The OLDER HORSE
From performance to Retirement by Dr Jennifer Stewart
There is no set age at which horses become ‘old’ as the actual age of a horse does not always match the ageing process of the individual. For disciplines requiring years of training and physical development, peak performance often occurs in the mid to late teens. However, from around 15 years of age, the athletic ability and needs of horses begin to change. The changes associated with ageing are gradual, but by recognising them, we can avoid the pitfalls, smooth the passage and slow the hands of time. Photo of Algebra, ridden by Natalie Blundell until Oct 2014 and then Andrew Hoy (based in the UK) took over the ride, and between them they amassed an impressive list of high performance international competitions. He retired sound from international competition at age 20 and now, at age 24, lives a retired life with owners Julia McLean and John Glenn in NSW. Photo by Julia McLean
S
ome aspects of management of the older equine are fundamental to maintaining any horse, regardless of age. There are common age-associated problems that can be supported by alterations in feeding management. These include reduced mobility due to chronic lameness, inadequate dentition, increased sensitivity to extremes of temperature, apparent malabsorption/maldigestion, recurrent impaction colic, and PPID (also commonly known as equine Cushing’s disease).
Starch/sugar feeds
As horses age, the ability to control glucose and insulin levels declines. Reducing reliance on high sugar/starch feeds and ensuring protein quality and quantity match the horse’s needs, can help Cushings/EMS and older horses with blood and muscle glucose levels. Caution is required when using micronized and extruded feeds. These ‘cooking’ processes are undertaken to increase starch digestion in the small intestine and can increase enzymatic digestion in the small intestine by over 446% - profoundly affecting blood glucose and insulin levels. Sweet feeds often have high molasses levels and these can exacerbate glucose intolerance and should be avoided in horses with Cushings disease.
THE OLDER COMPETITION HORSE
Maintaining ‘condition’ becomes increasingly difficult as horses age. This is particularly relevant for horses that are being ridden or are competing. The ability to sustain work depends on adequate muscle mass. Loss of performance and early onset of fatigue occur when muscle mass is reduced. In addition, loss of muscle tone increases the load placed on tendons, joints and ligaments. These structures become more prone to injury and breakdown, increasing the risk of falls and accidents. The power-to-weight ratio depends on the amount of muscle versus the amount of fat a horse has. Oats, barley and high sugar/starch feeds provide ‘fuel’ for the muscles – but muscle building and repair after work requires protein. Muscle growth - and how well it can respond to training - is dependent on the protein in the feed. This is essential for all horses and becomes increasingly important with age.
EXERCISE? YES!
With few exceptions (and as in most species) whatever gets worse with age gets better with exercise. As our horses age, many of us instinctively reduce the intensity of exercise - but around 21% of horses still compete at 18 years. Between 18 and 20 years of age, horses can experience a reduction in exercise capacity - the rate of decline is influenced by many factors, including genetics and level of activity. However, studies on 20 to 30 year old horses found they were still able to complete strenuous standardised treadmill tests without any special feeds or training. This underscores the fact that, despite reduced exercise tolerance, many old horses can be maintained in good body condition and continue to be ridden and compete well into their 30s. Provided older horses are free from lameness and in good health, they should be able to sustain a moderate conditioning program.
Experienced, well-schooled horses can often maintain fitness with a lower volume of work and this helps reduce stress on the musculoskeletal system. If a horse has been spelled or retired for some time, its worth having a veterinary examination before beginning a training program. Exercise can be beneficial in maintaining joint function and slowing the progress of certain disease, whereas retirement and inactivity can worsen the severity. Although some level of aches and pains is normal with advancing years, there are medications and specialist shoeing techniques that can minimise the impact of age-related degenerative conditions such as navicular disease
Additional nutritional support
for the older horse
Vitamin C low plasma vitamin C may be the result of PPID and/or thyroid dysfunction in old horses and may contribute to the reduction in immune function. Vitamin C supplementation (2g per 100kg body weight) increases response to vaccination. It can also help the immune system during transport stress and supplementation for 5 days before transport can reduce the incidence and severity of shipping fever. However it should not be stopped abruptly – rather tailored back slowly. Vitamin E Supplementing Vitamin E is recommended for aged horses. Vitamin E can improve immune function. Oral joint supplements: Although there have been many reports on the efficacy of these products, there has been a lack of published clinical trials Other nutrients: vitamins A, E, B, B12, C, D and folic acid are important in older horses and the diet should contain recommended levels. Caution is needed as always when using supplements because over supplementation with trace minerals, such as chromium and zinc can be detrimental to immune function. Magnesium: There is also an important interaction of magnesium with the immune and nervous systems, inflammation and insulin. Typical diets often do not meet magnesium requirements – which increase with moderate to intense exercise. And, soaking or steaming hay to reduce starch and sugar intake causes a significant loss of magnesium.
