Nutritional Muscular Dystrophy (Nutritional Myopathy or White Muscle Disease) is a disease caused by a deficiency of
selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
and
vitamin E
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vi ...
in dietary intake.
Soils that contains low levels of selenium produce forages and grains that are deficient in selenium. Similarly, if the forage is of low quality or is not stored properly it may be deficient in vitamin E.
If an animal consumes this type of diet without additional supplementation they become susceptible to this disease.
This condition often affects young
ruminant
Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...
s, such as calves and lambs.
Selenium and vitamin E are
antioxidants. Therefore, deficiencies of these
nutrients lead to oxidative damage to cells within the body. The muscle cells are the most vulnerable to damage in
livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animal ...
species.
Clinical symptoms
The oxidative damage causes degeneration of muscles, in particular those within the skeletal and cardiac systems. If the cardiac muscles are impaired the animal may exhibit signs of
respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gre ...
distress.
While deterioration of skeletal muscles results in stiffness, weakness, and recumbency.
Treatment & Prevention
If the diet is deficient supplement with selenium and/or vitamin E. Injections can be given to treat the condition or as a preventative measure.
Horses
In
equids
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus'', ...
, it is most common in the first twelve months of life. Neonatal foals born to dams that are selenium-deficient often develop the condition. There are two forms: peracute, and subacute. The peracute form is characterized by recumbency,
tachypnea
Tachypnea, also spelt tachypnoea, is a respiratory rate greater than normal, resulting in abnormally rapid and shallow breathing.
In adult humans at rest, any respiratory rate of 1220 per minute is considered clinically normal, with tachypnea b ...
,
dyspnea
Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...
,
myalgia, cardiac arrhythmias, and rapid death.
The subacute form causes weakness,
fasciculations, cramping, and stiffness of muscles, which can lead to recumbency, as well as a stilted gait,
dysphagia
Dysphagia is difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right.
It may be a sensation that suggests difficulty in the passage of solids or liq ...
,
ptyalism
Hypersalivation, or ptyalism, also known as sialorrhea or hypersialosis is the excessive production of saliva. It has also been defined as increased amount of saliva in the mouth, which may also be caused by decreased clearance of saliva.Medscape ...
, and a weak suckle.
It may be treated with selenium supplementation, but there is a 30–45% mortality rate. Other
sequelae include aspiration pneumonia, failure of passive transfer, and stunting of growth.
Clinical laboratory changes include evidence of
rhabdomyolysis (elevated CK and AST,
myoglobinuria
Myoglobinuria is the presence of myoglobin in the urine, which usually results from rhabdomyolysis or muscle injury. Myoglobin is present in muscle cells as a reserve of oxygen.
Signs and symptoms
Signs and symptoms of myoglobinuria are us ...
) and low blood selenium levels. On necropsy, muscles are pale with areas of
necrosis and
edema evidenced as white streaks.
Horses may also develop a more chronic delayed form of the disease called Neuroaxonal Dystrophy (NAD) or Equine Degenerative Myeloencephalopathy (EDM). EDM is a more severe form of NAD. The diseases are characterized by the damage and degeneration of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
. This disease process is heritable in certain breed bloodlines, such as
Quarter Horse
The American Quarter Horse, or Quarter Horse, is an American breed of horse that excels at sprinting short distances. Its name is derived from its ability to outrun other horse breeds in races of a quarter mile or less; some have been clocked at ...
,
Appaloosa
The Appaloosa is an American horse breed best known for its colorful spotted coat pattern. There is a wide range of body types within the breed, stemming from the influence of multiple breeds of horses throughout its history. Each horse's colo ...
,
Morgan,
Lusitano
The Lusitano, also known as the Pure Blood Lusitano or PSL (''Puro Sangue Lusitano''), is a Portuguese horse breed. Horses were known to be present on the Iberian Peninsula as far back as 20,000 BC, and by 800 BC the region was renowned fo ...
, and
Arabian. It is hypothesized that horses develop this disease continuum because they have a defect in the uptake or utilization of Vitamin E and therefore have a higher baseline requirement.
Sheep (Stiff Lamb Disease)
In lambs, the disease typically occurs between 3 and 8 weeks of age, but may occur in older lambs as well.
Progressive paralysis occurs, which is evident through the following symptoms: arched back, difficulty moving and an open shouldered stance. Cardiac failure may occur in two forms: sudden heart failure or gradual cardiac failure characterized by lung anemia that causes death due to suffocation.
Ewes may be given an injection of vitamin E/selenium prior to lambing to prevent deficiencies in lambs. In areas, such as Ontario, where lambs are highly susceptible to the condition, management practices should include vitamin E/selenium injections.
Cattle
In dairy breeds, the disease may occur in calves between birth and 4 months of age. In rustic breeds or beef cattle, heifers and young steers up to 12 months of age can be affected. In calves, muscles in upper portion of the front legs and the hind legs are degraded, causing the animal to have a stiff gait and it may have difficulty standing. The disease may also present in the form of respiratory distress.
Gallery
File:Blankès tchås åmaye1.jpg, in a heifer
File:Blankès tchås åmaye2.jpg, same animal
File:Blankès tchås agnea1.jpg, in a lamb
File:Roedeur agnea1.jpg, other lamb
External links
Description of the disease in Merck Veterinary Manual{{Clear
References
Sheep and goat diseases
Bovine diseases
Horse diseases