Iodine carry over in dairy cows: effects of levels of diet fortification and milk yield

Abstract

Thirty multiparous lactating cows were divided in three groups based on milk yield: high (H), average (A) and low (L). Within each group, cows were randomly allotted to two levels of iodine inclusions into the diet and respectively: level 1 (1): base diet containing 1.55 mg/kg dry matter, level 2 (2): base diet plus 47.2 mg/d. Potassium iodide was used. Feeds, orts, drinking water and individual milk samples were collected and analysed for the iodine content. The iodine concentration and total excretion in milk were affected by the level of iodine supplementation (P<0.05). No effect on milk iodine concentration could be addressed either to the level of milk yield or to the milk yield x treatment interaction. The total amount of iodine excretion and carry over were affected (P<0.05) by the level of milk yield.