Continued
Magnesium plays an important role in all horses including older horses, for... • immune and nervous system • inflammation • insulin regulation
Magnesium requirements are increased…. • • • • •
in ageing horses during exercise while traveling in breeding mares if hay is soaked or steamed
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The older horse continued...
and arthritis. If you are concerned about the appropriate level of exercise for your horse, seeking veterinary advice can help when developing training programs.
CONSIDERATIONS FOR COMPETITION HORSES
The risk of ‘shipping fever’ or pneumonia is related to the inability of the horse to lower its head for long periods, ammonia fumes from urine and manure, dust in feeds and car exhaust. Monitoring for coughing or nasal discharge and recording body temperature twice dailyduring and after a trip are good preventative strategies. ‘Shipping colic’ is linked to impactions from reduced water intake, grain in the diet, changes in diet or feed quality and low roughage intake. Whatever the feeding regimen, it should remain consistent when travelling and competing.
Feeding before competition:
To reduce the risk of injuries during work, fatigue should be avoided. This is partly achieved by ensuring adequate fitness but also by diet manipulation. Fatigue is correlated with falling blood glucose and muscle glycogen levels and increasing blood lactate (which begins at speeds of 10metres/sec). Feeding strategies should address this. Blood glucose is lowest 90 minutes after feeding high carbohydrate diets and these should be fed no closer than 3 - 4 hours before an event. High oil feeds have been shown to preserve blood glucose and delay the onset of fatigue. This allows horses to maintain work for longer, before fatigue from falling blood glucose begins to affect performance and coordination.
‘Body Heat’
also contributes to fatigue. Reduced cardiovascular function and sweat gland activity also affects the ability to tolerate heat stress. The additive effects of heat from working muscles, the environment and internal metabolism combine to raise the horse’s body temperature and cause sweating. To cool itself by sweating, the horse must divert blood away from the working muscles, and send it to the skin. This reduces muscle blood flow such that oxygen and glucose levels fall and acid levels rise - hastening the onset of fatigue. Sponging with cold water during and after exercise reduces the heat load. The heat produced by working muscles can be reduced by feeding highly digestible, high oil diets and reducing the amount of unusable protein.
RETIRED OLDER HORSES
Generally speaking, most horses over 20 have some type of tumour. Appetite and weight changes may indicate the presence
of a tumour. Thyroid tumours are more common in geldings, while mares are more susceptible to pituitary tumours (Cushings Disease). Although relatively slow-growing and usually benign, both affect the secretion of certain hormones, leading to glucose intolerance and reduced sensitivity to insulin, high blood sugar levels, increased drinking and urination. Other signs of Cushings disease include chronic laminitis, infections, weight loss, compromised immune function and a long hair coat. If these signs are present, a veterinary examination and blood tests are important as with appropriate care and medication the symptoms can often be treated and the horse return to a normal, active lifestyle for many more years. Horses with thyroid dysfunction often respond well to treatment.
Body Weight: Weight loss is not uncommon in elderly horses and can occur secondary to dental abnormalities, kidney and liver disease and Cushings. Risk of weight loss is higher in winter. Body condition scoring (BCS) is useful for monitoring weight loss during cold weather. Weight tapes are more sensitive measures of weight loss. Heart and belly girth measurements are more accurate for monitoring weight changes. Excess weight is associated with complications of lameness, laminitis and insulin resistance. Weight/ condition should be monitored carefully during prolonged bouts of cold weather and the amount of feed adjusted according to Twenty nine year old Flower has continuous turnout with a shelter for protection from the condition loss or gain. weather. Jacqueline Anderson photo
Age and digestive function
No difference has been found between 5-12 and 19-28 year old horses in terms of nutrient needs. The research that showed reduced digestion of fibre, protein and phosphorus was based on studies done over 40 years ago, in the 1980s before wormer pastes were commonly available. Advancing age does not significantly affect digestive efficiency in horses. With adequate worming and dental care, old horses can easily maintain good body condition well into their 20s and even 30s on normal balanced feeds, without the need for special ‘senior’ of ‘geriatric’ feeds.
