Effects of acute iodine toxicity on reproduction in a dairy herd

Abstract

The feeding of supplemental 12 170 mg/cow/day iodine, (approximately 1000 times the daily requirement) to 60 high producing Guernsey cows for 30 days resulted in 12 abortions within a 68 day period following the initial date of iodine feeding. The 12 cows which aborted had a mean lactation length of 200 days and 87 day gestation length at the time of initial feeding. The annual abortion rate in the herd increased from 3% to 16% following the excessive iodine intake. The majority of the abortions occurred in cows which were in the first trimester of pregnancy when feeding began. The subsequent fertility was normal. The number of days open and services per conception were increased in the 20 open cows which were being bred during the period when the iodine intake was excessive. The maximum iodine intake recommended for lactating dairy cattle is 12 mg/day.