Abstract

The aim of this work was to determine the size of the thyroid gland and the weight gain of calves born from dairy cows supplemented with iodine (I) during prepartum. Fourteen Holstein-Friesian calves were used. They were born from 7 cows supplemented with a single dose of I (I-S, 1.6 g/cow, Lipiodol®) at seven month of pregnancy and 7 non supplemented cows (I-C). Cows grazed a low I content pasture (0.19ppm) until calving. The thyroid gland of the calves was examined by ultrasonography at days 36 and 128 (± 7.5) of age. Calves were weighted at 26 and 110 (± 7.5) days of age and the daily weight gain (DWG) was determined. The thickness of the isthmus of the thyroid at 36 days of age were similar between groups (P > 0.05). A reduction in thickness was observed in both groups at 128 days, more pronounced in I-C group (P < 0.05). The left lobule was larger at 36 days of age in the I-C group than in I-S group (P < 0.05). An increase in size of the left lobule was found in both groups after 128 days (P < 0.05). The size of the right lobule was similar for both groups (P > 0.05) in both periods. Calves of both groups had a similar weight and DWG at 36 and 128 days of age. It was concluded that a single supplementation with I for pregnant dairy cows grazing a low iodine content pasture induced a reduction in the growth of the left lobule of the thyroid in their offspring without affecting the growth of the calves.