Body temperature regulation:
Aged horses may require higher energy intakes in cold weather - but old horses that are fat or obese should not necessarily be fed extra just because it’s cold. They will still need protection from extremes of temperature, shelter from direct sun, wind and rain – however, prolonged confinement can worsen stiffness due to arthritis and should be used only if necessary. Continuous turnout with free access to a deep runin shelter is usually the ideal situation. Horses with Cushings should be clipped during hot and humid weather conditions, especially if still being ridden. In very hot weather, sponging with cold water, providing shade and fans will improve comfort and help reduce any heat-related appetite loss.
Worms and teeth:
As horses age, they develop greater immunity to gastrointestinal worms, but if regular worming was not carried out during younger years, there may be scarring and blood vessel damage to the digestive tract. As normal aging processes occur, gut problems may be exacerbated if damage from worms is
Classification of old horses with respect to their nutritional needs. Apparently ‘Normal’ the horse that is old in years but has no apparent age-related or veterinary conditions and is still being ridden or breeding. With good worm, vaccination and dental care, these horses maintain condition on a standard balanced diet Apparently ‘Normal’ but overweight These horses often have little exercise and are easy-keepers. Weight loss management is required. Apparently ‘Normal’ but underweight These horses benefit from a general veterinary health check-up and a more energy-dense, nutrient-rich diet. Good options are soymeal, oil, good quality protein. The Geriatric Horse These horses have one or more abnormalities as well as old age. Veterinary diagnosis and support of underlying conditions combined with a palatable feed is the best strategy.
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present. This, along with teeth problems, is a major risk factor for choke and colic in older horses. Hay cubes and pellet feeds can be soaked in water to make a soft mash if choke or impactions are a problem.
MAINTAINING BODY CONDITION
Recent surveys have found that as horses age there is a reduction by owners in the preventive health care measures including vaccinations, farrier care and routine veterinary checks. Regular foot trimming and choosing a flat paddock, free from poaching and ruts, to decrease strain on joints PLUS regular blood work/ veterinary evaluations and monitoring can delay the beginnings and onset of common age-related conditions. And always choose companions carefully to avoid bullying. Continued
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NUTRITIONAL CHECK LIST
for the older horse
Protein…quality and quantity! Speed, strength and endurance decline with advancing years. This is partly because of a reduction in muscle mass, which results in a loss of muscle strength and is also due to a change in the ratio of muscle to fat, ie body composition and the all-important power:weight ratio. The amount of muscle is determined by the quantity and quality of the protein in the diet. In terms of ‘quantity’, horses require a certain number of grams of protein a day, not a % - % protein tells you nothing useful about the quantity or quality of the feed protein. If for example, a feed is 10% protein and a horse eats 3kg of the feed – the horse receives 300g of protein. If another feed is 20% protein and a horse eats 1.5kg, it still receives 300g of protein. The quality of protein is determined by its essential amino acid profile. The diet must provide all 10 essential amino acids because each tissue (liver, muscle, blood, bone etc) has its own specific recipe of amino acids. For muscle, the most important are lysine, threonine & methionine.
Muscle building is so specific that if the feed meets the required levels of 9 essential amino acids, but has only half the tenth, body protein synthesis may be reduced by up to 50%. It’s a bit like making a cake – if you want a chocolate cake you need cocoa. Once that runs out, production of chocolate cakes stops, regardless of how much sugar, eggs, flour etc you have. Similarly, once the body runs out of an essential amino acid, the production of new cells that require that ingredient, stops. So regardless of the % protein of a feed, if there is not enough of each essential amino acid, a limit is placed on protein synthesis - the other essential amino acids cannot be used and are stored as fat. When this occurs, horses will lay down ‘cover’ (fat) at the expense of muscle, blood and bone. And, it means that even if a feed is 50% protein but doesn’t contain all essential amino acids, it may only be 10% useable to the horse.
Oils Omega 3 oils have been found to benefit blood oxygen levels and reduce the incidence and severity of arthritis and inflammatory skin conditions in both humans and animals. A small amount of omega 3 oil per day could provide benefits for the blood and immune system in older horses. Oils are also excellent for maintaining body weight, reducing heat production during exercise and increasing energy intake. Horses may require 21 days to adjust to a fat-supplemented diet. Adding oil to the feed often improves palatability and absorption of vitamins A and D, essential fatty acids, and help reduce dust and fines.
