Studies on the binding of selenium by liver homogenates from rats fed diets containing either casein or casein plus linseed oil meal

Dietary effects on selenite toxicity in the chick

The toxicity of Na2SeO3 in diets containing torula (TY) or brewers' yeast (BY) compared to a corn-soy (CS) diet was investigated. Chick mortality caused by feeding 50 or 75 ppm Se as Na2SeO3 was significantly less with TY diets than with either BY or CS diets. The TY diet was also effective in reducing the depressing effect of Se on feed consumption and weight gain. Chicks fed 50 ppm Se in the TY diet accumulated the least amounts of Se in their livers and had only moderate hepatocellular fatty metamorphosis, whereas, those fed the same level of Se in BY diet accumulated the greater levels of Se and showed severe fatty metamorphosis. Partial or total replacement of TY (11%) with BY in the diet significantly increased mortality due to Se toxicity. Some protection against Se toxicity was associated with the ash fraction of TY. This may indicate that the protective effect of TY against Na2SeO3 toxicity is due at least in part to its mineral content.

Fractionation studies on a factor in linseed meal protecting against selenosis in chicks

Growth rate of Single Combe White Leghorn cockerels fed a casein-gelatin-glucose diet was significantly depressed at two weeks when 10 p.p.m. or more selenium was added to the diet. When 20% linseed meal was included in the diet, growth was not reduced with 10 p.p.m. selenium and only slightly reduced with 20 p.p.m. selenium. Including 20% soybean meal failed to modify the toxicity. Levels of 5 and 10% linseed meal were less effective in counteracting selenosis than was 20%. Fractionation studies showed that a protective factor in linseed meal was extracted by methanol and ethanol and was not destroyed by autoclaving. Ashing the ethanol extract destroyed its activity. The factor was readily extracted by chlorform:methanol (2:1) but less effectively by acetone and diethyl ether. Washed chloroform:methanol extract was inactive but the washings contained the factor. Concentrates of the factor were active at less than 1% of the dry matter of the diet. The results of these studies show that linseed meal contains a heat stable, organic, polar factor that modified selenium toxicity in the chick.