Advances in veterinary medicine are helping us to keep horses healthier, for longer. Andrea Oakes discovers how we can eke out the active years
On the hoof
A slower metabolism due to ageing can trigger health changes, including deterioration in hoof horn quality. Master farrier Ben Benson AWCF says that modern materials can create protection for thin soles, but the biggest step forward has been a growing understanding of podiatry – the anatomy and function of the foot.
“Knowing more about the mechanics of disease pathology allows us to reverse-engineer the problem,” says Ben, alluding to specialist shoes that can help with issues such as navicular or arthritic coffin joints. “Mobile gait analysis systems, such as the Werkman Black, allow benchmarking of a horse’s foot flight and landing pattern, so that we can identify small changes and make adjustments.”
Pinpointing the cause of colic can be tricky, but vets dealing with an equine OAP are now more likely to suspect a pedunculated lipoma – a large, fatty lump on a lengthy stalk.
“Strangulation of the small intestine by a pedunculated lipoma is more common in older geldings, and in our hospital is the most common cause of surgical colic in older horses,” says Tim, who stresses that these patients can be very stoical and tend to suffer pain in silence. “Surgery is the only effective treatment, but carries higher non-survival and complication rates than many other types of surgical colic.”
Research has shown, however, that the outcomes for geriatrics undergoing other colic surgeries are generally comparable to those in younger horses.
“Long-term survival for horses discharged after colic surgery does not appear to be affected by age,” adds Tim.
The hormonal disorder PPID (pituitary pars intermedia dysfunction, or Cushing’s disease) usually occurs in ageing horses and can cause signs ranging from abnormal hair growth or delayed coat shedding to laminitis, muscle wastage, excessive drinking and urinating, and recurring infections.
Some reassurance may be found, however, in results emerging from a study by the University of Liverpool with Boehringer Ingelheim (producers of a medication used to treat PPID). While owners scored their horses’ quality of life as six out of 10 at the time of diagnosis, this increased to nine out of 10 with appropriate management changes.
“The findings suggest many horses can go on to enjoy a good quality of life, as long as owners put in the time and effort,” says University of Liverpool PhD student Rebecca Tatum, adding that horses medicated with pergolide scored higher than other treatment groups. “Laminitis is a big risk, but this can be reduced by restricting calorie intake.”
“We know thermoregulation, the body’s ability to return to an optimum temperature range, deceases with age,” says equine exercise psychologist Dr David Marlin, who explains that difficulty in coping with extremes of heat and cold may be exacerbated by underlying heart disease, compromised digestive function or respiratory issues. “Older horses also have a reduced maximal oxygen uptake, so may find exercise more challenging in the heat.
“They have to work much harder to control their body temperature in hot weather, so appropriate shade and regular cold hosing will help reduce stress,” he adds.
A greater understanding of core stability is helping many horses stay competitive into old age, according to Rachel Greetham MCSP, ACPAT physiotherapist.
“We know that better abdominal tone and top line will support a horse’s spine and reduce ‘dipping’ of the back with age,” says Rachel. “Once a horse loses muscle, it’s harder to get it back. Riding walk and trot poles, or using facilities such as water treadmills, increases muscle strength and helps maintain range of movement.”
The development of equine ophthalmology – the diagnosis and treatment of eye disorders – offers hope for horses suffering from age-related ocular problems.
“While cataract surgery is still not as successful in horses as it is in humans and small animals, the techniques and equipment used to treat these lens opacities is improving,” says eye specialist James Rushton, of Rowe Referrals. “And although we still cannot cure uveitis, new treatments include cyclosporine implants – with stem cell therapy under investigation.” There’s also promising progress with corneal problems and cancers of the eye.
“Cancer is more common in ageing horses, but in some cases we can save a horse’s eye with the advanced surgical techniques and therapies now available.”
An ageing heart is more prone to complications, but there is some good news.
“We do see certain conditions more often in horses in their teens or above, such as atrial fibrillation (AF) and aortic valve regurgitation,” says equine cardiologist Dr Lesley Young MRCVS. “Once, we would have left the problem alone, or suggested retirement, but we’re now better at performing a risk assessment and have more understanding of the pathology.”
With newer technologies, transvenous electrical cardioversion – which shocks an irregular heartbeat into a normal rhythm – is more suitable for AF cases of a longer or unknown duration than the traditional medication quinidine.
“We’ve also made progress with ‘wearable tech’ – putting monitors on horses for ECG recordings at home,” says Lesley. “With portable technology, we’re able to do a hospital-quality job at the yard.”
Arteries under pressure
Older horses are more susceptible to aortic rupture, where the aorta (the main artery carrying blood from the heart) or another smaller artery spontaneously bursts. Research by Lisse Vera and Professor Gunther van Loon, from the Equine Cardioteam Ghent University, is seeking to establish the effect of ageing on the equine arterial wall.
“Older pregnant mares can suffer a uterine rupture, while certain medications – notably those administered for some colic cases – can increase a horse’s blood pressure and risk of a fatal bleed,” says Gunther.
“We know human arteries become stiffer with age, but we wondered whether this was the case with horses. And could this be measured?”
The arteries of younger horses were seen to behave differently when put under pressure in vitro (outside the body) and examined with ultrasound.
“The goal is to develop tools to use in individual horses to assess a stiffer artery value, so that those at high risk during pregnancy, while at exercise or on certain medications can be identified.”
Lumps and bumps
Melanomas are thought to affect up to 80% of grey horses aged 15 and above.
“Since horses are living longer, we suggest treating melanomas in the early stages,” says Dr Tim Mair FRCVS, of Bell Equine, who explains that these mostly benign bumps, typically under the tail and on the genitals, can become malignant. “Once they spread, there is no effective treatment,” he says, adding that vaccine trials have produced variable results. “Surgical removal is easiest when these skin tumours are small.”
Ref Horse & Hound; 27 August 2020