Encephalomalacia antioxidants

In growing chicks, a deficiency can result in (i) encephalomalacia or crazy chick disease (ii) exudative diathesis, an oedema caused by excessive capillary permeability or (iii) muscular dystrophy. Encephalomalacia occurs when the diet contains unsaturated fats that are susceptible to rancidity. Some antioxidants, in addition to vitamin E, are also effective against encephalomalacia. Exudative diathesis is prevented by dietary selenium, and muscular dystrophy is a complex disease influenced by vitamin E, selenium, and the... 

Characteristic lesions of vitamin E deficiency in animals include necrotizing myopathy (inaccurately referred to as nutritional muscular dystrophy), exudative diathesis, nutritional encephalomalacia, irreversible degeneration of testicular tissue, fetal death and resorption, hepatic necrosis, and anemia. Several of these conditions are directly related to peroxidation of unsaturated lipids in the absence of vitamin E, and others can be prevented by synthetic antioxidants or vitamin E. 

At least one vitamin E deficiency sign is known to occur only when a certain class of polyunsaturated fatty acids is furnished in the diet. For instance, encephalomalacia in chicks appears when the diet contains linoleic or arachidonic acid, but not when the diet is fat free or contains linolenic acid. It is possible that encephalomalacia is due to the lack of an antioxidant effect, but attempts to demonstrate autoxidation products in the affected tissue have not been successful. 

Although some similarities are observed in the tissues of chicks suffering from these diseases, it appears that no common metabolic defect can be held responsible for all three conditions, since various specific dietary changes unrelated to the vitamin E content of the diet can completely prevent one of the diseases without having any effect upon the other two. The most important of these are the prevention of encephalomalacia with synthetic antioxidants, the effectiveness of inorganic selenium in prevention of exudative diathesis, and the role of cystine in preventing muscular dystrophy. 

Vitamin E has been shown over the past forty years to be important in the nutrition of poultry in health and disease, not only for normal reproduction but also (1) as nature s most effective antioxidant for prevention of encephalomalacia, (2) in a specific role, interrelated with the action of selenium, for prevention of exudative diathesis, and (3) in another role, interrelated with both selenium and cystine, for prevention of nutritional muscular dystrophy. 

These results suggest that the presence in the diet of unsaturated fats increase tocopherol requirements to 10 to 100 times the amounts required in their absence. In the prevention of encephalomalacia in chicks it appears that the role of tocopherol is to act as an antioxidant specifically related to linoleic acid metabolism (Scott, 1962). Whether such specificity of action can explain the results obtained with ruminants seems doubtful, in view of the low linoleic acid content of highly unsaturated fraction of cod liver oil. 

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