Declaring war on worm nightmare
Wormers, used correctly, can boost lamb growth and profits
Published 21/06/2011 | 05:00
Lambing is now over and ewes and lambs are happily outside grazing grass. The warm, damp weather we experienced this spring gave a great boost to grass growth.
However, it should be remembered that these conditions are also ideal for the development and transmission of the worm parasites that affect sheep and cattle.
Some of these worms will have survived the winter on the pasture; others will have survived in the ewes to be shed around lambing time when the ewe's immune system is compromised.
Lamb growth rates can be affected by heavy worm burdens even before they show signs of scouring, so treat ewes with a persistent wormer to reduce the threat.
Once lambs are 6-8 weeks old they should be dosed or dung samples should be examined for the presence of worm eggs. Traditional white, yellow and clear drenches need to be used every 3-4 weeks as they have no persistent activity in sheep.
Moxidectin drenches offer five-week activity and during this time all susceptible worms that are consumed are killed. Effectively, the lambs work as 'hoovers', cleaning the pasture of infective larvae. This allows the dosing interval to be extended to at least eight weeks. The other advantage of using a moxidectin is that lambs can be sent for slaughter 14 days after treatment, so it offers great flexibility when marketing lambs.
On many farms, the first worm to cause problems in the spring is nematodirus battus. This infection passes from one year's lamb crop to the next on the pasture.