Complex sentence: The only known genetic disorder found in the breed is congenital myotonia, a hereditary muscle disorder, which was identified in 2009 in a New Forest pony foal by researchers in the Netherlands, the first time the condition had been identified in equines.
Split into simpler sentences: The only known genetic disorder found in the breed is congenital myotonia, a hereditary muscle disorder. It was identified in 2009 in a New Forest pony foal by researchers in the Netherlands, the first time the condition had been identified in equines.