Muscular Disorders Affecting Large Animals

Disorder Type

Definition

Examples

Species Affected

Muscular defects

Defects in the formation and disposition of muscle not associated with a lesion in neuronal tissue

Myofibrillar hypoplasia (splay leg)

Pigs

Muscular hyperplasia (double muscling)

Cattle, sheep

Muscular steatosis

Cattle, sheep, pigs

Inherited and congenital myopathies

Genetic muscle disorders that are present at birth, although onset may be delayed

Myopathy of the diaphragmatic muscle

Cattle

Muscular dystrophy of Merino sheep

Sheep

Myotonia

Temporary inability of skeletal muscle fibers to relax, resulting in muscle tension

Myotonia of the goat (“fainting goats”)

Goats

Hyperkalemic periodic paralysis 

Horses

Myotonic dystrophy-like disorder

Horses

Spastic paresis of cattle

Cattle

Metabolic myopathies

Abnormal skeletal metabolism leading to neuromuscular dysfunction

Equine polysaccharide storage myopathy

Horses

Glycogen branching enzyme deficiency 

Horses

Myophosphorylase deficiency (glycogen storage disease)

Horses, cattle, sheep

Malignant hyperthermia

Results in sudden increase in myoplasmic calcium concentration, prolonged contraction, and life-threatening hyperthermia

Malignant hyperthermia (porcine stress syndrome)

Pigs

Malignant hyperthermia-like syndrome

Anesthetized horses

Primary CNS conditions

Neuroectodermal defect leading to denervation of muscle 

Arthrogryposis 

Horses, cattle, sheep, pigs