New Forest Pony

New Test Available: Congenital Myotonia (CM) in the New Forest Pony

Congenital myotonia (CM) is a heritable neuromuscular disorder that affects the New Forest Pony and is characterized by a slow relaxation of skeletal muscles following voluntary contraction. This condition also affects humans and goats (“fainting” goats).

Affected foals are born normal and have well developed musculature soon after birth but begin showing signs of this neuromuscular disorder within the first few months of life. These affected foals are often seen lying down and have difficulty rising to their feet due to muscle stiffness. 

The CM allele is inherited in an autosomal recessive manner, meaning that an animal must inherit two copies of the CM allele to be affected by this neuromuscular disorder. Horses with one copy of the CM allele are carriers and, while they will be normal, they may pass on the CM allele to their offspring. Genetic testing allows owners and breeders to identify affected and carrier individuals and select mating pairs that will not produce affected foals. 

To read more about the test visit