Worms are a constant challenge and have a significant impact on stock production. We rely on drenches in young animals to manage their parasite challenge until their immune system matures enough to have a significant impact. A diet containing high quality proteins helps lambs to counter the impact of worms while also supporting high growth rates.

Preparing weaning paddocks by reducing the worm challenge also contributes to improving lamb growth rates. An effective drench removes the adult and larval worms in the lamb, allowing the gut to heal and function normally. As the lamb eats more worm larva found in pasture, these quickly cause more irritation and damage resulting in lower lamb growth rates.

It takes three weeks for the newly ingested larva to develop into adult worms and breed so there will not be any eggs in the lambs’ faeces for these three weeks. This is important as it reduces the worm contamination in the paddocks grazed in those three weeks. Cross grazing with cattle, grazing undrenched adult low body condition ewes in the lamb grazing rotation, cutting silage or specialist summer forages are all good options for reducing worm challenge.

It is important that every drench you use is as effective as possible, which I know sounds logical. To determine the effectiveness of the drench, collect at least 10 individual faecal samples from lambs one to two weeks after drenching for a faecal egg count. If there are eggs present, this indicates adult worms are still in the lamb. This is a warning to check that your drench gun is calibrated correctly and working reliably.

A second failed test is a strong indicator that you have worms resistant to that drench combination and these worms are breeding and spreading their genetics over your farm resulting in your lambs not growing as fast as they could.

Quarantine drenching prevents the introduction of drench resistant worms onto your farm. Zolvix™ Plus is one of only two effective and registered quarantine drenches in New Zealand as it contains an active that is not present in routine drenches. This concept is vital in trading and finishing systems and anyone purchasing sheep.

Triple combination oral drenches containing an active from each of the main drench groups (ML, BZ and Levamisole) are your best choice for routine drenches. Having three highly effective drench groups present at the same time significantly slows the development of drench resistance. Good worm refugia management is also essential.

To discuss your lamb drenching programme this summer, contact your local PGG Wrightson Technical Field Representative.