Many trainers have had a greyhound which has exhibited signs of severe distress and even collapse within the few minutes after a fast or longer distance race. In some cases, the animal may experience a short episode of inability to walk or coordinate its limbs, muscle trembling and weakness and be unaware to its surroundings.
A few may develop more severe symptoms of elevated heart and respiratory rates, where the heart can be seen pounding inside the chest cavity and the rate of breathing in unison with it.
Many trainers describe this more extreme form as the ‘thumps’ because the greyhound’s heart appears to ‘thump’ within the chest.
These signs, weakness and collapse are referred as Post Race Distress Syndrome which as a number of forms and severe outcomes.
A small number of greyhounds may be so weak after a strenuous race that they have to be supported by cradling the arms under them and be helped off the track by their handler until they regain the strength to stand by themselves in 3- 4 minutes after the race finish.
It is also well established that greyhounds which over-exert themselves in a race, but appear to recover initially well, may develop severe dehydration, muscle wastage and weight loss within 12-36 hours and are at risk of dying unless intravenous fluids and electrolytes are given promptly under veterinary supervision.
New Research Studies
There are two research projects under way to try to find the underlying cause for Post Race Distress Syndrome or PRDS.
One research study being funded at the University of Melbourne Vet School in Aust-ralia to investigate the circumstances which have an influence on the development of PRDS in greyhounds after a hard race.
Many specialist greyhound veterinarians are also providing clinical observations to the research group in order to further the understanding of the syndrome.
Although some believe it is not a good image for greyhound racing to have animals collapse after a race and some actually die, a better understanding of the underlying causes is important to reduce the incidence and make greyhound racing the thrilling, family sport that distinguishes it from horse racing.
In the UK, Dr Richard Payne, an Honorary Senior Fellow at the University of Liverpool School of Vet Science and a well respected greyhound specialist, is also conducting research into PRDS and other problems affecting greyhounds after racing.
His research is continuing and if you have a greyhound which has exhibited PRDS, then I am sure that Dr. Payne would be interested in talking to you and your vet.
Possible Underlying Causes of PRDS
Until the results of the research study findings are available from the University of Melbourne’s and Dr Richard Payne’s work at the University of Liverpool are published, the exact cause or multiple causes are not known.
However, there are a number of influencing factors which can contribute to PRDS.
Changing Weather Conditions
It appears that the weather conditions, especially warm humid conditions may increase the risk of PRDS , although there are also reports that a sudden cold snap in the days leading up to a race may influence the onset of PRDS.
One observation in Australia has suggested that a drain of energy due to excessive panting under hot conditions or long distance travel prior to racing, may sap energy levels and increase the risk of PRDS.
This is also possible scenario during a pre-race cold snap. It has been suggested that providing more fat as an energy boost prior to racing may help reduce the incidence of PRDS.
One of Australia’s successful owner/trainers and an experienced greyhound veterinarian, Dr Jane McNicol, suggests that adding 100-120g of meat trimming fat, lard or suet to the ration daily in the pre-race period during a cold spell may help offset the energy loss associated in some cases with PRDS and enable a greyhound to race without developing the syndrome.
Greyhounds are only the one anaerobic sprint racing animal which can use fat for energy even at full race speed.
In fact, Dr McNicol has found that simply adding 100g of fat to the ration can sometimes help a 450metre greyhound run and win over 520 metres by providing the added energy it needs to fuel the extra distance.
A less than adequate energy intake would otherwise be a limiting factor in a traditional lean meat and dry food racing diet.
Providing an antioxidant supplement may also be beneficial in this case to assist muscle cell walls cope with the high oxygen diffusion rates and the increased aerobic metabolism of the fats for energy.
Dehydration
If a greyhound runs a race in a dehydrated condition, is likely to increase the risk of metabolic stress, cramping and PRDS.
Although more research needs to be carried out to determine the influence of dehydration on PRDS, in my experience, an excitable, dehydrated greyhound is a candidate for post race stress and even collapse.
In fact, observations of racing performances suggest that even mild dehydration ,with a body weight loss of 1kg -1.5kg by the time a greyhound races after a long wait in the race day kennels, can reduce performance by 3-10 lengths over 500 metres and increase the risk of metabolic problems, including PRDS, cramping and the ‘thumps’.
Anaemia
If a greyhound is anaemic when raced, oxygenation of the muscles and tissues at racing speeds is likely to be reduced, increasing the likelihood of lactic acid build up in the muscles and early contraction fatigue, with a corresponding drop off in performance.
Blood tests of greyhounds with symptoms of PRDS have found that many have a low bicarbonate reserve in the blood due to lactic accumulation in the tissues and some are also anaemic or have a red cell count below7.5 measuring units and Packed Cell Volume (haematocrit) below 55% at rest.
The fluid shift into the blood which occur at the start of a race and contraction of the spleen to release red cells is designed to carry more oxygen by keeping the blood in a consistency which will perfuse the muscle cell walls and deliver oxygen to fuel rapid contraction.
In a greyhound which is already dehydrated or anaemic before a race, the risk of metabolic and circulatory stress is increased and could trigger a post- race exhaustion or cramping attack, or PRDS.
Studies of greyhound exhibiting PRDS in Western Australia have found that ‘hypoxia’ or a low blood oxygen level, is not a common post race finding in greyhounds which collapse.
However, in an emergency, administration of oxygen by way of a mask appears to be helpful to revive the animal.
Electrolyte Disturbances
Until the findings of the Melbourne study and Dr Richard Payne’s observations are available, it is common belief that electrolyte disturbances are not a trigger for PRDS, although some greyhounds have been found to have a lower than normal blood calcium level, which is also a common finding in the immediate post race period in many well performed greyhounds.
In the interim until the underlying causes can be found, most veterinarians recommend that greyhounds are supplemented with calcium, magnesium, electrolytes, and antioxidants in the pre-race period, with additional fat under cold conditions or extremes of heat, in the 2-3 day lead up to a race to help reduce the risk of PRDS.
