Handy Hint 1
Aged Horses are Often Slow Eaters
Aged horses often eat slowly because of deteriorating dental health.  This can lead to less efficient grazing and loss of condition.  An aged horse, as a member of a horse group, may not be able to consume a hard feed as quickly as younger horses.  An aged horse often rests when eating, compared with younger horses.  This can result in their allocated portion being ‘stolen’ by younger or more aggressive horses.  If possible, it is best to feed an aged horse(s) separately from the main group - fence off a corner of a paddock with an electric fence to provide a separate grazing and hand feed area for an older horse.  Alternatively, bring the older horse into a stable to eat as it wishes to overnight in a warm, quieter environment and rest on a comfortable bed.

Handy Hint 2
Regularly Check Aged Grey Horses for Melanomas
Melanomas are formed by the proliferation of melanocytes, the pigmented cells in the skin.  Grey horses appear to carry a genetic prevalence to developing melanomas as they age beyond 6 years of age, with an incidence of up to 80% in grey horses over 16 years of age, with up to 34% of melanomas being malignant in aged grey horses.  Check your aged grey or black coloured horse at monthly intervals for developing single melanoma lumps under the tail base, the sheath, around the anus, mouth and under the ears as these are the first sites where melanomas usually start to become obvious or can be felt in the skin layer.  In time, as a horse ages, melanomas often spread to join together (coalesce) to form one large growth.  In the long term 34% of melanomas can metastasize to the lymph nodes, the lungs, liver, spleen, muscles and the parotid salivary glands at the base of the ears. Consult your vet for specific advice on surgical removal or control by chemotherapy or the new gene DNA plasmid compounds.

Handy Hint 3
Increase Hard Food Prior to Winter
The increased loss of body heat as the overnight temperature drops in autumn leading into winter, saps energy and can quickly result in weight loss in an aged horse.  A few days of cold wet weather without an adequate rug, or a covered shelter, increases heat loss by up to 20 times, causing a rapid weight loss which may not be able to be regained in the short term by an elderly horse.  It is best to increase the amount of good quality hay and easily masticated and digested hard food (chaff, pellets or cooked, senior food), a month or so before the cold, wintery weather sets in to avoid the risk of a sudden weight loss in an aged horse over-wintering at grass.

Did You Know That...
Water is the largest weight of ‘food’ ingested each day by a horse.  A resting 500 kg horse on dry feed or a hay based ration (contains 10-15% moisture) consuming 8-10 kg of feed per day requires about 25 litres (25 kg) of water to drink.  A grazing horse needs to consume 35 kg of green grass (80% moisture content) to maintain itself, which provides around 8 kg dry matter and 27 litres of water. Horses grazing on succulent pasture, with dew on the grass in the mornings, often drink little additional water, unless it is hot or they sweat during exercise.  A 500 kg horse’s body contains about 320 litres of water, over 200 litres within the cells and 110 litres as blood cells and fluid, digestive and extra cellular fluids. The primary need for adequate water is for thermoregulation as horse’s sweat to cool. However, water is also essential for digestion, by-product and toxin absorption and removal, joint lubrication, fluid cushioning of the brain and spinal cord and the maintenance of the skin. The skin is the largest ‘organ’ in a horse’s body, accounting for 3.5 square metres of surface area and the skin of a 500 kg horse weighs approximately 30 kg. During a gallop, approximately 3 litres per minute of oxygen gas leaks or escapes from the massive network of surface blood vessels used to transfer heat and sweat, within the skin.

Parasite Control
Aged horses and ponies are at high risk of harbouring internal parasite burdens due to a lowered natural immune function and slow response to immune challenge. Medications such as non-steroidal anti-inflammatory agents (NSAIDs), most commonly synthetic cortisones and ‘bute’ for allergies, colic or chronic lameness, further reduce the immune function in elderly horses, increasing the risk of parasite colonisation and poor response to booster vaccinations. Natural immunity against Large Roundworms (Ascarids) naturally builds up in young horses by 12 months of age, but in elderly horses, the immune resistance against this worm reduces. Often in sick and elderly horses, burdens can increase to cause ill-thrift, weight loss and intermittent colic.  Infection is likely when an elderly horse acts as a companion/nanny for weanlings and yearlings which harbour the worm. Small Redworm (Cyathostome) burdens are universal in all horses, with an increasing incidence in aging horses grazing on pastures highly contaminated with Cyathostome infective larval stages in early spring, leading to colic, weight loss and wasting if not recognised early and controlled. A similar pattern applies to Pinworms and even Tapeworms in elderly horses grazing in groups with younger horses.

