In the fall of 2000, Dr. John Berezowski of the Western College of Veterinary Medicine (Saskatoon, Canada) sent out a survey to identify what diseases affect the deer industry in Canada and the United States. Some 167 deer/elk farmers (32% of the total sample) and 8 veterinary labs returned the surveys. The total numbers of deer/elk upon which the results are based was approximately 5,200.
The study found the following death rates – 22% among fawns, 5% among yearlings and 4% among adults.
Deaths occurred during birthing – 2.9% among adult does, 2.2% among yearlings and 27% in assisted births. Assistance is necessary during problem births, so it should be expected that there will be some mortality.
The study found that fawn survival rates were 89% to one month, 82% to weaning and 78% to one year of age. When fawns die, some 49% do so within the first month. From a production standpoint, care for fawns during their first month is critical to ensure high survival rates.
According to this study, there were two major causes of death in deer and elk – emaciation and trauma.
The major causes for emaciation were:
- improper nutrition
- parasites – brown stomach worm (important to de-worm)
- behavioral causes – the “pecking” order
- problems with teeth
- unspecified disease
- capture myopathy
- MCF – possibly a new strain of virus
- grain overload
- other – usually some infectious diseases
The study found that deer and elk farmers need to pay more attention to handling of animals. Too many animals are injured or killed during handling. Farmers must have facilities that reduce risk of injury or death to the animals. Training is also important – for both the farmers and the animals. “Trained” animals are easier and safer to handle.
The study found that mortality due to capture myopathy was 6% among fawns, 12.5% among yearlings and 20.6% among adults.
Capture myopathy (or white muscle disease) is a response by the deer to stressors in its environment. The type of response to stress is affected by several factors – species, age, previous experiences, general health, genetics and learned/innate behavior.
The immediate reaction to stress is the “fight or flight” syndrome. The adrenals secrete adrenaline. Persistent stress raises reaction to a dangerous level.
The mid-term effects of stress are: a) release of ACTH from the pituitary gland, b) the animal is on high alert, c) the animal becomes worn out, and d) the deer becomes susceptible to disease.
Severe stress over days or weeks can cause chronic corticosteroid production and adrenal exhaustion. The secondary effects include metabolic upset, loss of body condition, loss of reproduction, and increased susceptibility to stress and death.
Stress causes anaerobic metabolism, which results in chemically stored energy, lactic acid and cramping and muscle damage. Lactic acid damage contributes to capture myopathy.
Capture myopathy is a syndrome of acute or chronic degradation resulting from stressful activity such as a pursuit of the susceptible animal. It can occur without exercise (animal does not have to be chased). Capture myopathy can occur both during physical and chemical restraint. It occurs in most animals, but especially in ungulates. It has been reported in birds and even fish.
Fear and anxiety plus excessive body heat plus too much adrenaline will result in capture myopathy.
The clinical signs of capture myopathy include sudden death within 24 hours, depression, rapid shallow breathing, and failure to recover from anesthesia. Death can occur after several hours of symptoms, or from cardiac arrest. The animal may also appear to recover, but has heart damage. It may die at the next stressful event.
Other symptoms include stiffness or lameness, swollen muscles and brown urine (due to myoglobin excretion which may lead to damage of the kidneys).
There is no treatment for capture myopathy. Therefore, prevention is critical. This can be done through good planning, good facilities and trained animal handlers.
Minimize the time of restraint. Some vets use anti-psychotic handling drugs. Long lasting tranquilizers are useful for translocation and prolonged handling. Keep the duration of immobilization as short as possible, and reverse it.
Selenium and Vitamin E deficiency can contribute to capture myopathy. Be sure that your animals are getting adequate amounts in their diet.
Don’t handle or immobilize animals in the heat of the day. This significantly increases the risks. Also, if you have to redo immobilization, then just quit, the risk is too great.
Good production and management techniques require the minimization of animal mortality. Addressing the issues discussed will assist farmers to increase production and the profitability of their operations.