Fainting goat
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A fainting goat is a breed of domestic goat whose external muscles freeze for roughly ten seconds when the goat is startled. Though painless, this generally results in the animal collapsing on its side. The characteristic is caused by a hereditary genetic disorder called myotonia congenita. Older goats sometimes learn to lean against something to prevent their falling over, and often they continue to run about in an awkward, stiff-legged shuffle.
Slightly smaller than standard breeds of goat, fainting goats are generally 17 to 25 inches tall and can weigh anywhere from 50 to 165 pounds. They have large, prominent eyes in high sockets, and exist in as many colors as standard breeds do. Hair can be short or long, with certain individuals producing a great deal of cashmere during colder months. There appears to be no angora strain of the fainting goat.
The origin of the fainting goat is peculiar. The goats appear to have arrived in Marshall County, Tennessee in the early 1800's, courtesy of a reclusive and unnamed farm worker who was most likely from Nova Scotia. Before he left the area, he sold his goats - three does and a buck - to Dr. H.H. Mayberry, who bred them.
Other names include: Tennessee (meat) Goats, Nervous Goats, Stiff-leg Goats, Wooden-leg Goats, and Tennessee Scare Goats.
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[edit] Uses for the Fainting Goat
Classified as a meat goat, as opposed to a dairy goat, it can be raised for chevon (goat meat). However, this breed is listed as threatened by the American Livestock Breeds Conservancy so the Fainting goat is not used as often for chevon as other meat goat breeds as its rarity makes the live goat more valuable.[1] Chevon in general is a popular dish in Middle Eastern and Hispanic cuisine, and combined with proper raising and processing requirements, it can be Halal or Kosher.
The Fainting goat is smaller and somewhat easier to care for and maintain than larger meat goat breeds which makes the Fainting goat desirable for smaller farms. Goats in general prefer leafy or woody plants to grasses and therefore make effective weed and brush control for pasture used in rotation by grass grazing animals such as horses. They can also be used to reclaim overgrown fields.
The Fainting goat may also be raised as a pet or show animal as they can be friendly, intelligent, easy to keep, and amusing.
[edit] Molecular basis for myotonia in the goats
A molecular basis for the defect in myotonic goats was studied by Beck et al. who found a decrease in muscle chloride conductance. By utilizing single-strand conformational analysis they found that there were two mutations in the gene that encodes the skeletal muscle chloride channel (ClC-1), one silent mutation which doesn't call for another amino acid and then a missense mutation that calls a proline instead of an alanine. The mutation created a new MboII restriction site, so they performed an allele-specific assay and found that all the myotonic sheep had the mutation, reinforcing its role of the missense mutation in the disease.[2]
Physiologically, what is happening in these goats is the inability of chloride ions to act as a buffer to the action potentials as it does in normal animals. Chloride is a negative ion found on the outside of cells in a much higher concentration than on the inside, with an equilibrium potential close to, or more negative, than the resting potential to the cell. Normally, if there is a slight depolarization the influx of chloride will counteract it acting as a buffer. It can be assumed then, with a lower permeability to chloride it would take less of a depolarization to cause an action potential, increasing the chance for erratic action potentials. After an action potential there is a small rise in the extracellular potassium levels which normally doesn't effect the membrane potential much since it can be buffered by the influx of the chloride ion. With myotonia the chloride ion cannot buffer the increase in extracellular potassium which causes a ten fold increase in the effect of the potassium, and if enough of these depolarizations happen they can reach the threshold and cause spontaneous contractions. Additionally, when the goats are startled there is a decrease in the threshold for an action potential due to their increased arousal. It is easy to understand then, how when they attempt to run away from someone scaring them their lack of buffering capability and their high arousal level can cause them to go into a sustained contraction.
[edit] Trivia
- Fainting Goats are mentioned in the movie Addicted to Love.
[edit] References
- ^ American Livestock Breeds Conservancy Watchlist (2006-04-01). Retrieved on 2006-07-11.
- ^ Beck CL, Fahlke C, George AL Jr. 1996. Molecular basis for decreased muscle chloride conductance in the myotonic goat. Proc Natl Acad Sci U S A. 93(20):11248-52
