Goitrogenic Effects of a Corn Silage-Soybean Meal Supplemented Ration

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Abstract
A group of seven cows not receiving supplemental iodine bore calves with en- larged thyroid glands, consumed less feed, produced less milk with a lower milk fat content, and lost less weight during early lactation than another seven cows receiving supplemental iodine. All cows were fed corn silage as the only forage and a con- centrate mix of corn, barley, soybean meal and minerals. In a second trial 16 cows were fed corn silage as the only forage. Half received soybean meal as a source of protein and the others received cottonseed meal and urea. Cows receiving the soybean meal produced calves with larger thyroid glands; however, milk production was not evaluated due to the removal of cows from the experiment. The goitrogenic effect of a corn silage-soy- bean meal ration appears due to soybean meal.