The Effect of Zearalenone on Growth Rate, Organ Weight and Muscle Fibre Composition in Growing Rats

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Abstract
The effect of prolonged zearalenone administration to growing rats on body and organ weight as well as on muscle fiber composition was studied. Two muscles, M. [musculus] longissimus dorsi and M. vastus lateralis, were selected for fiber analyses, and the different fiber types were identified by histochemical staining. Zearalenone caused retarded growth and reduced carcass weight in both sexes. With low daily doses, female growth was retarded more than was male growth; with higher doses the effect was the opposite. The most evident effects of zearalenone treatment on organ weight were enlargement of the liver in both sexes and of adrenal glands and the spleen in males. No effects were found on heart, kidney, testes or uterus. No significant changes in fiber number or diameter occurred in male rats after prolonged zearalenone feeding. In female rats there was a 40% decrease in the number of .alpha.R fibers in vastus and a corresponding increase of .alpha.W fibers. Simultaneously, the .alpha.R fiber size increased 25%. No significant changes could be found in the activity of 2 enzymes in vastus, cytochrome oxidase and lactate dehydrogenase due to zearalenone treatment.