2 May 1997

Rain brings risk

of nematodirus

RECENT rain could increase risk of a mass hatch of nematodirus on pasture grazed by sheep last year.

Young lambs are most vulnerable and need dosing once or twice in May, even if ewes have been treated with the new wormer Cydectin.

Used at turnout, or when ewes are out onto grass to be set-stocked until weaning, Cydectin, which prevents reinfection for four to five weeks, will help ewes clean up pasture for growing lambs, says Brian Hosie of the Scottish Agricultural College in Signets Beef and Sheep Notes. But he warns that it has no persistent effect against nematodirus. Young lambs will need treating with this product as well as ewes, or with one of the cheaper white drenches – Panacur, Systemex, Valbazan, or Bayverm; a levamisole drench or Oramec.

When using group one wormers, Mr Hosie suggests placing the dose over the back of the throat rather than in the mouth to increase effectiveness. Dividing the white drench into two equal doses given 12 hours apart can also increase results.

"Take care to ensure both doses are given – under-dosing is worse than not dosing in encouraging worm resistance," he says.

&#8226 Producers calibrating wormer dosing guns (Livestock, Apr 18), should ensure they use their chosen wormer for accurate calibration.