The importance of Selenium and Iodine in the growing foetus and young calf.

The profitability of any beef or dairy enterprise is driven by performance. This starts with conception of the calf. As a calf specialist, I believe we should be improving tomorrow’s herd, today. If we take a step back and concentrate on the growing foetus, this is where all our efforts should be focused.

Pregnant dry cows not only require feed for maintenance and growth of the foetus, but also need building up ready for the next lactation and the next pregnancy. The udder needs time to repair, and adequate levels of minerals and vitamins at this time will have long term benefits for cow and calf. Low levels of selenium and/or vitamin E can lead to poor uterine muscle tone, prolonged calving, retained placenta and subsequent poor fertility. Selenium and vitamin E can cross the placenta so supplementing the dam will support the calf.

Lack of selenium in a calf causes ‘white muscle disease’ (WMD) with calves up to four months old having difficulty standing and stiffness walking due to weakened skeletal muscles. It can also affect the heart muscle causing sudden death. Those unable to suckle may die through starvation or secondary bacterial infection. Selenium and vitamin E act as antioxidants which protect cell membranes from breakdown.

Selenium and iodine are just two important trace elements which can have a significant impact on young calves. Iodine plays a large role in the development and growth of the foetus.  Like selenium, iodine deficiency can cause calves born weak or stillborn, or cows with low milk production thus increasing the rate of mortality in neo-natal calves. This is due to poor production of thyroxine, associated with an enlarged thyroid, commonly known as goitre.  Cattle grazing brassicas will need to be supplemented with iodine as brassicas contains substances called goitrogens, which interfere with thyroxine production.

Iodine deficient calves are often stillborn, have bald patches, with a large thyroid gland. Some farms with a selenium deficiency will show signs of iodine deficiency as the two are interlinked. Selenium is required to activate the thyroid hormones, so a selenium deficiency can lead to a secondary iodine deficiency.

Adequate trace element supplementation during the dry period will allow the cow to build up a plentiful supply of good quality colostrum which will have an effect on the lifelong performance of the newborn calf. Once the calf is born its only source of dietary selenium and vitamin E is through the milk, or milk replacer, so it’s important to choose a milk powder with adequate vitamin E. The ‘Wynngold‘ calf milk powders contain 500 i.u/kg in order to support the calf’s immune system. Where many calves from different farms are brought together there will be a significant challenge to their immunity.

Growing stock have a low requirement for iodine compared to pregnant and lactating animals, but pasture is often unable to fully satisfy requirements on its own. Therefore, supplementing trace elements with minerals, buckets and boluses is highly recommended.

In the past, antibiotics would be used to support weak and vulnerable calves but with the current drive to use less antibiotic, it’s now even more important to give young calves a strong immune system from birth, and give every calf a ‘fighting chance’. For further advice and technical support on meeting your herd’s nutritional needs, please contact either your local Wynnstay calf specialist or Wynnstay dairy specialist.

Sandy Wilson
Calf Specialist

Follow Sandy on Twitter @petticoatcalves, or contact your local specialist here.

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