The Impact of Nutrition and Feeding Practices on Equine Behaviour and Welfare
Equine Studies Group, Waltham Centre for Pet Nutrition, Leics, UK
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There is considerable variation in the management and feeding practices of the domestic horse across the world (Harris, 2000). This reflects their historical use and management, their current role, and the availability and cost of suitable environments and feedstuffs. To what extent these practices simulate a natural environment varies with each geographical location and the purpose for which the horse is kept (e.g. horses in Australia or North America tend to be managed on pastures to a greater extent than those in Northern Europe). This management factor has an impact on welfare, indicated by the lower incidence of Recurrent Airway Obstruction for which one of the exacerbating factors is poor stable ventilation and dusty bedding and hay. In addition to the available resources, the desire for convenience to the owner/manager and a perception of increased efficiency influences how the horse is managed.
In an ideal world all horses would be given 24-hour access to appropriate grazing, the constant companionship of con-specifics and freedom to procreate. However such liberty would seriously limit their usefulness (perceived and actual) to the majority of horse users. Limiting the uses for which horses can be kept may result in an increase in the number of abandoned/euthanized horses or a decline in the domestic horse population. It may be that fewer horses kept in optimum conditions is far more desirable than many managed sub-optimally, though there is room for debate around the definition and range of sub-optimal conditions and their real effects upon the well-being of the horse. It is probably more realistic that we strive to strike a balance between the physiological and psychological needs of the horse and the needs of the user.
This abstract highlights a few of the areas in which nutrition and feeding practices impact on the behaviour and welfare of the horse.
Nutrition and Feeding Practices Impact on Welfare
The horse has evolved specific digestive physiology and anatomy around its natural diet (i.e. high fibre grazing and browsing) and feeding behaviour of “trickle feeding” for long periods (Harris, 1999a). Any animal kept under unnatural conditions, such as being stabled and offered high cereal, large volume infrequent meals may have their welfare compromised. For example, the horse only produces saliva when it chews – the saliva lubricates the passage of food and buffers the acidic environment of the stomach. Feeding the horse large, cereal-based, discrete meals has an effect throughout the digestive system due to the low fibre and high hydrolysable carbohydrate content. Undesirable consequences include a reduction in the amount of saliva produced, which would allow the stomach to remain more acidic for longer and, therefore, may allow undesirable, gas-producing bacteria to survive (Meyer et al, 1975; Harris, 1999b) The larger volume will mean that the food is pushed through more quickly to the small intestine and hind-gut, increasing the risk of gastrointestinal disturbances due to changes such the lysis of certain bacteria releasing endotoxins which may be absorbed, increasing the risk colic, diarrhoea and laminitis (Harris, 1999a).
There are many areas of concern which are either directly caused, are exacerbated by or could be improved with nutrition and/or particular feeding practices (Davidson and Harris, 2002), such as:
General Inappropriate Nutrition
Any horse whether it is a healthy adult horse or a “vulnerable” horse (i.e. those going through a “stressful” period, e.g. neonate, foal, weanling, pregnant or lactating mare, senior, performance horse) can be at risk if the appropriate nutrition is not offered. Different lifestages, horse types, disciplines and workloads have different nutritional requirements. Horses need to have their diet tailored and changed as their role changes, and while each discipline has traditionally dictated how the horse is managed and fed, we should discourage any practices that require the horse to be maintained outside a healthy range or beyond its inherent ability. Two examples are ponies and foals: Ponies are often allowed to become obese and are then put on starvation diets – this “see-saw” feeding can be dangerous and puts the pony at risk of conditions such as laminitis and hyperlipaemia. Developmental Orthopaedic Disease (DOD) in young horses, while multifactorial, is thought to be exacerbated by feeding inappropriate and unbalanced diets to promote fast growth rates (Kronfeld et al, 1990; McIlwraith, 2001).
High Cereal/Low Forage Diets
The welfare implications of feeding high cereal/low forage diets are immense and beyond the scope of this abstract, but in short, the horse’s digestive system has a finite capacity for hydrolysable carbohydrates. Feeding large quantities of cereals has been linked to a number of conditions, e.g. laminitis, gastrointestinal disturbances, gastric ulcers and oral stereotypies. There are two particularly vulnerable members of horse society – racehorses and foals. Thoroughbred racehorses tend to be stabled for very long periods, have limited access to grazing and are fed low forage/high cereal diets, this is reflected in a higher incidence of gastrointestinal ulcers (Murray et al, 1996) and behavioural stereotypies (Nicol, 1999) compared to horses of other breeds and disciplines. However, in order to fulfill their role they need high energy diets, one positive outcome of nutritional research is the role of supplementary fat (usually vegetable oil) as a means of providing more energy to horses without using cereals (Kronfeld and Harris 1997). As long as the diet is balanced for the additional fat, e.g. Vitamin E should be increased, there are thought to be a number of advantages including increased rate of fat mobilisation from the fat stores, glycogen sparing and better muscle glycogen utilisation during sprinting activities.
