Sustainable worming improves lamb growth rates

Sustainable worming improves lamb growth rates

A comprehensive, integrated worming programme has delivered better growth rates and healthier lambs for Robin and Mandy Kellett from Parkhill Farm in Northamptonshire, contributing to a more efficient and successful farming enterprise.

Robin is not only a sheep farmer, but also a knowledgeable Registered Animal Medicine Advisor (RAMA) for Mole Valley Farmers, which gives him a unique perspective on anthelmintic use.

“Being a farmer gives me a huge advantage when prescribing products, because I can relate to what’s going on with my own stock. This helps me understand what might be going on at someone else’s farm and I can advise customers with first-hand experience,” he says.

“I always consider environmental factors when looking at worm control. To minimise worm burdens from the start, every lamb on our farm is first turned out onto fresh pasture, achieved by rotational grazing. Once weaned, lambs often graze silage aftermath to provide more ‘clean’ pasture.

“Following this, I look at my worming programme. Until recently we used a macrocyclic lactone (clear) wormer on the lambs, but we started using Zolvix™ after I carried out some research into sustainable worming strategies.”

Zolvix is an oral anthelmintic treatment, and the first active ingredient from the 4-AD (orange) drench class. It has a unique mode of action which differentiates it from the older wormers, as it is effective against nematodes that are resistant to other products. The broad spectrum treatment is effective against all of the economically important gastro-intestinal worms in sheep.

At Parkhill, the ‘orange’ wormer is used for two categories of sheep. Although the flock is mostly closed, rams are occasionally purchased. These rams are quarantined in a shed before mixing with other sheep and are treated with Zolvix to clear out any resistant worms before they are turned out, reducing the risk of contaminating pasture.

Using a new generation wormer like Zolvix may slow down the rate of wormer resistance building, which will increase the longevity of the older wormers on the market. Reducing resistance has benefits beyond the efficacy of anthelmintics, as it negatively impacts performance.

Robin also uses the wormer as a mid to late season treatment to set up weaned lambs for the winter. This is sometimes done in conjunction with foot-bathing or mineral bolusing (depending on the season) and so fits in with the calendar of tasks on farm.

“Since using Zolvix we’ve noticed a real improvement in lamb growth rates,” he says.

“We use it across all our lambs, and it gives them a good clear out of any worm burden. After administration, they keep cleaner and grow better.”
Untreated worm burdens can negatively impact lambs, reducing their ability to thrive. Signs include a depressed appetite, less feed intake and reduced growth rate. Permanent gut damage reduces the rate of nutrient absorption and can cause scouring.

The result of scouring is impaired mineral retention, which causes a small skeleton and can exacerbate trace element deficiencies. Worm burden and the subsequent scouring also leads to depressed feed intake and poor protein metabolism, which can reduce muscle growth and depress carcass quality.

Therefore, managing worms through a strategic anthelmintic programme and following best practice is crucial to keep lambs healthy, happy, and growing. It can also protect the flock from imported resistant worms through use in quarantine. Robin and Mandy use both approaches to keep their flock performing optimally at all stages of life.


ZOLVIX™ 25 mg/ml oral solution for sheep. Legal category: POM-VPS in UK. Information regarding the side effects, precautions, warnings and contra-indications can be found in product packaging and leaflets; further information can also be found in the Summary of Product Characteristics. Advice should be sought from the medicine prescriber. Zolvix, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. Use medicines responsibly ( © 2021 Elanco or its affiliates. PM-UK-21-0579. Date of Preparation: June 2021

To develop the most effective and sustainable worming programme for your flock, speak to one of our specially trained Registered Animal Medicines Advisors (RAMA). For further information about Zolvix, visit: