not carefully controlled, can damage proteins, fats and vitamins in the cooked feed. (Refer to Chapter 2, Fig. 2.3, page XX).

The large intestine contains bacterial, protozoa and fungal “flora”, which total 10 times the number of cells in a horse’s body.

The numbers of flora are influenced by the amount of fibre in a horse’s diet, with highest numbers in grass and roughage fed horses.

The flora digest fibre, proteins and starches, release energy, warmth and minerals from the feed and provide B-group vitamins. Fermentation Flora Forage Generally described as fresh plant material (dry matter plus water) consumed by a grazing animal.

Forage may be derived from pasture (usually a mixture of plant species, which may be native, naturalised or sown (improved)) or from a forage crop (a single species sown specifically to provide forage during periods of slow pasture growth).

For example, oats and barley are commonly sown as winter forages while pearl millet, eg the Feedmill variety, is sown as a summer forage crop.

Forage crops are annuals and have to be sown each year.

Their high yields of quality dry matter for grazing or hay justify their costs of production.

This is a term synonymous with laminitis.

Laminitis or damage to the laminae (See Glossary term) is the initial change that occurs within the hoof.

Founder is the progression of laminitis resulting in tearing of the laminae, with structural changes as the suspension and support of the pedal bone is reduced within the hoof.

The front hooves are normally more severely affected because they bear a greater weight load as a horse stands and moves around.

The deep flexor tendon, which passes down the back of the pastern over the navicular bone in the heel to attach under the pedal bone, exerts a downward rotational force on the pedal bone as it supports standing weight.

This rotational pull on the devitalised pedal laminae causes them to detach around the toe and the pedal bone rotates downwards.

A rotation greater than 5% from its normal parallel position to the inside of the hoof wall is termed “founder”, or the horse has “foundered”.

In severe “founder”, the pedal bone can rotate to push the toe rim through the sole, resulting in a long term, crippling disease.

A term used to describe a dry or dampened feed mix of grains, protein meals, oil and other concentrates blended with chaff, used as a feed to supplement a pasture or hay based diet.

The large intestine formed by the caecum and large colon, small colon and rectum. Founder Hard Feed Hindgut 86 Hyperlipaemia A severe metabolic disorder that affects ponies and has also been reported in thoroughbreds and donkeys.

A survey indicated that 5% of ponies on studs in Victoria were likely to develop the condition.

Hyperlipaemia is triggered by a sudden reduction in energy intake during pregnancy, lactation or as a result of periods of cold weather when energy losses exceed feed intake.

Affected ponies are often fat, and sudden starvation such as denial of pasture by flooding, snow covering, bush fires or long distance travel for more than 12 hours or even refusal to eat poor quality unpalatable hay can be the triggers for the onset of this disease.

Fat stores are mobilised and triglyceride levels increase in the blood and accumulate as lipoprotein complexes in the liver.

Loss of appetite, depression and severe liver damage occur over 7-10 days, which can be fatal.

Prompt treatment in the early stages combined with force feeding to reverse the energy deficit can alleviate the condition.

If not promptly treated, the condition is invariably fatal.

Note: It is unwise to purposely withdraw all food to make a pony lose weight.

Small meals, made up of white chaff sweetened with molasses, must be provided at normal times to avoid onset of hyperlipaemia. Ill-thrift A term to describe a horse that does not do well or put on condition, loses condition or is thin and wasting, often despite a good quality diet.

Heavy parasite burdens, poor teeth, organ diseases, sand accumulation in the large intestine and certain nutrient deficiencies can result in poor condition, a rough coat and an undernourished appearance.

Refers to inflammation and swelling of the laminae (or interlocking “leaves” or “zipper-like” formation) that supports the pedal bone within the hoof casing (capsule) and therefore the skeletal and body weight of the horse.

Physical tearing of the laminae can occur in a horse that is galloped on a very hard surface, such as a roadway or compacted wet beach san.

The most common cause is due to alteration to the blood flow within the hoof.

This occurs as a result of toxins released when large numbers of hindgut digestive flora die in the presence of hindgut acidosis (see Acidosis (hindgut)).

It is also related to toxic shock arising from infection, stress or gut surgery.

It is estimated that up to 80% of laminitis cases are caused by starch and soluble sugar overload from high grain or lush pasture intake.

Circulating toxins in the blood and the effect of reduced blood flow and lower oxygenation in shock are thought to cause damage to the soft laminae and bonding (basement) membranes of the laminae, resulting in fluid accumulation, internal pressure and weakened bonding.

Laminitis is a very painful condition, usually located around the toe area as the swelling is enclosed within the hoof shell, making the horse extremely lame.

Immediate therapy needs to be targeted at the underlying cause and minimisation of the progressive damage to the internal hoof structure. (See also Founder – glossary term).

A term used to describe the result of selective grazing of pasture by horses.

The “lawns” refer to the short, close cropped areas of pasture that are selectively and heavily grazed by horses.

In comparison, the less grazed areas or “roughs” contain longer, less palatable pasture, weeds and manure heaps.

After a period of grazing, up to 48% of a pasture will be utilised as the preferred grazing area to form “lawns” leaving 52% to develop as “roughs”, spoilt areas and bare patches.

Horses tend to pass their droppings in the “roughs” or less grazed areas, increasing the build up of internal parasite eggs and larvae.

Over time, most palatable plants are eaten out of the lawn area, allowing weeds to infest the pasture.

An insoluble, non-fermentable structural fibre compound of a plant (not a carbohydrate) that is not digested and passes out in the droppings.

As a plant matures and the content of lignin increases, its fibre becomes less digestible.

A mineral, including calcium, phosphorus, magnesium, sodium, potassium and chloride that is required in amounts of more than one gram daily per 100kg bodyweight by a horse.

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