By Roger Dixon, BVM&S CertAVP(ESM) MRCVS
Ashbrook Equine Hospital
The lifespan of the average horse is approximately 20 years. However, this varies tremendously between breeds and individuals. Whereas 20 years may be considered a ‘ripe old age’ for a thoroughbred, many ponies are still competing into their late teens and early twenties and live well into their thirties.
Caring for older horses and ponies can be a challenge. This article will discuss how their day-to-day husbandry requirements change with increasing age, and outline several clinical conditions common in veteran horses and ponies.
Nutrition and Feeding
Horse diets are becoming increasingly based on ‘fat and fibre’ i.e. good quality forage supplemented with ‘slow release’ energy sources such as oil. This approach satisfies their requirement to graze for approximately 16 hours a day and avoids the glucose peaks and troughs which are associated with readily-digestible concentrate feeds.
As horses age, their digestive system becomes less efficient at converting food into energy together with an increase in their nutritional demands, therefore it becomes even more important to ensure that forage is good quality and fed in sufficient quantities. If the pasture is sparse, it is vital to feed hay or haylage in the field. There are many commercially available feeds for veteran horses; your vet will be able to advise you on a suitable one. If a complete feed is not being fed, it is important to feed a multivitamin and mineral supplement.
The choice of feed may depend on other conditions; particularly dental abnormalities which can prevent efficient utilisation of food.
Dental problems are particularly prevalent in older horses. Horses’ teeth erupt continually throughout their lifetime until their mid to late twenties when they begin to loosen or even fall out. It is recommended that horses have their teeth checked by a vet or qualified equine dental technician at least annually.
The signs that your horse may have a painful tooth problem can include:
- ‘quidding’ (dropping food when eating)
- weight loss
- excessive salivation
- holding the head to one side when eating
- taking longer to eat feed
- resentment of the bit or head-shaking
- a bad smell from the mouth or nose
When horses eat grass or hay, the jaw moves in a circular action to grind down the food; this also naturally wears down the opposing teeth at approximately the same rate as they erupt. However, horses which are stabled for long periods of time without ad lib forage, kept on minimal pasture or fed large quantities of hard feed are unable to spend the necessary length of time chewing to wear down the teeth. The upper jaw in horses is wider than the lower jaw; in horses with limited grazing this results in sharp enamel points forming on the outside edge of the top teeth and on the inside edge of the lower teeth. These sharp points rub on the inside of the cheek and the tongue causing pain and ulceration. These enamel points are removed by regular rasping.
With increasing age, gaps often develop between adjacent teeth. These are termed diastemata and can act as a one-way valve; food is forced into the gap during chewing but may not be able to escape. The build up of food material leads to necrosis of the gingiva (death of the soft tissue around the tooth), subsequent infection and further recession of the gingiva. The periodontal ligament (which holds the tooth in place) may be weakened and eventually the tooth may loosen.
It is only possible to diagnose and fully assess diastemata with the aid of a gag, headtorch and dental mirror or endoscope. Affected horses may have severe dental pain and therefore sedation is often necessary to perform a thorough examination. Diastemata are initially treated by removal of the food material followed by flushing the gap out with an antiseptic solution. Cases usually require flushing on a regular (at least 6 monthly) basis and in many horses this is sufficient to prevent the diastemata from worsening and minimises dental pain. If this is insufficient, some diastemata will be packed with impression material to prevent the ingress of food. More severe cases may require the diastemata to be widened, thus allowing food to escape and preventing a build-up. Dietary management can also be extremely useful; feeding short-length fibre as an alternative to hay, and maintaining the horse on grass pasture for as long as possible can reduce the build-up of food material.
It is very common for older horses to lose teeth, particularly as they advance into their late twenties and early thirties. The tooth opposing the gap from the missing tooth will then have nothing to wear against so can overgrow rapidly. This overgrowth prevents the jaw from moving in a normal, circular motion leaving the horse unable to chew and fully utilise the food. Again, regular checks and rasping will diagnose this condition and keep it under control.
