Reprinted from the Tracker, volume 5 issue 2, February 2001
Capture myopathy is a degenerative muscle condition seen occasionally in bison. This article explains the disease process, some of the risk factors, and gives some suggestions on how to prevent the disease.
Capture myopathy is a degeneration of the muscle fibres brought on by extreme muscle exertion and overheating. It is seen in elk, deer, and bison as well as other species. "Tying up" in horses and "Porcine stress syndrome" in pigs are similar conditions. Capture myopathy is associated with poor handling techniques that create a lot of stress and excitement in the animals. As our animal handling techniques improve, the incidence of this disease should decrease.
Under normal conditions muscles use sugar in the presence of oxygen for energy and produce carbon dioxide as a waste product. If the blood can supply the oxygen and remove the wastes fast enough, everything works smoothly. In situations where the muscles are working very hard, they use oxygen faster than the blood can supply it. This creates an oxygen deficiency. Instead of producing carbon dioxide, the muscles produce lactic acid. If the lactic acid builds up in the muscle cells it destroys cell membranes causing muscle damage and the release of cell contents. When enough muscle cells are damaged capture myopathy occurs. Death can occur from shock, electrolyte imbalances, or from muscle damage itself.
When people exert themselves they get a side ache or start to feel out of breath. They slow down or stop the activity. This allows the muscles to recover from the lack of oxygen. The heart pumps more blood to the muscles which supplies more oxygen and removes lactic acid. Animals that are fleeing from a predator or a perceived predator (you) don’t stop. They are convinced that you are about to kill them so they must do everything in their power to escape. In these situations lactic acid continues to be produced and the muscles continue to be damaged. Struggling while restrained can cause enough exertion to kill the animal. This condition was quite common in wild animals that are caught and transported thus the term "capture myopathy".
There are several factors that make animals more prone to developing capture myopathy. These factors include the following:
Heat - this can be from high outdoor temperatures in the summer or from the animal’s inability to lose heat. Elk or bison with a full winter coat can easily overheat on a warm winter or spring day because they are so well insulated. Animals that are tranquilized after running are also at risk of overheating because a sedated animal loses its ability to effectively dissipate heat.
Fear - not only does fear cause the animals to run or struggle but the fright hormones released can make the condition worse.
Diet - deficiencies in selenium and vitamin E can make the muscles more prone to cellular damage.
Individual Variation - in any population some animals are more likely to be affected than others.
Capture myopathy can manifest itself in a number of ways. It can cause collapse and death within minutes of the stress or it can take a few hours or days to show up. In the latter situation the animals may be stiff and sore, reluctant to move, breathing heavily, weak and unable to get up, and depressed. In most cases the animal dies.
Preventing the condition is the only way to effectively control your losses. Some ways to decrease the incidence of capture myopathy on your farm are:
Avoid handling your animals on hot summer days. If you must handle them, work in the cooler parts of the day.
Avoid warm days when the animals still have their winter coats.
Keep the animals as calm as possible. Design the facilities so that stress is kept to a minimum. Work the animals as calmly as possible so that they are not overly frightened. Take your time and don’t rush things.
Familiarize your animals with the handling facilities. Leave the gates open and allow them to investigate on their own time. They will be much less frightened.
Familiarize your animals with humans. Tame them with feeding and by regular contact.
Don’t restrain them any longer than necessary.
Make sure that the nutrition is optimal. Supplement with vitamin E and selenium if you are in a deficient area.
Capture myopathy is very difficult to treat and almost all affected animals die. As we develop better animal handling techniques and our animals become more accustomed to people, this condition is seen less frequently. By using the above tips you should be able to keep the incidence of capture myopathy to a minimum on your farm.