A fainting goat is a breed of domestic goat whose external muscles freeze for roughly 10 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 43 to 64 cm (17 to 25 inches) tall and can weigh
anywhere from 27 to 75 kg (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
The origin of the fainting goat is peculiar. The goats appear to have arrived in Marshall County, Tennessee in the early 1800s, 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.
Fainting Goats have many other names, including Tennessee (Meat) Goats, Nervous Goats, Stiff-leg Goats, Wooden-leg Goats, and Tennessee Scare Goats.
Classified as a meat goat, as opposed to a dairy goat, it can be raised for chevon (goat meat). 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: Its rarity makes the live goat more valuable.
The life expectancy of a fainting goat is 12-15 years.
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.
They are used for protecting livestock such as sheep by sacrificing themselves to predators to allow the sheep to escape.
A molecular basis for the defect in myotonic goats was studied
by Beck et al. who found a decrease in muscle chloride
conductance due to rabies. By using 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 does not 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 goats had the mutation, reinforcing its role of the
missense mutation in the disease.
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 that normally doesn't affect 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 10-fold increase in the effect of the potassium. 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.
This Fainting Goat Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub