White Muscle Disease
White muscle disease is also known as nutritional myopathy of calves. It is normally is seen in young calves and is associated with deficiencies of selenium or vitamin E, or both.
There are two forms of white muscle disease; a congenital form that affects the cardiac muscle, and a delayed form that is associated with either cardiac or skeletal muscle.
Calves affected by the congenital form of white muscle disease usually die within 2-3 days of birth due to cardiac muscle degeneration.
On examination post death, the heart will show white, chalky subendochondral plaques that are most noticeable in the left ventricle. The result is damage to cardiac muscle cells and Purkinje fibers.
Cattle affected by the delayed form or white muscle disease may exhibit signs ranging from general unthrift and stiffness, to walking with an arched back and spending more time recumbent, depending on the level of selenium in the diet.
Often, the delayed form is brought on by vigorous exercise but if chronically affected, cattle can display splayed toes and a relaxation to the shoulder girdle. If a calf is affected severely it may die of starvation due to an inability to nurse properly due to weakness. The skeletal muscle lesions associated with the delayed from of white muscle disease are usually bilaterally symmetrical and can affect one or more muscle groups. The muscle will have white striations and feel dry and chalky due to abnormal calcium deposits.
Cattle affected by white muscle disease have been treated with sodium selenite and vitamin E in sterile emulsion. This can be administered SC or IM, at 1 mg selenium and 50 mg (68 IU) of vitamin E per 18 kg (40 lb) body wt.
If necessary, the treatment may be repeated two weeks later, but no more than four doses total should be given. In calves affected with simple vitamin E deficiency, treatment with dietary supplementation using ?-tocopherol or substances rich in vitamin E can be used. Calves have been cured using 600-mg of alpha-tocopherol initially; followed by daily doses of 200-mg. Any polyunsaturated fats should be removed from the diet as these may be causing the vitamin E deficiency.
To prevent white muscle disease within four weeks after birth, cows are given 15 mg of selenium, usually as sodium selenite four weeks before calving.
To prevent the delayed type, calves are given 5 mg of selenium at two to four weeks of age and twice more at monthly intervals. A selenium and vitamin E mixture is advocated in some areas. Other procedures for selenium supplementation include administration of intraruminal selenium pellets, use of selenium-fortified salt or mineral mixtures, SC implantation of selenium pellets, or soil application of selenium at 4 g/acre (10 g/hectare) in fertiliser.
Adding selenium to feed for breeding animals or their young is useful in areas of known deficiency. The recommended supplemental level is 0.3 ppm selenium, calculated on the basis of total dry-matter intake. It is added as sodium selenite, which contains 45.65 per cent selenium. Because of the minute quantities involved and the toxicity of excess intake, premixing and thorough subsequent mixing is necessary. In some countries, including the USA, addition of selenium to feeds is controlled by law, and appropriate authorities should be consulted; in all areas, caution in the use of selenium is indicated.
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