Which oil and how to feed: Because blood insulin and sugar levels are steadier and less variable when oil is a major source of energy, increasing oil intake brings many benefits. Omega 3 oils suppress inflammation associated with ageing, have anti-clotting and immune support actions and can April May 2021 - Page 20
Algebra - retired 24 year old. Enjoys his box at night and prefers to stay in on days when there is inclement weather. Photo Julia McLean
Table 1. Amount of feeds that can be replaced with 1 cup (250ml) of oil Oats
700g
Barley
600g
Corn
600g
Commercial grain mix
630g
Rice bran
450g
Flaxseed
600g
Table 2. Omega 6 and Omega 3 levels in common feedstuffs Feedstuff
Omega 6 (Linoleic acid)
Omega 3 (Linolenic acid)
Lucerne hay
3.9
7.9
Canola meal
12.1
3.5
Barley
10
1
Flax seed
59
226
Linseed meal
2.1
7.3
Oats
23
1
Rice bran
71
3
Soy meal
5.9
1
Sunflower seeds
230
0.6
Canola oil
186
91
Coconut oil
18
0
Fish (salmon) oil
17
10
Linseed oil
127
533
Olive oil
98
7.6
Peanut oil
320
0
Rice bran oil
334
16
Soy oil
504
68
Sunflower oil
289
0.4
Several factors need to be considered when supplementing oil: • horses need up to 4 weeks for their gut to adapt to added oil • start with total daily addition of 50ml and increase by 10-20ml per day muscles need 6 to 11 weeks to adapt - begin well before a strenuous event.
improve insulin sensitivity. These advantages apply to all horses and especially ageing horses. They have also been shown to delay the decrease in red blood cell flexibility in athletic horses. Oils provide around 3 times as much energy as grains – so 330ml of oil provides the same amount of energy as 1kg of oats – but without the risk of ‘hot’ behaviour and hind-gut acidosis (Table 1). In fact, adding oil to the diet provides benefits for all horses in terms of acidosis, arthritis, behaviour, fertility, inflammation, immunity, PSSM, temperament and tying-up.
The addition of 500-1000ml of oil to the diets of performance horses reduces heat production, weight handicap (from gut fill), working heart rates and can delay the onset of fatigue. Oil provides a cool and steady supply of energy - allowing the horse to preserve blood glucose levels. The ‘glucose-sparing’ effect of oils delays the onset of fatigue, so that although horses cannot increase their maximum effort, they can maintain it for longer. The health benefits of increased omega-3 fatty acids in human diets are widely accepted and human athletes on omega 3 supplements report less muscle soreness and shortened recovery after athletic events. Studies in horses have found advantages in feeding diets rich in omega 3 including: lowered heart rates, lowered joint inflammation and increased immune response and disease resistance. Omega-3 fatty acids have also received attention for their role in maintaining cell membrane fluidity (including red blood cells) and are thought to reduce exercise-induced pulmonary haemorrhage – ‘bleeding’. So, which oils to choose? Most diets are based on cereal grains, which are rich in omega 6 oils. The natural, grazing, browsing horse has a diet based largely on grass and browsing forage that contain a much higher proportion of omega 3 oils. The PUFAs in corn, sunflower, safflower, soy and rice bran oil are mainly omega 6, which tend to aggravate inflammation. Vegetable oils with higher concentrations of omega 3 fatty acids include linseed, flaxseed and fish oil (Table 2).
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Oils with a high level of omega 3 fatty acids don’t intensify inflammatory processes – in fact, they reduce them. All content provided in this editorial is for general use and information only and does not constitute advice or veterinary opinion. The content does not consider individual circumstances, is not intended as a substitute for advice, and should not be relied upon as advice or in place of consultation with your equine veterinarian. For full disclaimer, please refer to our website: www.jenquine.com.au Dr Jen Stewart is currently the only practicing equine veterinarian and clinical nutritionist in Australia with more than 40 years experience. Jen has been developing premium formulas for studs, trainers and feed companies - such as Mitavite - in Australia and around the world. Consulting to leading international studs and trainers in various countries while working on research projects and being involved in nutritional management of a variety of equine clinical conditions, including colic, tying-up, laminitis, performance problems, developmental orthopaedic diseases and post-surgery. Jen’s vision is to provide a world best-practice in equine veterinary nutrition and to BRING SCIENCE TO YOUR FEED BIN.
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