When startled or excited, certain goats exhibit a peculiar reaction where their muscles stiffen, causing them to fall over. This phenomenon, often mistaken for fainting, is a unique characteristic of a specific breed. Unlike a true faint, which involves a loss of consciousness due to reduced blood flow to the brain, these goats remain fully aware of their surroundings throughout the episode. This temporary rigidity is a genetic trait.
Meet the Myotonic Goats
The goats known for this distinctive behavior are Myotonic goats, an American breed with several common names including Tennessee Fainting Goats, Nervous Goats, or Wooden-Leg Goats. They are characterized by a stocky build, dense musculature, and a broad body, often appearing wider than other goat breeds. Their facial features can include prominent eyes in high sockets and a straight or convex profile. Myotonic goats come in various colors and coat lengths, with some individuals growing significant cashmere during colder months. They are generally smaller than standard goat breeds, usually standing between 17 to 25 inches tall and weighing 60 to 174 pounds.
Understanding the Muscle Stiffness
The temporary muscle stiffness in Myotonic goats is caused by a genetic condition called myotonia congenita. This inherited neuromuscular disorder affects the skeletal muscles, which are responsible for voluntary movement. The condition arises from a mutation in the CLCN1 gene, which provides instructions for building chloride channel 1 proteins. These chloride channels play a role in regulating the electrical activity of muscle cells and enabling them to relax after contraction.
When a Myotonic goat is startled or experiences sudden excitement, its muscles receive a signal to contract. However, due to the mutated CLCN1 gene, the chloride channels do not function correctly, leading to an impaired flow of chloride ions. This disruption means the muscle fibers remain electrically excitable and cannot quickly return to a relaxed state after contraction. The delayed relaxation causes the muscles to become rigid and lock up for a short period, typically lasting from 5 to 20 seconds.
Impact on Goat Health and Behavior
Myotonia congenita is generally considered a benign condition that does not cause pain or long-term health issues for Myotonic goats. The muscle contractions during these episodes are similar to isometric exercise, contributing to their notable muscularity. Over time, some older goats learn to adapt, managing to stay upright or brace themselves even when startled, rather than falling over.
Myotonic goats are recognized for their docile and quiet temperament, often being less vocal than other goat breeds. Their calm nature makes them relatively easy to handle and manage. They are also efficient foragers and, due to their temporary stiffness, are less prone to climbing or jumping fences, making them easier to contain within pastures. This breed is valued for its meat production due to its high meat-to-bone ratio and well-developed musculature.