Not all elderly horses develop high burdens of Cyathostomes and over-worming at set 6-8 week intervals, can reduce any low immune suppression worm burdens and encourage further colonisation. Therefore, in aged horses, regular 6 monthly faecal egg counts are recommended to monitor Large Roundworm and Small Redworm burdens can be used to determine the need to worm an aged horse and to select types of worming combinations to maximise worming efficiency.

Did You Know That...
The white cells in the blood (including eosinophils cells), are produced in the bone marrow and are spread throughout the body and skin to act as sentinels. They release histamine in response to insect bites and stings to trigger a local inflammatory reaction which mobilises other defensive white cells to congregate at the site. Eosinophils have a specific function to recognise and kill parasite larvae as a foreign organism invading the gut wall or remaining, in the case of resting stage Small Redworms, in cysts over-wintering in the hind gut lining.  All horses, but especially elderly horses harbouring Small Redworm ‘resting’ stage larvae in the hindgut wall protected cysts, will have an immune response triggered by an increase in eosinophil cell counts up to 4-8% in the white blood cell differential fraction. Unfortunately, as a horses ages beyond 20 years old or more, the immune response to worm larval invasion is much less active, and elderly horses can build up burdens which can reduce their defence against other diseases as well.
If a horse has a high eosinophil count due to burdens in excess of 500 eggs per gram of droppings with Small Strongyles, eosinophil levels in the blood will take up to 8 weeks to return to below the normal 2% after the horse has been wormed out with an effective product containing Moxidectin® (eg Equest gel ®), or alternatively, a 5 day course of fenbendazole® (Panacur 100® at 10mL per 100kg body weight).

Handy Hint 4
Maintain Strict Grazing and Stable Hygiene for Aged Horses
Elderly horses have lowered immune defence against internal parasites. It is most important to maintain the grazing and yard environment as free of droppings as practicable in order to minimise re-infection with worm eggs (Large Roundworms - especially in a senior horse acting as a ‘nanny’ for a group of weanlings and yearlings) and worm larvae (Small Redworms on heavily contaminated grazing areas shared with other horses, especially during spring and autumn when larval activity is facilitated by warm, damp weather).  Removing the droppings at least once a week from a small paddock and daily from an overnight holding yard, will help to reduce the uptake of worm eggs and larvae shed by most common worm species. Maintaining a high standard of hygiene will help minimise the risk and the harmful effects of worm burdens for an aged horse, which even a relatively light infestation, would not normally cause worm related colic or weight loss in a young horse.

Handy Hint 5
Remove Common Worm Burdens
Immature and adult Large Roundworms and ‘resting stage’ cysts of Small Redworm larvae in the wall of the hind gut, with release in early spring, can cause weight loss, low grade diarrhoea, anaemia and colic discomfort in elderly horses, as well as increased risk of sand colic in aged horses grazing on sandy country. An early spring worming with fenbendazole (100g/litre), liquid wormer such as Panacur 100®, given in the feed or over the tongue at 10mL per 100kg bodyweight for 5 consecutive days (50mL for a 500kg aged horse) will help to remove resting stage Cyathostomes gently without untoward colic reaction in most elderly horses, as well as control Large Roundworms and Pinworms in horses and ponies where possible ’mectin’ wormer resistance is present. This can be repeated in late summer (February) to reduce over-wintered burdens. A worming for Tapeworms and bots can be carried out in mid-May and mid-Sept to mid-October with an effective combination. Consult your vet for more specific advice if faecal egg counts reveal particular species or high ongoing worm burdens.

The Immune Response Diminished by Aging
Stress, poor nutrition and aging, have been shown to all compromise the immune system’s response.  Even healthy elderly horses start to wane in their immune response to vaccination compared with a young horse, or when challenged with worm larvae by a heavily contaminated environment, or by specific viral or bacterial infection.  Many elderly horses are more prone to hoof abscesses and bacterial skin conditions, such as greasy heel and rain scald (mud fever) because their immune response is less specific and immune ‘memory’ to earlier infection is reduced.

Did You Know That...
Immune cells and antibodies are produced within the bone marrow, thymus, spleen and local lymphoid tissue in the gut to maintain immune defence as the system recognises foreign antigens such as microbes, allergens, parasites and even cancerous cells.  The immune system must also recognise old invaders to which it has reacted previously, which is referred to as an ‘amnestic’ or ‘memory’ response.  This also wanes as horses age.  Bodies called ‘Peyers Patches’ provide the lymphoid tissue defence against gut lining invasion by foreign bacteria and viruses.  The immune system defence is dependent on the supply of adequate protein and amino acids from the diet to form antibodies and immune fighting cells.  Antibodies are immune proteins or immunoglobulins generated by response to virus and bacterial invasion as primary targets of the immune defence reaction.  Antibodies recognise and attack specific antigens or foreign cells to hasten their destruction and expulsion by engulfing blood cells.  Many aged horses become stressed by cold weather, chronic disease conditions and even physical stress with low grade pain. Natural cortisone release acts to suppress the immune response.  It is essential to maintain adequate good quality protein, trace-minerals, such as zinc and selenium and Vitamins A and E in the diet to help provide the base for immune response. 

Handy Hint 6
Feed to Maintain Overnight Core Heat
Old horses over-wintering in a paddock may lose excessive heat as the overnight temperature drops below 8oC.  If the animal is located in a poorly sheltered area, the wind chill factor during cold or wet weather can reduce the ambient temperature by at least a further 10oC. Under these extremely cold conditions, it is best to walk the aged horse to a stable and cover the body with a light-weight quilted ‘combo‘ rug and provide a warm bed overnight. It is important to provide an elderly horse with a hard feed as a night feed to help maintain energy replenishment overnight.  Many elderly horses will lose body condition and it will be difficult to replace, even as spring grazing and daytime warmth helps them regain energy stores from higher quality grass and legumes in spring pasture.  Although many owners feed a commercially prepared feed and chaff if the horse’s teeth are in poor condition, during very cold conditions and wet weather, an additional source of slow release energy can be provided by adding an extra 1 litre of steam-rolled barley per 250 kg body weight, especially if an elderly horse loses weight over a short period.  This extra feed can be provided again in an early morning breakfast to top up energy and provide a sustained energy release during slower digestion of barley starch.  A ‘ slurp’ of garlic flavoured oil, such as 15ml per 100kg bwt of Kohnke’s Own® Energy Gold™, mixed into the feed will often help entice the aged horse to eat, as well as help maintain the coat under wet conditions.

Handy Hint 7
Assist Old Horses to become more Mobile
Many elderly horses have difficulty in raising themselves to stand up after lying down to rest in the paddock, shelter or stable overnight.  In some cases, they may lack energy and muscle strength due to energy drain overnight under cold conditions.  Simply, provide a quilted, ‘combo’ rug to reduce heat waste overnight. This will help keep the joints and body core warm and conserve energy for an early morning start to the day. Feeding extra energy, as recommended in Handy Hint #6, will help provide an energy boost in a night feed to meet demands when getting up and moving around during the early morning.  If an elderly horse has stiff limbs due to an arthritic joint or lower back pain, providing a maintenance dose of ‘bute’ to relieve low grade pain may be recommended by your veterinarian.  However, it is important to avoid prolonged doses of ‘bute’ for more than 5-7 days, as it may result in a high risk of gastric and duodenal ulcers. Monitor the benefit and reduce the dose to a maintenance level to maintain the horse in a comfortable, mobile condition. In aged horses with reduced joint flexion and ‘creaky‘ joints, a daily supplement of a joint active preparation, such as Kohnke’s Own® Nutricart®, may be beneficial to assist joint function and health and enable the animal to walk and graze without discomfort.  Consult your vet for advice.

