White Muscle Disease (WMD) in Sheep and
Goats
Stiff Lamb Disease
Nutritional Muscular Dystrophy
by
Susan Schoenian
Sheep & Goat Specialist
Western Maryland Research & Education Center
University of Maryland Cooperative Extension
Date created or revised:
23-Oct-2007
What is it?
White muscle disease (WMD) is a degenerative muscle disease found in all
large animals. It is caused by a deficiency of selenium and/or vitamin E.
Generally, it is not known which. Selenium (Se) deficiency is associated
with selenium deficient soils and the inadequate uptake of selenium by
forages grown on these soils. Certain areas of the U.S., including the
Northeast, are considered low in selenium levels. Selenium deficiency
occurs when the soil contains less than 0.5 mg Se/kg of soil and locally
harvested feeds contain less than 0.1 mg Se/kg of feed.
Vitamin E deficiency is
independent of soil type and more closely reflects forage quality.
Grazing animals usually consume adequate amounts of vitamin E. This is
because fresh legumes and pasture are good sources of vitamin E, whereas
silage, oil seeds, root crops, cereal grains, and dry hays tend to be poor
sources of vitamin E. Prolonged storage of feedstuffs results in a
degradation of Vitamin E activity, as much as 50% per month.
In addition to WMD, selenium and vitamin E deficiencies can produce
symptoms of ill thrift and reproductive losses: lower conception rates,
fetal reabsorption, dystocia, retained placenta, reduced milk production,
and reduced semen quality. They can cause poor rate of growth or ill
thrift in young lambs throughout the growing period. Sheep consuming
selenium-deficient diets produce low wool yields and have increased
incidence of periodontal disease. Selenium and vitamin E also play key
roles in the animal’s normal immune response.
Symptoms
All breeds of sheep and goats are susceptible to WMD, and the condition
may develop under extensive or intensive management systems. WMD is most
commonly found in newborns or fast growing animals. Kids are believed to
be more susceptible than lambs, possibly because they have a higher
requirement for selenium. The disease can affect both the skeletal and
cardiac muscles.
When the skeletal muscles
are affected, symptoms vary from mild stiffness to obvious pain upon
walking, to an inability to stand. Lambs/kids may tremble in pain when
held in a standing position. A stiff gait and hunched appearance are
common. Affected lambs/kids may remain bright and have normal appetites,
but eventually they become too weak to nurse. When the problem occurs in
newborns, they are born weak and unable to rise. Sudden exercise may
trigger the condition in older lambs and kids.
When the disease affects
the heart, the animal shows signs similar to pneumonia, including
difficult breathing, a frothy nasal discharge (may be blood stained), and
fever. The heart and respiratory rates are elevated and often irregular.
Skeletal and cardiac muscle disease may occur concurrently.
Selenium deficiency can be
confirmed by measuring selenium levels in whole blood or tissues. A
diseased animal will have less than 0.04 ppm of selenium in its blood.
Breeding ewes require more selenium, and their blood levels should be over
0.5 ppm. At necropsy, the muscles of affected animals appear paler than
normal and may show distinct longitudinal striations or a pronounced
chalky appearance due to abnormal calcium deposition.
Treatment
Treating the heart form of WMD is usually ineffective and those that
survive often do not thrive because of the residual cardiac damage. The
muscle form of the disease can be successfully treated with supplemental
selenium and/or vitamin E. Producers need to follow label directions
carefully when using selenium for treatment. The concentrations of
selenium (per ml) vary greatly with each product, and excessive or
repeated injections can result in selenium toxicity and possibly death.
The commercially available
selenium/vitamin E product's) commonly used in the U.S. do not contain
therapeutic levels of vitamin E. Additional vitamin E may need to be
provided through an injection of vitamin E alone or through oral vitamin E
products. Affected animals usually respond favorably to a single treatment
of vitamin E and/or selenium in 24 hours, though recovery may not be
complete, depending upon the severity of the condition. Animals which do
not respond to treatment may be treated a second time. Treatment should
not exceed two doses.
Prevention
Deficiencies occur when animals are fed poor-quality hay or straw or lack
access to pasture. High concentrations of other minerals (e.g. calcium,
sulfur, copper) and feed contaminants (e.g. nitrate, unsaturated fats,
sulfates) may decrease absorption of selenium in the small intestine.
Diets high in polyunsaturated fatty acids or deficient in Vitamin C and/or
beta-carotene increase vitamin E requirements, whereas adequate dietary
selenium is almost completely protective against vitamin E deficiency.
WMD can be prevented by supplementing the diet of susceptible animals with
selenium and vitamin E. Since it occurs mostly in lambs and kids whose
mothers were fed a selenium-deficient diet, supplementation of pregnant
animals helps reduce disease in newborns. This is because selenium is
transferred from dam to fetus across the placenta and also is present in
the colostrum. While not much Vitamin E is transmitted across the
placenta, colostral levels of Vitamin E increase with ewe/doe
supplementation.
While pasture, hay, grain, and other supplements can be analyzed to
determine the amount of selenium to be added to supplemental feeds, it is
important to note that selenium supplementation is controlled by law. For
sheep, selenium can be supplemented in a complete ration at a level up to
0.3 ppm, in a feed supplement so that the intake of selenium does not
exceed 0.7 mg per head per day, and in salt/mineral mixes at 90 ppm as
long as total daily consumption does not exceed 0.7 mg/head/day. Selenium
supplementation of feed has not been approved specifically for goats.
Injectable selenium compounds are available to prevent WMD in at
risk-animals; however, injections are a poor alternative compared to
routinely providing adequate selenium and vitamin E in the diet. Ideally,
the total diet for sheep and/or goats should contain 0.10 to 0.30 ppm of
selenium.