Fainting goat - WikiHQ

thumb|right|300px|A fainting goat kid in the midst of a myotonic "fainting" spell.

The fainting goat or myotonic goat is an American breed of goat. It may also be known as the Tennessee fainting goat, falling goat, stiff-legged goat or nervous goat, or as the Tennessee wooden-leg goat. The fainting goat is characterized by myotonia congenita, a hereditary condition that may cause it to stiffen or fall over when excited or startled. Four goats of this type were first brought to Tennessee in the 1880s.

History

Fainting goats were first brought to Marshall County, Tennessee, in the 1880s. Existing breeds of myotonic goats seem to have originated from a limited number of goats in Tennessee in the 1880s. The mutation in the goat gene that causes this muscle stiffness was discovered in 1996, several years after the equivalent gene had been discovered in humans and mice.

The experiments of Brown and Harvey in 1939 with the myotonic goat made a major contribution to the understanding of the physiological basis of this condition and influenced many other theories of myotonia and its causes.

Characteristics

Myotonic goats vary heavily in their characteristics in comparison to other goat breeds, and they possess certain traits that other goat breeds do not. Congenital myotonia can be inherited as an autosomal dominant trait (with incomplete penetrance) or a recessive trait, resulting in the varying severity of the condition. In affected goats, the CLCN1 gene contains a missense mutation; the amino acid alanine is replaced with a proline residue. This missense mutation occurs in a sequence of seven amino acids that are included in a group of closely related channels including that of humans and rats. It has been shown that the increased muscle excitability is largely accounted for by the lack of chloride permeability in these fibers. These differences help to explain increases in the severity of myotonia in the whole animal that occurs upon decreasing the temperature of the involved muscles. Previous studies have also reported that taurine, an amino sulphonic acid, when given to myotonic patients can reduce the symptoms of the condition. However, it has been shown that it neither antagonizes the condition, nor prevents it. and can range from mild to severe.

Myotonic goats tend to be less preferred for sustainable meat production. Meat production from goats uses maternal breeds that demonstrate high levels of fitness under non-optimal situations. Myotonic goats' maternal fitness cannot be assessed with conventional methods. To estimate their maternal fitness, the health and reproductive traits of 80 myotonic goats were compared to those of Spanish goats, Kiko goats, and Boer goats. The study measured fecal egg count (FEC) and packed cell volume (PCV). Myotonic goats tended to have a lower body mass and a lower FEC, but a greater PCV than Boer goats. Weaning rates, annual kidding rates, doe retention rates and kid crop weaned were similar in all goats except myotonic goats, which had the lowest FEC compared to other breeds. This indicates that myotonic goats are less suited for meat production under non-optimal conditions.

References

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