Handy Hint 8
Supplement Immune Active Nutrients for Sick or Debilitated Aged Horses
A diet containing 14-15% good quality protein, based on soyabean, lupin or canola meal proteins, in contrast to copra meal which is a lesser quality protein meal, will help provide the range of amino acids to maintain the immune response. A daily supplement, such as Kohnke’s Own® Cell-Provide®, will help to make up shortfalls of a large range of important micro-nutrients which are often low in pasture and hay based diets of paddock fed elderly horses. However, if an elderly horse develops an infection, besides a course of treatment with appropriate anti-microbial drugs under the supervision of a veterinarian, an immune support supplement, such as Kohnke’s Own® Activ-8™, given as a dose morning and night for 10-14 days, and then daily for another 2 weeks, may help support the immune system with nutrient co-factors as it recovers.

Cushing’s Disease
Equine Cushing’s Disease, also known medically as Pituitary pars Intermedia dysfunction (PPID), has increased in incidence world-wide in horses and ponies over the past 2 decades.  A recent survey suggests that it may affect up to 20% or more of horses and ponies over 15 years of age. Cushing’s Disease appears to have a higher incidence in many pony breeds compared with horse breeds, especially grey ponies, and it is most commonly seen in aged ponies over 15 years.
PPID Cushing’s Disease is an endocrine (hormone) disorder of the pituitary gland, a small gland at the base of the brain, which secretes many hormone precursor compounds to trigger the adrenal glands, ovaries, urine excretion in the kidneys and the function of many other organs.  In horses or ponies affected by PPID, the pituitary gland enlarges, or can become cancerous, to rapidly increase in size (referred to as hyperplasia), with a corresponding increase in the secretion of certain hormones. 
It is important to note that ongoing Equine Metabolic Syndrome (EMS) can also result in Cushing’s Disease and the signs in affected horses and ponies are similar to the signs seen in horses or ponies with the PPID form of Cushing’s Disease.  The EMS type of Cushing’s Disease can sometimes be distinguished from the PPID type when a horse or pony does not respond to medication with the drug pergolide, which acts to reduce over-production of ACTH by the pituitary gland. Occasionally, both the EMS and PPID types of Cushing’s Disease can be present in the same animal.
Over recent years, the increasing incidence of the early symptoms or full clinical signs of Cushing’s Disease developing over a 6-24 month period, has resulted in more sophisticated blood tests as a screening tool to check for, or confirm Cushing’s Disease in horses and ponies with typical clinical symptoms and appearance, or ongoing chronic laminitis not related to excessive carbohydrate intake in the diet.  Normal routine blood profiles to check blood cell counts and biochemical parameters are of little use in diagnosing Cushing’s Disease, so researchers have developed new, more accurate tests. Consult your vet for advice on the testing available for Cushing’s Disease. More information on managing Cushing’s Disease is outlined in Fact Sheet C3, available from Gary at newsletters@kohnkesown.com or from the website www.kohnkesown.com.

Handy Hint 9
Symptoms of PPID Cushing’s Disease
It is a good idea to regularly check aging horses every 4-6 months for early signs of Cushing’s Disease. It is suggested that if an aging horse exhibits at least 3 or more of the following symptoms, further investigation by taking a specific blood test should be carried out by your vet. The earliest symptoms are often missed, but any of the following signs are early warnings of developing PPID Cushing’s Disease:

• Development of a long hairy, often curly winter coat which is slow to shed or remains long and shaggy, particularly on the front of the shoulders, during spring and summer.
• Many horses start to drink more water and flood their stables at night, saturating the bedding with an increased volume of dilute urine. 
• Muscle loss leading to ‘melting away’ of the top-line.
• A distinctive pot-bellied appearance not associated with old age ‘under-belly droop’ or heavy worm burdens.
• Change in body fat reserve accumulation on the lower neck, behind the shoulders and tail butt area, especially soft fat filling the hollows above the eyes.
• Loss of appetite with a lethargic attitude.
• Repeated bouts of laminitis and founder. 

Many horses can also suffer; hair colour loss; reduced ability to sweat; exercise intolerance; loss of fertility in mares and an increased risk of worm burdens and microbial skin infections.

Skin Cancers
Although sarcoids are the most common form of skin cancers found in horses (around 40% of all skin cancers), the highest prevalence of sarcoid skin tumours is in horses 3-6 years of age, often confined to certain bloodlines.  However, squamous cell carcinomas (SSC’s) or malignant skin cancers of the white of eye (sclera),  the eye socket, eye brows, non-pigmented under white nose blazes and the penis of geldings, which account for 12-20% of all skin cancers, are more prevalent in middle aged to elderly horses, especially on the borders of non-pigmented skin patches in the hair coat.
 
Melanomas are by far the most prevalent of all skin cancers in elderly horses, with up to 67% prevalence in aged grey horses, although melanomas on dark pigmented coated horses are more malignant and grow quickly. (Refer to Handy Hint #2.)

Eye Problems
Aged horses have a higher incidence of Squamous Cell Carcinoma lesions around the eyes and on the white sclera of the eyeball.  However, loss of vision acuity due to retinal degeneration is common in certain bloodlines of aging Thoroughbred horses.
Elderly horses that ‘shy’, exhibit fear-like avoidance behaviour at new objects or become more anxious under early morning or evening low light conditions, may have an eyesight problem in one or both eyes.  Common causes include corneal ulceration or scarring of the clear front area of one or both eyeballs, with loss of visual acuity, reduced central or peripheral vision due to corneal scarring, and in aged horses, retinal degeneration.

Many dark coloured aged horses are prone to the development of enlarged corpora nigra bodies which hang down into the pupil opening in the eyes.  These act like ‘scalloped’ blind edges to diffuse sunlight to enable horses to graze under high light midday conditions or survey the horizon when the head is lifted into bright sunlight.  In some elderly horses, the corpora nigra undergo a benign enlargement to partly restrict vision around the edges of the iris or pupil, especially under low light overcast or evening light conditions, or when the head is held more vertical, making the horse lose visual acuity and result in the animal developing an uncharacteristic anxious demeanour.  An examination by a veterinary ophthalmologist is recommended if a horse has distinct avoidance behaviour on one side or lacks confidence to work or move to one side.

Handy Hint 10
Examine the Eye Pupil Reflex Using a Torch
If you suspect that your elderly horse is going blind, a simple check by shining the beam of a small torch into the eye when the horse is in a darkened stable, will help to determine whether light is being refracted by corneal scarring or internal lens damage or retinal degeneration. With corneal scarring the pupil will usually constrict slowly, but with lens damage or retinal degeneration, the pupil will often only constrict partially as compared to the other eye.  Also check for enlarged ‘black bodies’ hanging down in the pupillary opening (corpora nigra).  Consult your vet as a detailed ophthalmic examination may be required.

Handy Hint 11
Check for Skin Growths in Aged Horses
If you have an elderly horse, it is good practice to check the predilection sites for common skin cancers around the eyes and penis (Squamous Cell Carcinomas (SCCS) on non-pigmented skin), the sheath, check for raised black lumps under the tail, around the muzzle and below the ear, which are common sites for early melanomas.  Older grey Arabians have a genetically influenced higher incidence of melanomas, with Clydesdale, Appaloosas, Paints and Pintos being more prone to SCC’s. Consult your vet for advice if you notice any growths or lumps appearing in these predilection sites in an aged horse.

Organ Diseases
Although the spleen, liver, kidneys and other small capillary network vessel supplied organs are prone to metastatic tumour spread from CCS and malignant melanoma, the most common organ disease in aged horses is liver fibrosis. Kidney disease, usually as a result of neoplasia or chronic ingestion of pasture contaminated with lead as a fall-out near lead smelters, is rare.

Occasionally an aged horse will develop ongoing liver cell damage due to the ingestion of grazing plants containing pyrrolizadine alkaloids, most commonly Paterson’s Curse (Salvation Jane) (Echium plantagineum), and to a lesser extent, fireweed (Senecio madagascariensis) and heliotropes (Heliotropium spp), as these plants are less palatable to horses. They may be grazed during drought where there is little other feed available. Heavy winter and spring growth with heavy infestations of Paterson’s Curse (Salvation Jane) in the flat succulent rosette stage often dominate the pasture, with hungry or cold horses seeking out the young plants, which can result in liver damage within 5-6 week of ingesting these plants in both young and elderly horses.

