White muscle disease in sheep and goats
tiff lamb disease - nutritional muscular dystrophy
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 suceptible 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 successfuly 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 intenstine. 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.
References: Sheep & Goat Medicine edited by D.G. Pugh (2002);
Goat Medicine by Mary C. Smith and David M. Sherman (1994); and Sheep Production
Handbook by the American Sheep Industry Association (2002).
Copyright © 2004.
Resources and additional reading
Vitamin
E and Selenium Deficiency - Organic Vet
White
Muscle Disease - Purdue University
White muscle and other Se-responsive diseases of livestock
White muscle disease (vitamin E and/or Se deficiency)
Created or last updated
by Susan Schoenian on
21-Dec-2009
.