Out wintering heifers on kale face the potential risk of iodine deficiency when an increasing number of producers are opting to reduce costs over the winter on this popular brassica.

Additional supplementation with minerals is crucial to maintain key targets for growth, performance, and fertility in replacement dairy heifers, especially when grazing kale.

This is due to it containing a high level of goitrogens, which negatively impact the bioavailability of iodine and can subsequently induce a host of problems.

Goitrogens found in kale work antagonistically with iodine, influencing the metabolism of the mineral in the animal.

Kale contains a type of goitrogen, thiocyanate, which originates in glucosinolates found in plant matter. This interferes with the uptake of iodine into the thyroid when consumed. The problem can be further compounded in areas with acidic soils.

Soil pH, which varies regionally, can also affect the uptake of iodine into the plant tissue itself. This, combined with a high level of goitrogens, significantly reduces the availability of iodine in kale-based diets.

If cattle become deficient in iodine, their health, growth and performance can be compromised, and lethargy and poor eating habits may be noticed.

Hormone production can also be affected with an iodine deficiency impacting thyroid function. Fertility can be significantly affected by reduced iodine availability during the winter because a hormone imbalance can cause stillbirths and pre-natal mortality.

Bolusing out wintered heifers is a good way to supplement minerals as it can provide a sustained supply of micronutrients for six to eight months