Many farmers experiencing poor growth rates in weaned lambs put it down to a worm burden, but the problem may be more deep seated than that.
A recent trace element trial in Wales showed that selenium and cobalt deficiencies result in poor growth rates and can weaken immune systems.
Tom Blair, grassland products manager at Phosyn, says lambs will often pick up after worming due to trace elements in the drench.
However, this will only give a short-term response.
“A more satisfactory way of tackling deficiencies of these trace elements is by treating the soil, so that grass and clover contain enough to meet lambs’ requirements.”
More than 50% of UK pastures are deficient in cobalt, with 75% deficient in selenium, says Dr Blair.
Treatment with Grasstrac will replace these trace elements, along with copper, iodine, zinc and sodium.
A recent demonstration trial, carried out by Hybu Cig Cymru and IGER and funded by Farming Connect, showed a 13kg/acre difference in lamb production between deficient and supplemented groups.
Two groups of 100 Texel and Beltex cross weaned lambs were monitored for eight weeks between August and October last year.
One group grazed fields spread with Grasstrac Sheep Special – which does not contain copper, but has 70% more cobalt than normal Grasstrac – at 20kg/acre, while the control group grazed untreated pasture.
Host farmer Sion Jenkins, who runs 2400 ewes with his brother Rhys at Nantyclun, Brynberian, Pembs, says he was pleased with the results.
“I was impressed – unsupplemented lambs were quite poor in the end.”
Lambs which were not getting enough selenium and cobalt had suppressed immune systems and suffered from pining and weight loss.
Growth rates were 11% higher in lambs which grazed the treated pasture and they had better conformation and fat classification, with twice as many reaching the desired finish than the controls.
On average, Grasstrac lambs were 1kg heavier, with almost 80% reaching deadweights of more than 17kg, compared with just over 50% in the control group.
They also finished earlier and achieved £3.46 a head more than the control group – at a cost of 79p a head.
Both groups were drenched for worms at the start of the trial.
But the Grasstrac group had lower faecal egg counts later in the trial and only the control group required a second treatment in September.
This was possibly due to improved antibody response from the group treated with selenium.
Blood analysis showed the cobalt status of Grasstrac lambs was 64% higher than the controls at the end of the trial period, indicating effectiveness of supplementation.
The soil at Nantyclun has always been low in cobalt and in the past Mr Jenkins had drenched his lambs with a cobalt supplement.
“That cost 50-60p a head, but treating the grass is a lot less stress for lambs and is cheaper in terms of labour.
I will be using it again.”