Over the last decade, the sport of greyhound racing has become a more universally accepted pastime in many countries. The number of greyhounds that are engaged in competitive lure racing between 15 months and four years of age is now estimated to be in excess of 150,000 worldwide, with an equal number of greyhounds as growing puppies, brood bitches and stud dogs.
These statistics are based on estimated populations, with the largest numbers of greyhounds in America, followed by Australia, United Kingdom, Ireland, New Zealand, Sweden, Germany and to a limited extent in Italy and Spain. Most recently, greyhounds have become more popular in mainland China. Once their racing careers are over, it is estimated that over 40,000 retired greyhounds are living in luxury as household pets in North America, the United Kingdom and Australia under greyhound adoption schemes promoted by animal welfare organisations.
The popularity of lure racing over set race distances on straight or circle tracks has influenced the way greyhounds are selected, trained, housed and fed, as compared with the original coursing bloodlines (Kohnke, 1998). Greyhounds must to be maintained within an established race weight range based on their body weight within ± 1 kg of their last winning trial or race weight. A nutritionally adequate and well balanced diet is paramount to the health, performance and adaptation of the greyhound to the physical and metabolic stresses of racing.
Although diets were traditionally based on fresh red meat and cereal meals, with disease risks such as BSE and Foot and Mouth Disease in the UK and Europe, and the increasing cost of beef and other meat in affluent countries, there has been a change in the staple diet for racing greyhounds to compounded dry foods formulated to partly or fully replace meat, with only a limited amount of meat, offal, meat by-products and processing trimmings added to complete the diet.
A number of extensive reviews on the traditional methods of diet composition and practices for the feeding of racing greyhounds have been published over the last two decades (Grandjean, 1988; Kohnke, 1989; Grandjean, 1991; Grandjean and Paragon, 1992, Grandjean and Paragon, 1993; Kohnke, 1994; Britton, 1994; Blythe et al., 1994; Reinhart, 1995; Kohnke, 1998). However, the feeding of greyhounds remains one of the areas of animal nutrition still heavily influenced by tradition and folklore. Today an increasing degree of science, combined with the ‘art’ of feeding dictated by time honored practices is used in feeding racing greyhounds.
The racing diet for successful competitive racing has been refined since lure racing became the industry standard for grading wagering odds relative to body weight and performance. In addition to maintaining health and vitality by the provision of a diet adequate in energy, protein, fat, fiber and other nutrients, as is required by the canine species generally, there are a number of important performance related nutritional and management criteria that should be adopted.
PROVIDE A LOW BULK, HIGHLY DIGESTIBLE RATION
Gut fill and body weight has a large influence on speed and ultimate performance in a greyhound running over distances between 300-700 meters. The traditional meat-based diets with an intake of 1000 g daily containing an average of 50-70% fresh red meat by weight or 500-700 g for an average 30 kg (66 lb) greyhound, combined with 30-50% of a low protein, low fat dry food or kibble (300 g daily) are still popular. However, these feed combinations may be excessively bulky for greyhounds to consume, especially as it is often fed as a single meal daily. The actual dry matter content of raw meat in the fresh state is only 20%, with water contributing the major portion of the weight and bulk.
The advent of low bulk, highly digestible extruded dry foods manufactured on a cereal and oil seed meal base, with high fat (20-30%) and high protein (20-30%) as the major energy and protein sources theoretically distends the gastrointestinal tract to a lesser extent and are digested leaving a minimal bulk of stool. However, low bulk complete feeds have not been well accepted in greyhound kennels because of a preference for traditional meat-based feeding practices, as well as the higher cost of these dry foods (Table 1). Even dry foods processed by steam extrusion that are designed to facilitate a reduced feeding rate of 250–300 g daily for each meal to meet nutrient requirements at a predetermined body weight, have not been widely accepted.
The negative aspect of a high protein, high fat, minimal bulk diet is that many trainers think it leaves the dog appearing hungry rather than full and content when fed once daily on a more bulky meat-based diet. The positive benefit of a low bulk, highly digestible diet is the lower stool bulk, which reduces kennel and turnout clean up time and less faecal odor in kennels when fresh meat is eliminated from the diet (Kohnke, 1998).
In countries with a warm climate such as Australia, the amount of water consumed to maintain hydration can negate any weight benefit obtained from feeding low bulk, high protein and high fat dry foods.
Various studies have found that high protein dry foods may be detrimental to speed and performance. On average, a racing greyhound is able to run 0.1 m/sec faster (about 2 lengths of the winning margin) over 500 meters when fed a moderate protein diet (20-25% crude protein) as compared to a high protein diet containing in excess of 30% crude protein (Waltham, 2000). These studies concluded that a dry food based diet, which contained 42% of the energy from carbohydrates, 33% from fat and 24% from protein, provided the best dietary balance to optimize speed and performance over a standard 500 meter race distance. However, greyhounds on this diet were slightly heavier in body weight than greyhounds fed a diet containing higher protein and fat with a lower content of carbohydrate. This difference in body weight was attributed to a greater muscle bulk in greyhounds fed on the medium protein diet.
The traditional meat-based diet contains a higher level of carbohydrates provided by cereals, rice or bread (Kohnke, 1998). Another study suggested that greyhounds run faster race times when meat was added to a low protein and semi-lean diet, presumably because the meat provided extra fat as an energy source (Waltham, 2000).
PROVIDE AN ECONOMICAL AND PALATABLE RATION
The prize money pool and wagering on greyhound racing as part of the code of racing in most countries is much lower than that provided by horse racing.
Table 1. Classes of dry foods for racing greyhounds relative to meat content in diet.Adapted from Kohnke (1998).
