Effects of Rapeseed Meal on Growth and Thyroid Function of Broiler Chicks

Abstract

Effects of rapeseed meal on growth and thyroid function of broiler chicks were investigated using three types of rapeseed meal, B. campestris, B. napus and B. napus cv. Bronowski. Goitrin and isothiocyanate contents were 0.18 and 0.04% in B. napus cv. Bronowski (RSM-B), 0.28 and 0.18% in B. campestris (RSM-C), and 0.89 and 0.27% in B. napus (RSM-N), respectively. Each RSM was included at the 10% level, and diets were maintained isocaloric and isonitrogenous by altering the levels of soybean meal and yellow grease. The results obtained were summarized as follows:1) Body weight at 4 and 8 weeks of age and feed conversions in chicks fed rapeseed meal were almost equal to those in the control chicks fed soybean meal.2) Thyroid weight of chicks fed rapeseed meal was 1.3 to 3.0 times larger than that of the control chicks. Enlargement of thyroid in chicks fed RSM-N, which contained 0.89% goitrin, was particularly noteworthy.3) Thyroidal uptake of 131I (24 hours) of rapeseed meal-fed chicks was elevated 1.1 to 2.3 times that of the control group. Thyroidal uptake of 131I per 100mg of the thyroid gland, however, was not affected by rapeseed meal feeding.4) Plasma PB 131I, which reflects circulating level of thyroid hormone, seemed to be not or to be very slightly depressed by rapeseed meal feeding.5) Percentage of 131I-iodothyronines in the thyroid lobes was slightly decreased by feeding of rapeseed meal. However, the content of PAS-stainable (thyroglobulin) in the follicles of the thyroid lobes of chicks fed rapeseed meal was similar to that of the control chicks.6) It was concluded in this experiment that thyroid function in chicks fed rapeseed meal was kept fairly good, despite of the enlargement of thyroid gland.