Using a bolus can overcome ‘hit and miss’ mineral intake levels

Sheep producers using a bolus to achieve an effective sustained release of trace elements and minerals are overcoming the “hit and miss” intake levels that can be associated with free-access availability of mineral supplements.

And such improvements are particularly marked in sheep flocks grazing land where there are significant mineral imbalances. In fact trials undertaken in a Cumbria flock where there has been a known shortage of iodine, showed the use of the bolus slow-release system achieved marked improvements in performance.

Jamie Venison, technical director with Agrimin, says sustained release of minerals by using a single bolus – costing about £1 a ewe – delivers the largest available daily supply of iodine and a ewe’s total daily requirement of selenium and cobalt.

Case study: David Lawton

Greystoke Castle Farms, Penrith, Cumbria

Farm manager David Lawton has seen a reduced number of barren ewes, higher lambing percentage and improved lamb weaning weights since starting bolusing the 2,400-ewe flock at Greystoke two years ago.

The flock includes 800 pure Swaledales and 1,500 North Country Cheviots, run on a system which relies on grass and feeds only a little cake in the run up to lambing, with all ewes lambed outside.

The trial focused on the farm’s Swaledale shearling gimmers which were treated with an iodine, selenium and cobalt bolus, which was free of copper.

Mr Lawton says: “We haven’t used boluses in our sheep at Greystoke before and always relied on drenches to maintain the mineral and trace elements we needed, but the trial results have shown us that the bolus treatment provides a more effective method of sustained release compared with traditional drenching.”

Each bolus – which has a 180-day life – provides 4mg of iodine a day plus 0.4mg of selenium and 0.8mg of cobalt.

Mr Venison says: “Widespread research has shown that increased lambing percentage is linked to feeding the correct levels of minerals and trace elements, but it’s essential that these are delivered consistently – and the bolus achieves that.

“At Greystoke Caste Farms the treated ewes showed a 12% increase in lambing percentage while lamb weaning weights were up by 2kg per head. The number of barren ewes also fell by 5%.”

Case study: Stephen Welton

Green Farm, Coddington, Ledbury, Herefordshire

A selenium deficiency was affecting lambing percentage in Green Farm’s 1,000 Romney ewes and despite undertaking an on-going selection programme for flock replacements based on prolificacy, the scanning figures were pegged at about 160%.

We’re on sandstone and the land here is very low in selenium, says Mr Welton, who lambs outdoors and uses Ile de France, Berrichon du Cher and Hampshire Down rams on 60% of the flock.

“The selenium shortage was causing us a major problem in terms of lambing percentage – we should have been at 185%-190%, but even though we we’re drenching the ewes pre-tupping we weren’t seeing any improvements. And on top of that we had a very long drawn-out lambing period.”

Ewes were initially treated with a bolus two weeks before tupping, but lambing percentage only improved by barely 5%.

The decision was then made to bolus the flock five weeks before tupping and consequently the farm saw an immediate increase in lambing percentage the following spring. “We jumped 30% to achieve an overall lambing percentage of 190% in the first season and we’ve maintained that for the last three years by following the same procedure.

“Ewes are healthier, lambing time is now very tight – about 12 really busy days – and lambs are much more vigorous at birth.”

Mr Welton says the general health and appearance of the flock has also improved. “The sustained release achieved by the bolus is far more effective than relying on free-access minerals. We were also getting some white muscle disease in our lambs so we’re now treating ewes with a second bolus in February/March to give them a selenium boost and it has sorted out the problem.”