An iodine deficiency can be one reason for stillborn or less vigorous calves at birth, according to Vicki Fisher, vet at Farm First Vets, Abergavenny.
Deficiency affects fertility and can manifest in stillborn or weak calves, which do not suckle and are slow to get up.
Miss Fisher says: “We are becoming increasingly aware of the importance of iodine in our practice and it is making its way up the list of things to consider when it comes to neonatal calf health. Iodine availability in the soil varies geographically and in our area of the country, many farms are deficient.”
Iodine is involved in one of the chemical reactions in the thyroid, responsible for regulating metabolism and essential for thyroid function, she explains.
Miss Fisher says low iodine can also equate to fertility issues with cows not getting in-calf.
“There are few outward clinical signs shown by cattle with this deficiency but sometimes calves subjected to low iodine via their mother can be born with an amount of hair loss and some papers say calves may have fluid under the skin, but I am yet to see this myself. However, on post-mortem, affected calves may show an enlarged thyroid gland.
“Blood tests can be useful in identifying iodine deficiency but they need interpreting,” she says.
Deficiencies can often be a result of the soil and depend on the level of fertiliser applied. The mineral is also thought to be linked with selenium, so if iodine levels are low, selenium might be too.
Some pre-mixed concentrates include iodine, but there is a cap on the level included by mills and sometimes this may still not be sufficient for animals, explains Miss Fisher.
Goitrogens are substances which can bind iodine and block its uptake and therefore disrupt thyroid function. They are found in brassicas and legumes and can further worsen the deficiency. Some processed feeds, such as rapeseed meal have however had some of the goitrogens removed.
Miss Fisher says: “Iodine deficiency is more common in grass-based systems, being more reliant on the soils and not benefiting from the minerals found in fortified concentrates, but it can be seen in all sorts of systems.
“Do not go adding iodine without being sure it is the cause of your problem. Unnecessary supplementation of iodine can lead to a form of toxicity in calves which results in poor absorption of antibodies from colostrum, which is vital for the calf to develop a strong immune system.
“Cattle are quick to respond to an increase of iodine their bodies. I find some brands of high iodine bolus are the best option to treat the animal and, although labour intensive when administering, they can last six months.
“Drenches can also be made up on-farm with the advice of a vet or an application of an iodine solution to the coat, which may be absorbed by the skin or licked off by others. Iodine can be added to water supplies if it is the only available water but too much can cause a taint to water so again be sure to use the correct dilution.
“There are many causes of poor calf vigour and stillbirths, so if you are experiencing these problems then it is vital to speak to your vet about the possibility of it being due to an iodine deficiency.”