The effect of prolonged Kale feeding on the thyroid glands of sheep

Abstract

Four groups of sheep were fed the following rations: Group I Kale ad lib., Group II Kale ad lib.+0·22 kg. blood meal/flaked maize mixture, Group III Kale ad lib.+0·22 kg. blood meal/flaked maize mixture and 10 mg. Kl weekly by mouth, Group IV 0·9 kg. hay+0·22 kg. blood meal/flaked maize mixture. They were fed these rations for 17 weeks when the sheep were killed. The thyroids were removed, weighed and pieces were taken for histological examination. The kale had a goitrogenic effect which was overcome by the iodine supplementation. The group receiving kale showed only a three-fold increase in thyroid weight whereas the group receiving the blood meal/flaked maize mixture in addition to the kale showed a six-fold increase in weight. The mixture had no goitrogenic effect when fed without kale to the control group. The mixture appears to increase the goitrogenicity of the kale. The histology shows considerable hypertrophy of follicular epithelial cells and a diminution in colloid and this accounts for the weight incrase of the glands.