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Goiters are lumps on the throat or neck. They range from the size of a marble to huge masses and are caused by the thyroid gland growing larger than normal. They occur in cattle as well as in many other animals, birds, fish and humans. More than 90 percent of goiters in all species are caused by iodine deficiency. In cattle, goiters are seen more frequently in newborn calves than in adult animals.
Iodine is essential for the production of a hormone called thyroxin, which regulates metabolic rate. Pregnant cows need iodine to ensure their calves develop normally. Iodine deficiency leads to weak and even hairless calves, and calves born with goiters. In adult cattle, the deficiency can cause goiters, reduce fertility and limit milk production. A cow's requirement for iodine is 0.5 parts per million of total diet dry matter, which can be supplied in salt licks using iodized salt.
Soils with sandy texture tend to be lower in iodine than clay-textured soils. Cattle grazing on sandy soils are more prone to goiter than others. Sandy soils are often associated with river systems; in the United States, the Great Lakes region, the Midwest and the intermountain regions are low in iodine. In Britain, the English Midlands are goiter prone; in Australia the areas associated with the major river systems are.
When pasture is growing fast in spring and after good rains, cattle are likely to eat less surface soil. Normally they ingest a small amount of soil while grazing, and this acts as a mineral supplement that usually will contain some iodine. Stocking at a higher rate when pasture is growing fast can reduce the likelihood of goiter. Place a trace element block near the cattle’s water source.
Some crops, particularly brassica crops, contain compounds that suppress the production of thyroxin and interfere with the amount of iodine available to the body. Do not allow pregnant cattle to graze on turnips, rape, cabbage, cauliflower, broccoli, soybeans or spinach crops for prolonged periods. You can treat goiter with iodine tinctures, but prevention is better.