Causative Agent:
Muscle problems associated with this disease are caused by low dietary levels of selenium and vitamin E. Certain areas of the United States (northeast, southeast, and northwest) are considered low in selenium levels. Therefore, animals that reside in these areas are at a greater risk for white muscle disease. This disease is found mostly in young, fast growing sheep or goats and is most commonly caused by low levels of selenium in the mothers’ body during gestation.Clinical Signs:
It is important to realize that this disease can cause problems in the heart and not just the skeletal muscles. When the heart is affected, the animal shows signs similar to pneumonia. These include difficulty breathing, a frothy nasal discharge (may be blood stained), and fever. The heart and respiratory rates are elevated and often irregular.When the muscles of the body are affected, the animal may be weak or stiff depending on the stage of the disease. At first the animal is usually weak and unable to rise. With time, the animal may become stiff, with the legs swollen and painful. When the problem occurs in newborns, they are born weak and unable to rise.
Diagnosis:
An initial diagnosis can be made based on physical exam and past history. This is supported by measuring selenium and creatine phosphokinase (CPK) levels in the blood. A diseased animal will have selenium levels of less than 0.04 parts per million (ppm) and CPK levels in the thousands. These values can vary greatly depending on the laboratory used to test the blood sample. Both forms of this disease can be diagnosed at necropsy.Treatment/Prevention:
When the animal is experiencing heart problems, treatment is usually ineffective. For treating the muscle form of the disease, supplemental selenium and vitamin E are required. It is recommended that 2.5 mg of selenium per 100 lbs. of body weight be given to adult sheep and goats. Lambs and kids should be given 1 mg minimum. Most selenium products come combined with vitamin E; however, the levels of vitamin E in these products are usually too low. It is often necessary to give additional vitamin E. Pay particular attention to the concentrations of selenium per mL, since they vary greatly in each product. Also, keep in mind that excessive levels of selenium will result in selenium toxicity.Supplemental sources of selenium can be provided in an oral or injectable form. The injectable forms should be given at label doses on a monthly basis. Selenium as a supplement can only be fed up to 0.7 mg/head/day according to United States’ regulations. Ideally, the total diet should contain about 0.1-0.3 ppm of selenium. To prevent toxicity, it is recommended that periodical blood testing be performed to monitor and regulate selenium replacement.