As horses age, their immune system can decline and their ability to fight infections decreases, therefore it is important to maintain a vaccine programme for the older horse even if it is ‘retired to pasture and does not go anywhere’! This is particularly true for tetanus.
Tetanus is caused by the bacterium Clostridium tetani which is found in soil and invades wounds and foot abscesses. It produces a potent toxin which causes nervous signs including a stiff gait and muscle spasms. As the condition progresses, the muscles of the neck and jaw go into spasm, giving the name ‘lockjaw’. Eventually, the horse will be unable to get up and will ultimately die from heart and respiratory failure as the rest of the muscles enter spasm. Even if it is treated early, tetanus is often fatal. Vaccination provides very effective and inexpensive protection from tetanus. This vaccine needs to be done every 2-3 years depending on the vaccine used by your vet.
It is also recommended that veteran horses continue to be vaccinated against equine influenza, even if they are retired. In-contact horses may inadvertently bring the virus onto the yard following competition or training elsewhere, with no apparent signs of disease. Severe disease may then ensue in a geriatric, unvaccinated horse, with catastrophic consequences. Again, vaccination is very effective at reducing the severity of disease.
Equine Cushing’s Disease (PPID)
Equine Cushing’s Disease (or Pituitary Pars Intermedia Dysfunction) is becoming increasingly recognised in middle-aged to older horses.
What Is Cushing’s Disease?
Cushing’s disease results from enlargement of part of the pituitary gland; a small hormone-producing organ which lies at the base of the brain. Excessive amounts of several hormones are produced resulting in a range of clinical effects. A long, curly coat (hirsutism), excessive sweating, fat redistribution around the crest and rump and excessive drinking and urination are some of the more obvious signs. Cushing’s disease can also result in recurrent laminitis and increased susceptibility to parasites and infection.
Cushing’s disease can be detected by measuring a hormone called ACTH via a simple blood sample. Occasionally, we will be very suspicious of Cushing’s despite a negative test result so will undertake further testing to confirm if the horse has Cushing’s.
The aim of treatment is to restore normal hormone levels and therefore minimise the clinical signs. There are three medicines which are used for this; pergolide (‘Prascend’), trilostane and cyproheptadine. It is important to remember that treatment must continue for life and not all cases completely respond to treatment. The cost of ongoing treatment must be considered and balanced against the likely clinical benefits in each individual case. Treated horses should undergo repeat blood tests at appropriate intervals to evaluate the effectiveness of treatment and allow the dosage to be adjusted if required.
Owners can help affected horses and ponies by keeping up with vaccinations, dental care and a good worm control programme. In those horses with long, curly coats, clipping can help them dry off more quickly. It is also important to monitor the horse closely for signs of lamintis.
Many older horses suffer from arthritis, either following a previous joint injury or as the result of general ‘wear and tear’ over many years. Arthritis is characterised by the loss of articular cartilage covering the joint surface and the development of new bone on joint surfaces and margins. It often results in pain, stiffness or swelling around a joint and can vary hugely in severity.
There are many treatments available for arthritis. In older horses, some of the most common include oral anti-inflammatories such as phenylbutazone (‘Bute’) or joint injections with medications such as steroids or hyaluronic acid. Your veterinary surgeon will be able to advise you on the most appropriate treatment for your horse. Long-term administration of oral anti-inflammatories can have adverse effects on liver and kidney function so regular examinations with ensure the horse is given the most appropriate dosages and treatments. Your vet may also recommend intermittent blood tests to detect any effects on the liver, kidneys or protein levels.
The end of the road
Hopefully your horse has had many happy and healthy years of retirement; however, unfortunately the time will come when euthanasia is required. Although this is a very stressful and emotional time, it is worth planning so you can enjoy your horse’s last days rather than worry about the practicalities. Euthanasia is most commonly carried out using a lethal injection although some owners may prefer euthanasia by bullet. It is also worth considering whether you would like your horse cremated and the ashes returned to you for scattering or burying at a later date. In some cases, it is possible to bury your horse at home, but do seek advice regarding this.