We evaluated the potential for gossypol intoxication and resulting effects of feeding large amounts of cottonseed meal to dairy cows in early lactation. Twenty-four Holstein cows were grouped by age, prior production, and days postpartum and randomly assigned to one of three diets. After 14-day standardization cows individually were fed a blended corn-corn silage ration supplemented with screw-pressed cottonseed meal, direct solvent extracted cottonseed meal, or soybean meal during a 14-wk comparison. Packed cell volume, copper in plasma, activities of transaminases, and gross composition of milk were not affected by ration. Hemoglobin was depressed, and total protein of plasma was elevated by the 9th wk in cows fed the solvent meal. Erythrocyte fragility was detected in those cows by the 7th wk and appeared later in cows fed the pressed meal. Gossypol was identified and quantitated in plasma and liver but was not detected in erythrocytes or milk from cows fed cottonseed meal. Elevated ambient temperatures precipitated increased respiration rates in the cows fed solvent meal. Physiological changes and gossypol in tissues of cows suggest that intoxication is possible in mature ruminants consuming cottonseed meal containing high free gossypol.

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The Amerlex Free Thyroxin (T4) Radioimmunoassay Kit (Amersham International Ltd.) is a new direct equilibrium radioimmunoassay for free T4 based on an antiserum with very high affinity for T4, and a unique 125I-labeled T4 analog as tracer. It is a very simple single-tube radioimmunoassay, making use of Amerlex particles to separate antibody-bound from free species. Interassay precision (CV) is 3.7% at 13 pmol/L and 2.3% at 30 pmol/L; within-assay precision is 4.2% at 21 pmol/L. The reference interval is 11-22 pmol/L. The assay did not misclassify any patients tested who had untreated myxedema or untreated thyrotoxicosis. The free T4 assay excelled both the free T4 index and the T4/T4-binding globulin ratio in correcting for increased thyroxin-binding globulin from pregnancy, and it was better than the index but not better than the ratio in correcting for increased thyroxin-binding globulin in users of oral contraceptives.

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