Prevention and treatment
Tablelands Telegraph – May 2021
Lucienne Downs – District Veterinarian
Our District Vets have seen many cases of iodine deficiency causing goitre in kids and lambs in 2020-2021. Some adult ewes have also been found to have goitre. Low iodine levels have been found in some flocks tested.
Goitre in newborn lambs and kids occurs when there is iodine deficiency during pregnancy when the demand for iodine in the developing foetus is high in the final trimester of gestation.
In many regions of Australia, the soils are marginal or low in iodine. High autumn rainfall and resulting lush pasture growth will further reduce the availability of iodine making the risk of goitre higher.
Grazing brassica crops or white clover during pregnancy can cause goitre as goitrogens in these plants reduce the availability of iodine.
Overt goitre may be obvious in lambs and kids if it is many times larger than normal. A ratio of thyroid to lamb weight of more than 0.4g/kg indicates an enlarged thyroid.
Iodine deficiency can cause poor conception, abortion, stillbirths and the birth of premature or small and weak lambs or kids. Kids may be born with a sparse hair coat and lambs may be born hairy. Affected neonates have a decreased metabolic rate, impaired lung development and impaired suckling behaviour and have an increased mortality rate from starvation – mismothering and are especially cold susceptible.
Prevention and treatment:
The need for preventative measures will depend partly on the history of the property and herd/flock including a previous diagnosis or suspicion of iodine deficiency, timing of lambing/kidding and seasonal conditions.
As goats have a higher requirement for iodine it has become a standard recommendation that pregnant does grazing in high rainfall areas receive a drench of supplementary iodine once or, in some cases twice, during the last two months of their pregnancy.
Iodine supplementation of ewes depends on the region and seasonal conditions.
Iodised salt licks or iodised salt in the diet will prevent the development of iodine deficiency. Potassium iodide may be given as a drench.
Lambs with goitre can be treated with thyroxine or iodine supplements, however, only slight reductions in the size of the goitre are likely once established.
An overdose of iodine can result in iodine toxicity so correct diagnosis and supplementation is important. Speak to your local private veterinarian or District Veterinarian for advice for your circumstances.
Always report livestock abortions to a vet so that they can investigate to find the cause and rule out zoonotic diseases (those that can cause disease in people) and exotic diseases via lab testing. Testing to show that we are free of exotic diseases supports our livestock markets. It is important to take precautions such as using personal protective equipment (gloves, overalls, boots, masks and googles) and practice scrupulous personal hygiene when handling placentas and aborted livestock materials.