There is also a high prevalence of gastrointestinal ulcers found in foals, Murray (1989) found 51% of foals (< 3 months old) studied, showed lesions. While foals are not immediately associated with high cereal diets, there are a number of factors that impinge upon the foal’s well-being. A foal’s gastric mucosa is not fully developed at birth, making it susceptible to lesions. In addition, if foals have access to or are fed high cereal diets (e.g. the dam’s diet, weanling diets, or for fast growth rates) this can exacerbate conditions, add to this a stressful weaning and the foal’s welfare is at risk. Oral stereotypies, in particular crib-biting in adult horses, have long been associated with high cereal/low fibre diets (McGreevy et al, 1995). Recent work by Nicol et al, 2001 has shown that crib-biting in foals is associated with gastric inflammation and ulceration. It is crucial that we determine and encourage weaning and feeding practices that minimise this risk.
In the wild the horse forages (grazing and browsing) from a diet that varies daily and seasonally (Gill, 1988; Hansen, 1976; Ralston, 1984). Given the opportunity, and dependant on the quality and quantity of forage available, horses will feed for up to 16-18 hours a day (Avery, 1996; Nash and Thompson, 2001). Horses kept under restrictive conditions (e.g. monoculture grazing, stabling) have reduced opportunity to forage as well as a lack of autonomy over their food choice and a restricted and monotonous menu. In the stabled horses studied by Goodwin et al (2001), a preference was shown for the stable containing multiple forages versus the stable with only a single forage available. In addition, the horses in the single stable spent longer foraging in their straw bed and showed more behaviours that were indicative of food seeking. This has suggested to us that providing the horse with more than one source of forage will offer a more realistic feeding opportunity and may discourage unwanted behaviour such as bed-eating.
Recurrent Airways Obstruction (RAO)
There are many diseases that, although they will not be cured or prevented by particular feeding practices or nutrition, may be assisted if the appropriate dietary steps are taken. RAO (previously known as Chronic Obstructive Pulmonary Disease) is one such condition. The pathophysiology of RAO is not yet fully understood but is believed to be multifactorial. Subsequent obstruction of the airway is thought to be due to a hypersensitivity reaction to inhaled antigens. It can be exacerbated by specific allergens and non-specific irritants such as dusty bedding and hay. Research has suggested that oxidant/antioxidant imbalances may be involved in a number of conditions, including those that affect lung health such as RAO. Recently ascorbic acid (Vitamin C) levels were found to be lower in the lung Epithelial Lining Fluid (ELF) and plasma of horses with RAO compared to those of healthy horses (Deaton et al, 2001; Marlin et al, 2001). Kirschvink (2001) suggests that feeding an appropriate antioxidant cocktail may modulate the oxidant/antioxidant balance and airway inflammation, thus improving lung function of horses in remission.
Horses receive supplements for many reasons, e.g. to improve either perceived or real shortfalls in health, condition, behaviour or performance. If a well-balanced diet, tailored for the horse’s role is not providing all the nutrients that are required then correct supplementation may provide some benefits. However, there are a number of areas for concern. Additional nutrients may unbalance the diet, while any “super-dosing” of nutrients may cause toxicity issues. Many supplements have little or no proof of efficacy (Harris and Harris, 1998; Davidson, 1999), and have claims that are unsubstantiated. Possibly the two greatest welfare issues around supplements are the use of pain relief to enhance performance and the often indiscriminate use of behavioural modifiers. Pain management should be undertaken with the advice of a veterinary surgeon and the knowledge that pain often serves to prevent further damage being caused while the body repairs itself. As there are now many pain relief supplements, available over the counter, there is a great risk of abuse, through inappropriate usage.
The other supplement area of concern is the management of behaviour problems. Behavioural modification through both dietary intervention (e.g. supplements that induce sedation) and behavioural modification techniques (e.g. “flooding”) has increased exponentially, and is often carried out without the appropriate advice and by people with little or no understanding of the ontogeny of behavioural problems. The supplements available for behavioural modification, as with many others, have rarely been clinically tested and may in fact mask the problem or exacerbate it, and it is vital to determine the true cause of the problem as in many cases the source may be pain (Casey, 1999). While it may be appropriate and beneficial to make dietary changes (e.g. reducing the absolute calorie intake or the source of part of the calorie intake from hydrolysable carbohydrates to fat, increasing forage), diet is only one management factor that may need addressing. It is advisable that the determination of the problem and the subsequent treatment is carried out with advice from those trained in this field, otherwise the safety of people and the welfare of the horses may be compromised.
Good nutrition and feeding practices are essential to the well-being of the horse. While there are a few examples where nutrition will enhance the performance of a horse (although you cannot increase intrinsic ability), there are far more instances where poor nutrition may seriously limit health and potential. Any investigation into the welfare conditions of horses should include an evaluation of the nutrition and feeding practices. Conversely, the advice we give on what and how to feed horses directly impacts on their welfare and should be given with that in mind.
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