Aged horses with liver disease require specialised dietary management in an attempt to maintain adequate body condition and quality of life. Dietary management includes feeding a low fat diet, preferably less than 5% fat, such as good quality roughage, including soaked grass hay and beet fibre.  Lucerne hay must be avoided so as to reduce protein intake to less than 12% crude protein. Millrun based pellets are suitable, but should be offered in 3-4 small feeds per day to avoid large soluble carbohydrate meals which can overload the remaining functional liver tissue. It is unwise to feed commercial feeds formulated for aged or senior horses as they often contain higher amounts of starches, protein and fat. If a horse is not consuming the bland feed, then small amounts of molasses, apple sauce or blended apples and carrots mixed into the feed may help tempt the horse to eat. Unfortunately, liver damage is progressive and in the long term, support therapy may assist in maintaining a reasonable quality of life for a horse with chronic liver cirrhosis, until the liver fails completely due to the irreversible damage. Consult your vet for advice.

Kidney Disease - Contrary to popular opinion, kidney disease is not common in horses and there is no increased incidence in aged horses. The most common cause of reduced renal function is medication with high doses of aminoglycoside and tetracycline antibiotics for diarrhoea or septicaemia, especially if the horse is dehydrated during the period of medication. Extended courses of non-steroidal anti-inflammatories, such as phenylbutazone, given to an aged horse to improve comfort and mobility when affected by a skeletal or joint injury, may also have a damaging effect on renal function. Studies have indicated that up to 75% of the renal nephrons have to be non-functional before the signs of renal disease become apparent.

Handy Hint 12
Nutritional Support to Assist Liver Recovery
It is helpful to provide supportive nutrition including Vitamin B group supplements, especially choline chloride which provides methyl donors that can help liver detoxification. Many of the popular herbal detox supplements have little or no scientific basis or direct benefit. Providing supplementary levels of branched chain amino acids, including leucine, isoleucine and valine, which are not metabolised in the liver after uptake into the blood, may provide a source of these essential amino acids to the body tissues. Small amounts of 20g per 100kg bwt of a supplement, such as in Kohnke’s Own® Muscle XL®, containing human grade whey powder concentrate to provide branched chain amino acids and other essential amino acids, including glutamine, may help to support liver function. Vitamin C powder 2.5g (½ teaspoonful) per 100kg bwt, may also be beneficial as Vitamin C is synthesised in lesser amounts in a liver under toxic stress. Good quality grass, meadow hay or mixed 50:50 lucerne hay dampened, ad-lib at 500g per 100kg bwt is a good dietary base with steam-rolled barley at 300-500g per 100kg bwt for energy, mixed with beet fibre at 100-150g per 100kg bwt for good quality digestible fibre. Avoid supplementing with brewer’s yeast for B group vitamins and do not supplement with polyunsaturated oils for energy. A daily supplement of trace-minerals and vitamins, such as provided by Kohnke’s Own® Cell-Provide® is also recommended to meet metabolic needs as the liver recovers.

Handy Hint 13
Be Aware of High Oxalate Pastures in Aged Horses
Any horse, especially aged horses, where calcium uptake from the small intestine is less efficient, the grazing of predominately tropical grasses, such as in Setaria spp, Green Panic, Buffel, Pangola, Para grass and Signal grass, as well as summer growing Kikuyu grass, can result in large quantities of oxalate chemicals, which can cause a significant reduction in calcium uptake and over a 4-6 week period, may lead to the development of weakened bones with long term osteoporosis and the appearance of ‘Big Head’.  A supplement of calcium, as provided in Kohnke’s Own® Cal-XTRATM, may be necessary.

Further information is available in Fact Sheet #N5 Calcium and Oxalate Pastures by emailing Gary at newsletters@kohnkesown.comor downloading it from www.kohnkesown.com