The cost of purchasing, housing, feeding and training a greyhound, although low in comparison to the purchase, upkeep and training costs of a horse, is actually higher in proportion to the return from prize money in most countries.
The high energy density of fat and the lower cost of freshly trimmed and rendered animal fat byproduct of the beef, sheep, pork and chicken meat industries, makes the combination of a fat-boosted minimal meat and commercial dry food diet more economical as well as more palatable to racing greyhounds. Therefore, there is an increasing tendency to feed a minimum meat diet, higher in fat and protein, to reduce feeding costs.OPTIMUM MINERAL, TRACE MINERAL, VITAMIN AND ELECTROLYTE SUPPLEMENTATION
The provision of nutritional supplements to correct low, imbalanced or inadequate levels in meat and cereal-based dry food rations is paramount to meet the elevated needs for minerals and electrolytes imposed on the musculo-skeletal and metabolic system by racing. When trained and fit to race, a sound greyhound can be successfully raced twice weekly. Adequate intake of minerals for bone development on a meat-based diet is particularly important to maintain skeletal strength (Kohnke, 1998).
It is estimated that the daily calcium intake needed by a sedentary 30 kg dog to maintain optimum skeletal strength is 357 mg (NRC, 1985), compared to 6000-8000 mg daily for a greyhound in full race training (Kohnke, 1998). It is also recommended to add 20% more vitamin D than NRC (1985) guidelines to dry food formulations; as cereal based dry foods, even with added calcium, have been associated with an increased incidence of bone fractures (Kohnke, 1998). The estimated requirement for most other minerals and trace minerals is 2-3 times higher in a racing greyhound as compared to a resting dog (Kohnke, 1998).
Recommendations for B vitamin intake and fortification of feed is at least three times higher than NRC (1985), which reflects the higher metabolic rate during anaerobic exercise of a racing greyhound (Kohnke, 1998; Table 2).
Demineralisation of skeletal and joint structures as a result of high-loading athletic exercise and cortisone-induced muscle catabolism during exercise and respiratory lead to losses of fluid and complementary electrolytes, particularly potassium. The diet must be fortified with a large range of macro and micro nutrients to meet athletic demand and maintain body reserves, optimum metabolic function and racing soundness.MAINTAIN IMMUNE COMPETENCY
It is recommended that the ration provided for racing greyhounds contain additional nutrients such as vitamin A, vitamin E, vitamin C and selenium to counteract immune suppression resulting from higher circulating cortisol levels in greyhounds subjected to the stress of training and racing. This will help to maintain optimum resistance against disease and assist recovery from racing and injury (Kohnke, 1998).
Although greyhounds perform over relatively short distances in lure races, the effects of physical stress are often more marked than in horses or human athletes. Conditions such as diabetes insipidus (referred to as water diabetes or racing thirst) are precipitated by racing under hot or environmentally stressful conditions or by the extreme physical exertion following a fall or interference in an effort to catch the race field. Cramping, referred to as hypoxic or exertional rhabdomyolysis, with muscle seizure under stressful conditions, is a universal problem in racing greyhounds. It is associated with an imbalanced electrolyte intake and excessive loss of potassium, high cereal starch diets and racing under cold conditions without adequate warm-up.MAINTAIN ADEQUATE HYDRATION
Other conditions, which can be largely overcome by providing an adequate, balanced and well hydrated diet include exercise hyperthermia, which can result from overheating under hot conditions and acute rhabdomyolysis related to severe overexertion in a dehydrated greyhound. These can both be fatal within 48-72 hrs unless intensive therapy is administered. Supplements of vitamin E, selenium and other trace minerals preferably in organicallycomplexed bioavailable form B vitamins and vitamin C are widely recommended in conjunction with a balanced, but low, sodium intake (greyhounds do not sweat) and adequate potassium supplementation in a moistened diets to ensure hydration. These measures will help maintain an active immune response, appetite and avoid dehydration.
Table 2: Recommended daily intake (RDI) for a 30 kg resting and racing greyhound on a combined meat and dry food diet.To enlarge the image, click here
Adapted from Kohnke, (1998)
The other major problem to which greyhounds are commonly subjected is the consumption of highlycontaminated meat containing potentially pathogenic Salmonella and E. coli bacterial species. The widespread use of 3-D (debilitated, diseased or dying) and 4-D meat (add dead to 3-D specifications) as a base for greyhound diets in the US because of economic considerations increases the bacterial challenge to the gastrointestinal, immune and hepatic systems. Greyhounds often develop bacterial diarrhoea and associated dehydration when contaminated meat with a high microbial count is fed.
There is also the risk of antibiotic residues being excreted into the urine. These residues can be detected as prohibited substances on race day in greyhounds fed meat from animals treated with antibiotics and other drugs prior to slaughter or death. The adoption of a complete dry food diet eliminates these risks in greyhounds raced on a regular weekly basis.
ConclusionGreyhounds are elite athletic animals that are subjected to extreme physical exertion during racing and the cumulative effects of environmental, metabolic and physical stress when trained and raced on a regular basis. They must be provided with a palatable, low bulk, high energy-dense ration, with a medium crude protein and fat content to maintain competitive speed and stamina within set limits of body weight. An adequate intake of minerals, trace minerals, electrolytes and vitamins to correct low, imbalanced or inadequate levels in meat-based diets, in particular, is essential to maintain musculo-skeletal soundness, optimum metabolic activity, strong immune status and overall health in greyhounds racing between a relatively young age of 15 months to a mature age of between 3 and 4 years.References
Author: JOHN R. KOHNKEJohn Kohnke Consultancy Pty Ltd, Rouse Hill, NSW, Australia
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