GROWTH, REPRODUCTION, DIGESTIBILITY, PROTEIN AND VITAMIN A RETENTION OF RATS FED SOLVENT-EXTRACTED RAPESEED MEAL OR SUPPLEMENTAL THIOURACIL

Abstract

Weanling rats were fed 19.4% protein diets containing either 13% soybean meal, soybean meal plus 0.05% thiouracil, or 15% solvent-extracted rapeseed meal to replace the soybean meal at an isonitrogenous level. Dietary rapeseed meal did not influence food intake, reduced rate of gain for 8 to 10 weeks, and resulted in poorer food/gain ratio for female rats for the 20-week period but for male rats for only 2 weeks. Rapeseed meal did not affect energy digestibility but increased protein digestibility and retention. Thiouracil reduced energy and protein digestibility but had no consistent influence on protein retention. Both rapeseed meal and thiouracil-supplemented rats had lower vitamin A fecal losses than soybean meal-supplemented rats.Thyroid hypertrophy occurred after 4 to 6 weeks for rapeseed meal rats and after 2 weeks for thiouracil-supplemented rats. After approximately 8 weeks the thyroid to body weight ratio reached an equilibrium. Liver to body weight ratio was increased for several weeks by feeding rapeseed meal or thiouracil to male rats. There was no close relationship between thyroid hypertrophy and rate of body weight gain, efficiency of food utilization, or energy and protein digestibility.Litter weight at birth averaged only 47 g for litters from females receiving rapeseed meal as compared with 69 g for litters from females receiving soybean meal although numbers of rats per litter were similar.