Effect of whole and fractionated dietary alfalfa meal on zearalenone toxicosis and metabolism in rats and swine

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Abstract
Experiments were conducted to determine the mechanism by which dietary alfalfa can protect against zearalenone toxicosis. Female weanling rats were fed semipurified diets containing whole alfalfa meal, fractionated alfalfa meal (fiber, solvent extract, and water extract), and purified components of alfalfa (coumestrol, saponin, lignin, coumestrol + lignin, and saponin + lignin) with and without 250 mg zearalenone/kg of diet. All ingredients were provided for 2 weeks at levels corresponding to those found in diets containing 15 and 25% alfalfa. Yorkshire gilts were fed 15 and 25% alfalfa meal with and without 10 mg zearalenone/kg of diet for 4 weeks. The feeding of zearalenone to rats reduced growth and food consumption but this was overcome by 25% alfalfa. Zearalenone also increased the activity of hepatic 3α-hydroxysteroid dehydrogenase (3α-HSD), the enzyme believed to metabolize zearalenone to α- and β-zearalenols. Dietary alfalfa did not overcome this effect. Alfalfa fiber was the only fraction to partially overcome the growth-depressing effects of zearalenone while the other fractions had no beneficial effects and 3α-HSD was not affected by diet. None of the purified components affected growth parameters or 3α-HSD. The enzyme was also not affected by zearalenone or alfalfa in swine diets. Coumestrol, α-zearalenone, and β-zearalenone were shown to be competitive inhibitors of 3α-HSD in rat liver. It was concluded that the fiber fraction of alfalfa protects against zearalenone toxicity, and that this effect is not dependent on coumestrol or saponin and is not likely mediated through 3α-HSD.