Particularly after a wet season, I hear farmers in the hilly country east of the Hume Highway comment "some of my newborn lambs have an enormous lump under its throat". Invariably, this is relating to goitre.

If you consider the main source of iodine is from sea salt, leached from soils during heavy rainfall, it's not surprising that many of our soils in north-east Victoria are deficient.

Cases of goitre typically occur after three consecutive months of 80mm of rain. Since a reasonably wet winter has been forecast after our effective autumn break, producers with flocks lambing from mid-winter onwards should consider the prevention of goitre in their flocks. Like other essential trace minerals, iodine is only required in small amounts.

The thyroid gland produces hormones, which are essential for life. A lamb or kid with goitre will often be undersized or stillborn, have a reduced wool cover, and be weak and susceptible to cold stress. Goitre in newborn calves is extremely rare.

Property owners who have never seen goitre will often see it after a shift in their enterprise from producing cattle to sheep or goats.

An outbreak of goitre can be challenging to manage since any affected lambs or kids will have a low survival rate, and the deficiency in the ewes or does needs to be corrected quickly before lambing or kidding occurs.

Iodine deficiency is easy to prevent with iodised salt from the third month of the ewes' pregnancy. This can be given in a variety of ways such as iodised salt blocks or potassium iodide drenches.