Stephanie Patel BVetMed MRCVS Molecare Farm Vets
The issue of iodine deficiency can be identified as far back as the 18th century in England, when the deficiency was common amongst the human population, with areas such as the South West appearing to be more pre-disposed to the problem. It wasn’t until the early 1900’s, and in particular when dairy farmers in the region began to supplement their cows with iodine, that a reduction in the deficiency was also seen in the human population. Whilst the deficiency in humans is now not so common, the mineral deficiency amongst livestock has not gone away and continues to be difficult to diagnose.
Iodine deficiencies are now more commonly seen in beef than dairy herds, as iodine teat dips are often used in dairy farming which helps to maintain a sufficient level of the mineral within their system. Amongst beef herds an iodine deficiency is often presented as calf losses, meaning the careful monitoring of diets and mineral levels in your livestock is the best preventative solution to this otherwise costly problem. It is also always advised that where significant losses at calving, of greater than 5% occur, tests for deficiencies are investigated with your local veterinary surgeon.
The two most common causes of iodine deficiency are a lack of dietary iodine, or high levels of Iodine-antagonists in the diet. Iodine-antagonists include very lush grass after excessive slurry or inorganic fertiliser application and a high Calcium intake but are most often associated with eating brassicas such as kale, rape, cabbage, brussel sprouts and root tops. The very wet weather in recent years has also resulted in significant leaching of minerals from the soil, and consequently mineral deficiencies are being diagnosed on many farms where they have not been present before.
Iodine is an important mineral for your herd as it is used in the thyroid gland to produce hormones which accelerate reactions in most organs, thereby increasing metabolic rate and accelerating growth. Iodine deficiency in breeding animals may result in poor fertility, increased retained cleansings, and the birth of weak or dead young. It is also worth noting that dead young will not always present with an obvious goitre, and so this should not be relied upon as an indicator of iodine deficiency. You may also see reduced growth rates in your youngstock.
If you think that your stock may be deficient in some minerals than we recommend blood sampling 6 animals 2-3 months prior to calving to check their Selenium, Copper and Iodine status. Blood sampling at this stage is ideal as there is still an opportunity to treat for a deficiency during the remainder of the pregnancy, as mineral supplementation does not necessarily have instant results, so timing is key to ensure levels can be increased ahead of calving. Females grazing brassicas in late pregnancy or the breeding season will require supplementary iodine in addition to the provision of grass run-back or alternative forage.
Whilst there are iodine supplements on the UK market in the form of boluses or bullets, these have shown to not always be adequate for breeding cattle. Oral drenches, if dosed correctly, have shown to be more effective, however these do need to be used every 2-3 weeks. The ‘gold standard’ that we recommend for iodine supplementation is a pour-on of 7-8ml of 5% tincture of Iodine. This should be applied onto the thin skin of the pocket of the flank fold once a week for 5 weeks before calving as well as before and during breeding. This is a cheap, safe (for the cow, but mind those hind feet!) and effective method of supplementation. Through using this method of application, some of this iodine is absorbed through the skin and some is licked off and taken orally.
Unfortunately, whilst supplements can be provided to your herd where deficiencies are identified, in the case of animals born with goitre the damage caused is permanent, and they are not able to respond to supplementation provided. It is also worth noting that the application of iodine to the soil or pasture is not recommended as plant uptake is poor and the iodine will quickly be leached from the soil.
If you would like to discuss mineral deficiencies or supplementation in more detail, please contact the practice on 01392 872934 or email [email protected]