Veteran horses: when is the best time to retire? [H&H VIP]

  • When should you wind down the workload with an older performance horse? Lesley Barwise-Munro MRCVS discusses how to read the subtle signs that maybe enough is enough

    This year we’ve seen some of the all-time greats make their final appearances, including eventers Lenamore (pictured) and Headley Britannia, plus dressage stars Mr President and Mistral Hojris.

    Knowing when to call time on a successful career can be tough. How can we judge what’s appropriate for an equine geriatric and whether he should be eased into retirement?

    To try to answer these questions we need some understanding of geriatric physiology, which is becoming increasingly important in equine sports medicine. Around a quarter of horses in the UK are 15 years or older, and a further quarter of these compete in a wide range of activities including dressage, eventing and showjumping.

    In certain disciplines it can take many years of training to reach elite levels. Appropriate management of an older horse is critical to keep him at the top of his game. Owners, trainers and riders must remain vigilant, however, and be prepared to step back if it becomes apparent their horse has done enough at that level and needs to wind down or retire.

    How old is ‘old’?

    The age at which a horse is classified as geriatric is still under debate, but 15-20 years is considered the point at which peak physiological functions begin to decline.

    It would appear that some of the decreased exercise capacity in older horses is as a result of owners prematurely reducing work duration and intensity.

    A decline in cardiovascular capacity occurs with increasing age. Horses around 20 years old have been found to have a permanently decreased maximal heart rate of around 193 beats per minute (bpm) in response to work. This compares to the 220-240 bpm of a young racing thoroughbred.

    This means that when an old horse works at high intensity his heart cannot deliver enough oxygen around his body to meet the demands of exercising muscles. Aged horses therefore start to build up lactic acid in their muscles at much lower speeds compared to young horses, which impairs performance and slows recovery.

    Significant changes, such as a decrease in willingness to work and a more laboured recovery, require veterinary assessment. Early detection and assessment of heart murmurs is important — 20% of over-15-year-olds have been found to have them.

    Age has been identified as a significant risk factor associated with left-sided valvular regurgitation (murmurs), such as aortic and mitral insufficiency (when the mitral valve does not close properly). These conditions can affect performance in ageing equine athletes and their progression should be monitored.

    The warning signs of heart problems can be commonly mistaken as the horse just getting older. Progression of left-sided heart murmurs can be an important reason for reducing a horse’s workload or retiring him from a rider safety point of view.

    Age-related changes

    The respiratory system also undergoes changes with age. Small airway disease, such as recurrent airway obstruction (RAO), exercise-induced pulmonary haemorrhage and hyper-reactive airway disease are common.

    These age-related changes have a negative effect on exercise tolerance. Lifelong exposure to dusts and mould may contribute to this decline in lung function. Good air hygiene is therefore important throughout a horse’s athletic career to prevent airway disease causing early retirement.

    Another potential problem in older horses is a decline in the ability to control core temperature and regulate fluid balance during exercise. During high-intensity work the horse’s rate of heat production can be 40-60 times above resting level. If this excess metabolic heat generated is not dissipated, life-threatening rises in body temperature can develop and affect health and performance at all levels of work.

    Research from the USA studying the effects of age on thermoregulation found that geriatric horses working at the same intensity as young horses reached a body temperature of 40°C in half the time. This problem is linked to the decline in maximum heart rate and cardiac output.

    During exercise the older horse’s cardiovascular system prioritises blood flow to the increased oxygen and energy demands of the muscles. As a consequence, blood flow to the skin and the ability to sweat are reduced. This in turn can lead to overheating.

    Older horses are thought to be constantly slightly dehydrated, which also contributes to the problems of a poor sweating mechanism. Owners, trainers and event organisers should be aware of the need for vigorous cooling of older horses competing in demanding sports, especially at high ambient temperatures and in humid conditions.

    A career rethink

    Unexplained poor performance in horses over 15 should prompt a test for Cushing’s syndrome, which is thought to affect 1 in 5 aged animals.

    Increasing age is also linked with significant changes in metabolism, which can result in obesity. This impairs athletic ability and predisposes a horse to lameness and equine metabolic syndrome (EMS).

    Regular exercise at least 4 days a week is beneficial to older horses to reduce the risk of EMS. Blood testing for insulin resistance can help with more accurate management.

    One effect of age on body composition is a reduction in lean muscle mass and a change of muscle fibre type. The latter also contributes to the lower exercise capacity of aged horses.

    Lameness is probably one of the most common reasons why older horses need to have their work level reduced, be retired or even euthanased. Recent surveys have shown that almost half of the aged population is lame at trot and yet around 40% of this group are still in work at some level.

    Non-traumatic musculoskeletal conditions result from the culmination of many years of athletic activity and relate to joint wear and tear. Joint cartilage becomes more brittle and vulnerable to damage by mechanical loading, leading to osteoarthritis.

    A reduced range of joint motion is a result of joint pain and osteoarthritis and is more common in the knees, fetlocks and hocks. The older horse may appear to become more careless with poles down in showjumping, or even develop a change in front limb jumping action which can have safety implications during cross-country. With correct management, he may continue to perform athletically.

    Recurring or non-responsive lameness that impairs performance and jeopardises welfare requires a review of the horse’s career plan and training methods.

    To conclude, a number of physiological alterations can predispose the older athletic horse to reductions in performance. But with good preventive healthcare, including regular veterinary involvement and specifically tailored training programmes, older horses can continue to perform well into their second decade and beyond.

    Equine athletes enjoy the mental stimulation of working and competing. Where possible, a different career or a more manageable work routine is preferable to complete retirement.

    Horses aged 15-plus: the facts

    A quarter of the UK horse population is 15 years or older. That’s around 300,000 animals:

    • 26% of these still compete
    • 21% are not exercised at all
    • 58% have cataracts (most are older than 30 years on veterinary examination)
    • 20% have a cardiac murmur
    • 14% have lower airway abnormalities
    • 49% are lame at trot (40% of which are still in work)
    • 20% have Cushing’s disease
    • 25% are overweight
    • 95% have some form of dental disease
    • 40% of owners report that the horse has reduced joint flexibility
    • 26% report loss of weight/body condition

    Managing the older competition horse

    Eventer High Learchild gave his best performances aged 16-17, winning at open intermediate and completing Bramham and Blair Castle.

    Craig Anderson, who competed “Sam” for owner Margaret Burns for 8 years, said: “In the latter years he began to change. He took longer to get fit and never seemed to attain his previous peak fitness, often reaching for his second wind on hills and taking longer to recover after cross-country.

    “Warm-up at events meant plenty of long, low stretching to get rid of stiffness, and his canter needed more pace to manage the showjumping.”

    Lameness eventually prompted Sam’s retirement and he was put down at 18 due to a stifle injury.

    “He was not a horse that would take to retirement and the Northumberland winters are long and harsh,” added Craig, who rated Sam as the best he has ridden.

    This veterinary feature was first published in Horse & Hound magazine