Time to apply cobalt to enhance young stock growth

 
Spring is the best season to apply cobalt to enhance young stock growth

 Farmers raising young stock through the spring should not let healthy grass growth divert them from the need for an application of cobalt onto pastures.

‘You have to get the timing right,’ advises Warwick Catto, Head of Research & Environment at Ballance Agri-Nutrients. ‘October and November are the best months for cobalt application to resolve any growth issues with young stock, especially lambs.

’Put it on now while there are young animals around and it will peak in the next four to six weeks, before tapering off. It has a very short availability in the soil, and only a small part is taken up by plants – the rest is excreted.’

He says the degree of cobalt deficiency will vary from year to year. In a spring with rapid pasture growth, the cobalt taken up from the soil will be diluted and there will be less cobalt-containing clover in the sward.

‘Although not important for plant production, other than as minute amounts for rhizobia bacteria in clover, cobalt is very important to the grazing animal. In particular it makes it possible for rumen microbes to synthesise vitamin B12, enabling digestion of plant material.

‘The vitamin B12 is absorbed and stored mainly in the liver of the grazing animal. In the first few weeks of life the lamb or calf is dependent on the vitamin B12 stored in the liver during pregnancy, plus any vitamin B12 in the milk. The young lamb is extremely sensitive to cobalt deficiency.’

Mr Catto says the most striking feature of any B12 deficiency is loss of appetite and poor growth rates, with lambs being most susceptible in late spring-summer in the North Island and summer-autumn in the South Island.

‘The deficiency signs in lambs are relatively easy to spot, with afflicted lambs exhibiting impaired growth rate and wool growth, along with signs of anaemia in severe cases. You can see there’s something wrong. Often the lambs have crusty ears and watery eyes as well.’

Cobalt deficiency historically occurs on four main soil types in New Zealand: sandy soils in Northland, the pumice soils of the central plateau, the yellow brown earths near Nelson, and on sedimentary soils in Southland, but it can be found more widely and levels should be monitored as part of a normal animal health programme.

‘Soil tests are inadequate for determining cobalt deficiency. It is best to rely on plant analysis. Collect a 0.5-0.6 kg sample of mixed pasture from the representative paddocks for analysis. Cobalt levels are adequate if greater than 0.1 ppm in the pasture.

‘If pasture analysis reveals that cobalt levels are on the low side, stock should be tested using either a blood or a liver sample from a minimum of 10 animals for confirmation. Farmers then need to determine the most cost-effective way of getting cobalt to their stock.’

Ballance supplies granulated cobalt (10% active ingredient). The typical maintenance application rate is 375 gm/ha every second year. Capital dressing is twice this rate at 750 gm/ha. At current pricing (October 2010) of $24.27/kg for Granular Cobalt, the maintenance treatment equates to $9.10/ha per application.

ENDS

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