We hear nutritionists talk about our own healthy nutrition to get a ready source of trace minerals. So too is it for our pastoral grazing animals.

The 'big five' that are referred to in New Zealand – cobalt, selenium, copper, iodine and zinc are often a reflection of the soil and pasture concentrations. Fortunately in the Katikati region, we have soils that have originated from the Waihi and Gisborne ash showers.

They tend to have inherently higher levels of cobalt and selenium compared to the volcanic eruptions of Taupō and Kaharoa.

The rhyolite and pumice have low levels and weather slowly. Observations by local farmers describe the change in soil types at Apata whereby the river beds change from boulders to silt as you travel eastwards to Tauranga. No wonder cobalt deficiency was called "Tauranga Disease".

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For sheep and cattle, cobalt is an essential trace element involved in energy metabolism, the loss of appetite and decrease in live weight or growth are the most remarkable features. Given a boost from their mothers at birth and depleting their own liver stores, weaned lambs and calves are vulnerable to checks in growth from now on as they rely on sufficient supplies from grass.

Supplementation depends upon your farm history – soil type, fertiliser and soil/plant analysis. The results from tissue sampling of animals directly gives the true picture.

There are many ways to supplement — directly to animals or through soil and plant application. Injections, boluses, drenches, licks, capsules, pour-ons, additives and foliar.

Many products are available – some with published scientific and regulatory approval and others trading as compounds "Generally Regarded As Safe (GRAS)" with lesser regulation.
Diagnosing clinical deficiency of cobalt and selenium is rare nowadays but is something to consider when investigating suboptimal growth performance.