Racing greyhounds, in common with other animal and human athletes, can suffer from stress as a result of their highly motivated effort , extreme metabolic and physical demands during racing.
Some of these less acute stresses can be observed after a hard race, with heavy panting to re-oxygenate their system and blow off heat, physical injuries, such as sprung toes and torn muscles, as well as metabolic stress including cramping and the ‘thumps’’.
In some greyhounds, the physical stress is cumulative, with signs of hair loss, such as ‘bald thigh syndrome’, loss of appetite, weight loss and reduced speed and overall performance over a period of time.
In this article, we will discuss an example of an acute and severe stress-induced syndrome, such as Exertional Rhabdomyolysis, as well as a sign of chronic long term stress, often manifested by the development of hair loss on the sides of the chest and thighs, or what is commonly referred to as ‘bald thigh syndrome’.
Many of these stress conditions can be avoided by careful training, regular rest periods and good health and feeding management.

ACUTE ACIDOSIS SYNDROME
The term ‘acute acidosis’ is used to describe the more severe form of muscle dissolution or ’meltdown’, with acute cramp–like symptoms which are associated with Exertional Rhabdomyolysis (ER) in a severely stressed or dehydrated greyhound following an overly strenuous trial, course or race. The extreme form is luckily not a common problem and it can occur in other breeds of working dog as well.
Acidosis is a term used to describe soreness and swelling (‘blowing up’) of the backline and hind limb muscles following sprint exercise and racing in an otherwise healthy, greyhound. It is a natural, transient condition which is related to fast, anaerobic (oxygen debt) exercise in all greyhound athletes.
Predisposing Causes
The rapid build-up of L-lactic acid is a result anaerobic metabolism in rapidly contracting muscles as a result of low oxygen supply to the major back and hind limb muscles of a galloping greyhound. It is more likely to occur if the greyhound is anaemic, dehydrated or not fit enough for the speed and distance of the race, or runs an extra ‘lap’ after a trial or race.
It is not the underlying cause of cramping, although ‘cramped’ muscles show typical symptoms because the accumulated lactic acid is retained in the contracted muscle tissue and cannot disperse into the surrounding tissue or blood.
Anaemic greyhounds are prone to acidosis because of poor oxygen delivery to contracting muscles, as are dehydrated animals where blood perfusion and muscle oxygenation is impaired at sprint speeds.

Typical Signs
Greyhounds exhibit swelling, soreness and discomfort of the backline and rump muscles within minutes to up to 24 hours after the race as a result of water being transferred by osmotic gradient into the highly acidic muscle environment.
In the acute form associated with Hypoxic or Exertional Rhabdomyolysis, the muscle cells swell and rupture, causing severe muscle damage and escape of muscle enzymes and myoglobin pigment into the blood and overflow of myoglobin into the urine, to produce  ‘port wine’ coloured urine and severe dehydration.
ER causes extreme pain, loss of muscle mass due to severe muscle damage and dissolution, and can be follow racing under extremely hot conditions, a concurrent high temperature in a sick greyhound which is allowed to race, dehydration and acute electrolyte disturbances, particularly the chronic depletion of blood and muscle potassium levels due to chronic muscle soreness, barking, panting and the use of high doses of urinary alkalinising products.
If the symptoms of ‘acidosis’ persist for more than 12 hours, and are associated with muscle ‘meltdown’, severe weight loss, listlessness, collapse, dehydration and passing of dark urine (myoglobin pigment excretion), the greyhound must be referred to a veterinarian for emergency fluid, electrolyte replacement and other anti-stress medication.
Management
All fit and healthy greyhounds suffer a mild acidosis during the final stages of the race, but where greyhounds are not prepared adequately by sprint training, the accumulation of lactic acid occurs earlier and to a greater degree in anaerobic environment of rapidly contracting muscles.
Ensuring the greyhound is provided with a balanced diet, including supplementation with 100-150 IU of vitamin E daily, avoiding anaemia and maintaining adequate hydration and electrolyte balance, will all help reduce the risk in an otherwise fit greyhound.
Walking the greyhound for 10 minutes after sprint exercise and racing where possible to dissipate lactic acid out of the muscle environment is helpful in avoiding the mild condition.
Supplementing with citrate based muscle ‘buffers’ in the feed or over the tongue, is considered to be helpful in neutralising excess blood and muscle lactic acid accumulated after sprint exercise. However, excess amounts must be avoided as elevated blood alkalinity can result in fluid and electrolyte shifts and predispose to cramping and poor performance if potassium salt is leached out in the urine.

BALD THIGH SYNDROME (BTS)

BTS is a relatively common problem, particularly in older male racing greyhounds, with thinning and symmetrical loss of hair covering the sides of the hind limbs (thighs), chest and belly over a 4-6 week period.  These symptoms often become apparent after returning to racing after a rest period.  It affects up to 25% of racing greyhounds in long term training.  Some kennels have a higher incidence, which may reflect on training methods and physical stress, the diet or environmental conditions.
Predisposing Causes
The exact cause has not been determined, but the symptoms are similar to those of either chronic dehydration or stress related due to the continued production or over-secretion of cortisone by the adrenal gland.  For many years, it was proposed that low thyroid activity was a common underlying cause, but this has now been disputed by careful testing of thyroid hormone levels, although in many cases, thyroxine hormone was administered orally with some apparent success.
The symptoms should not be confused with hair loss by abrasive concrete floors, or hessian (burlap) bags used as a bed mattress cover, which can also shear off hair on the thighs as hair becomes trapped in the open weave.  However, in this case, it is normally more pronounced on one side and the skin is smooth ‘shaven’, rather than being wrinkled and dry in appearance.

Typical Signs
In most cases, the affected greyhound appears healthy, eats well and is bright and alert in early training. However, over a 4-6 week period, the skin develops a wrinkled, leather-like appearance and appears to darken as the hair thins out on the thighs, elbows and chest.
Often the greyhound loses weight and develops a chronic dehydration over an extended period in training, with symptoms of ‘training off’ and loss of speed and stamina after 4-6 consecutive races.
Affected greyhounds lose interest in chasing and run back in the field.  If the greyhound is given a lay-off for 2-3 weeks, it will often regain form or 2-3 races, then lose performance again.

Management
Often a 3-4 week lay-up from training will enable the hair to regrow, combined with increased intervals between racing once the greyhound returns to training, will help reduce stress.
Although for many years, long term courses of thyroid hormone (thyroxine 200 ug tablets) was recommended under veterinary supervision, and still is in some cases, it is now recognised as a stress-induced condition which responds to a let-up in strenuous racing and dehydration therapy.
It must be given in conjunction with potassium salts and increased fluid to soak the dry food to counteract dehydration for best results.
I always suggest a reduction in the distance of walking to 1-2 km per day, with sprints over 200 metres twice weekly between races at 10-14 day intervals to reduce the physical stress. It is best to keep the greyhound ‘fresh but fit’ between races.
Various ‘hair growth tonics’ are promoted to assist hair regrowth, but these generally improve the health of the skin rather than stimulate hair regrowth on the thighs and chest.