Drench Cost Calculator Highlights Hidden Profits by Managing Wormer Resistance

Sheep farmers can now see first-hand the cost of using the wrong wormer on their farm thanks to a free online tool.


The Sheep Drench Cost Calculator from Zoetis will help farmers, in conjunction with their advisors, decide which wormers to use on their farm. The app demonstrates the potential loss in growth rate, labour and medicine costs, when the wrong product is used.

Resistance to sheep wormers is on the increase in the UK and every farm can have naturally occurring resistant worm populations.

Reduced drench performance due to resistance leads to more worms surviving and ultimately reduced lamb performance.

The calculator uses the latest UK resistance data or bespoke farm data so farmers can create specific drench plans with costs and return on investment information.

Although some wormers may be more expensive, the effectiveness against worms is likely to be higher because there is reduced resistance.


Effectiveness of wormers

For example, a white wormer may only have 50% efficacy and a yellow wormer, 65% efficacy, compared to a clear moxidectin type wormer (milbemycins), which is often greater than 95% efficacy.

The effectiveness of wormers will differ from farm to farm. Farmers that have done faecal egg reduction tests on their farm and know the effectiveness of wormers can input their own data into the app.

Ally Anderson, Zoetis Veterinary Consultant, says the idea of the app is to show farmers that investment in the right wormer is worth it, even if it may cost more.

“Wormers that are more effective can be more expensive, but when you are buying a wormer that isn’t that effective on your farm, it’s not just the cost of the wormer that you are losing, but production losses too, which often vastly outweigh the extra cost of the wormer.

“Ideally farmers should be working with their advisor and doing faecal egg reduction tests to see what the level of resistance is on their farm. This data can then be added into the app, instead of the UK average data, to give a more accurate picture,” she said.

Sheep farmer Tom Carlisle, Coxons Farm, Cracoe, Skipton, is lambing 500 Texel cross Mules and says when he used the app, he was shocked by the potential loss in production by using the wrong wormer.

“Just by doing something as simple as changing a wormer, it’s surprising how much money can be saved for the duration the lambs are on pasture, even if it means paying more for the wormer,” he said.


Increased profits

For example, in a group of 40 lambs grazing pasture for 120 days, and averaging £2 a kilo, if a white wormer at 50% efficacy was used, then the total cost of lost production compared to a drench with 100% effectiveness was £131.62.

This is in comparison to £13.51 when a clear drench with 95% effectiveness was used, so moving to a more efficacious drench gives a big potential return on investment.

The app can be downloaded from the Apple App Store or Google Play Store and is free of charge. You can also speak to your Zoetis Account Manager about the app.

How to guide to using the Sheep Drench Check app


1.Main menu 

Farmers and their advisors using the app have three options to begin with:

·         Drench Analysis, which allows quick input of farm information for a given drench to generate an analysis

·         Worm Plan Costs, which will provide details for multiple drenches to view cost comparisons

·         Resources, where users can review/open product brochures and relevant links to further information

2. Drench Analysis

Provide the simple inputs for the farm such as lamb price, days on pasture and worm challenge and press calculate.

For example, the lamb price was £2/kg, they spent 120 days on pasture and there were 40 lambs in the group. The worm challenge was medium on the farm.

3. Farm Results.

The results on this page tell you the growth rate difference in lambs compared to if you had used a product with 100% effectiveness.

For example, when using a wormer with 50% effectiveness compared to 100% effectiveness, the live weight difference at the end of the 120 days grazing, would equate to 6.71kg a lamb, or £13.42 a lamb.  Across the 40 lambs that’s a difference of £536.80.

4. Worm Plan Cost

To compare wormers, select a drench, and then either type in the effectiveness of the drench, if it is known on your farm or use the default, which is an average UK efficacy for that given drench. Input the data for each drench type being compared and click save. Once you have all the data for each drench, you can then press calculate.

5. Worm Plan Cost Results

For example, when a white drench with 50% effectiveness and a clear drench with 95% effectiveness were compared, the total cost of lost production compared to a drench with 100% effectiveness was £13.51 for the clear drench and £131.62 for the white drench.


It is then possible to edit the drenches in the plan to improve the potential productivity of the farm.