28 May 1999

Thoughtful strategies bring success in control of worms

CLEAN pastures, strategic grazing and timely drenching are enabling one Shrops sheep producer to keep on top of worms and maximise lamb growth rates at grass.

John Parry has 350 Mule ewes and 70 Hereford cross heifers at his Donington Farm near Wolverhampton. When IACS introduction reduced flexibility for grazing sheep and cattle within the 160ha (400-acre) arable rotation he decided to rent 34ha (85 acres) of grass, rotated with cultivated roses from the David Austin rose company.

"Leys last for a minimum of five years before they are ploughed in and planted with roses," says Mr Parry. "After two years the rose land is returned to grass ensuring clean pasture for early lambs."

Lambing starts on Mar 1 and ewes with single lambs have priority over new grazing. "I aim to sell the earliest singles by the end of May, and with the right conditions I wont need to worm them," he says. "The greatest economy in worm control is being able to finish lambs quickly so you do not have them to drench."

But worm control in the flock starts long before lambs arrive. Ewes are wormed before tupping, in early September with a white drench containing selenium and cobalt. According to Shrops sheep vet Chris Lewis, cobalt deficient pastures increase susceptibility to parasites, so using a drench which includes cobalt can be beneficial.

Any new stock are given ivermectin. "Ivermectin has the advantage of cleaning out any inhibited worms," says Mr Lewis. Fluke is not a problem on the farms light and free-draining soils.

Ewes are housed in early December and wormed with ivermectin two weeks later. Mr Parry uses different wormers in the same year, which differs from the more conventional practice of changing yearly. He believes using ivermectin once a year will reduce the flocks worm burden.

"It is important to ensure ewes are wormed before turnout to avoid the rise in numbers of eggs shed by ewes after lambing. Whether worming shortly after housing or at lambing makes any difference is still a matter for debate," says Mr Lewis.

Although Mr Parry worms lambs every three weeks from mid-May to mid-July, thoughtful grazing management is also key to effective parasite control. Stocking rate, grazing with cattle and using aftermaths and arable by-products in autumn all help.

Sheep are set-stocked at 13 ewes with twins a hectare (six/acre). Despite this modest stocking rate, Mr Parry reckons feeding ewes for longer is beneficial. This enables him to get early lambs away sooner, reducing stocking rates and worm burden. "We feed cows to produce milk, so I do not understand why farmers are so reluctant to feed ewes to do the same," he says.

Grazing ewes and lambs with his beef heifers also helps Mr Parry to keep the worm burden low.

Mr Lewis explains: "Larvae crawl to the bottom of grass blades during the day and to the top when it is cool and damp. On dewy mornings sheep can pick up larvae, because they nibble grass from the top. Cattle pull grass from the bottom, removing larvae that infect sheep. Fortunately these larvae are harmless to cattle."