Iodine is an essential trace element for livestock health. Although iodine deficiency is less common than copper, selenium, or magnesium deficiencies, it can still occur in certain areas and under specific feeding conditions.

Where Iodine Deficiency Occurs

In New Zealand, iodine deficiency is occasionally seen in livestock grazing on iodine-deficient soils—particularly in some inland regions and alluvial plains. Feeding brassicas and some types of clover can also trigger deficiency. These plants contain goitrogens, compounds that interfere with the production of thyroid hormones.

Signs of Iodine Deficiency in Livestock

The most recognisable symptom is goitre, which presents as a swelling of the thyroid glands just below the throat. Goats are particularly susceptible, but deficiency may also affect lambs, fawns, calves, and foals.

Other signs include:

• Poor survival rates in newborn animals

• Reduced milk production in cows

• Lower wool production in sheep

• Reduced fertility in ewes and cows

Diagnosis and Treatment

Diagnosis is usually based on clinical signs. If iodine deficiency is suspected:

• Pregnant cows, ewes, and young animals can be dosed with potassium iodide every 3 to 6 months

• A long-acting iodine injection may be used in more severe or high-risk cases

• In lower-risk areas, iodised salt licks are often sufficient

If you suspect your property may be iodine-deficient, consult your veterinarian to determine appropriate supplementation.