Sustainable Anthelmintic Use

At Tanygraig, a long-standing commitment to data-driven farm management has led to the recording of flock performance from birth. The dataset provides a foundation for informed decision-making, and the natural progression for the farm was to capitalise on the data captured for enhanced parasite management strategies.

Recognising the need to preserve the efficacy of available anthelmintics, Tanygraig is embracing technology by integrating an auto-calibrated dosing gun. This device will connect with the farm's lamb weigher, automatically adjusting the anthelmintic dose according to each lamb's weight, ensuring accurate administration.

Complementing this will be the practical application and benefits of a Targeted Selective Treatment (TST) strategy, combining lamb performance and faecal egg counts (FEC) to determine which lambs require treatment. Our aim is to illustrate how TST can effectively protect drench efficacy while minimising any potential negative impact on lamb performance. Furthermore, a significant objective of this project is to quantify the economic advantages of combining the auto-drencher with a TST strategy. We will calculate the monetary savings achieved compared to the traditional practice of drenching entire mobs of lambs based solely on pooled Faecal Egg Count (FEC) sampling results.

The project will contribute to the Sustainable Land Management outcomes including:

• High animal health and welfare
• Resource efficiency

Final update

Key results

• Dosing all lambs to the heaviest animal is the least cost-effective method.
• Splitting lambs into three weight groups reduced wormer use by 22–24%, saving £200–£240 across the 2025 season.
• Using an auto-change dosing gun saved an additional 8–9% (around £85–£89) compared to the three-group method.
• Weigh accuracy is critical—incorrect weights can lead to under dosing and resistance risk.
• Auto-change guns offer labour efficiency but require higher investment and ongoing maintenance.

Background

SCOPS guidelines recommend treating sheep to the weight of the heaviest animal in a group to avoid underdosing and slowing resistance development. However, large weight variation—especially before weaning—can lead to significant overdosing and unnecessary cost. Tan Y Graig trialled alternative dosing strategies in 2025 to determine practical and economic benefits to their system.

Purpose of the work

• Whilst the initial purpose of the project was to implement a Targeted Selective Treatment (TST) strategy, the project changed its course to compare three approaches to wormer administration: 

1.Dosing the heaviest lamb in the group
2.Splitting animals into three weight-based subgroups
3.Using an auto-change dosing gun

• To quantify cost differences and identify practical benefits and limitations of each method.
• To support improved anthelmintic utilisation while reducing unnecessary medicine use and cost.

What we did

• Checked accuracy of weigh scales using calibrated weights.
• Weighed all lambs throughout the season (May–Nov 2025) to capture variation in liveweight.
• Compared wormer costs using real price data from veterinary suppliers.
• Calculated wormer usage and cost under: 
  • Blanket dosing the heaviest
  • Three weight sub groups
  • Auto-change dosing gun delivering individual liveweight doses
• Documented labour, equipment and software requirements for each approach.

Outcomes

• Three subgroup dosing delivered the greatest cost savings relative to investment—accurate, low-tech, and accessible for most systems.
• Auto-change dosing gun improved accuracy and speed but required: 
  • Approximate £895+VAT upfront cost
  • Regular calibration, servicing and software compatibility
  • Reliable weigh scale accuracy
• Auto change technology would take 4–5 years to pay back at Tan Y Graig based on wormer savings alone.
• Full group dosing risked substantial overdosing due to wide weight variation (up to 20kg differences at some sessions).

How to apply on your farm 

1. Weigh animals regularly and ensure scales are checked for accuracy at the start, middle and end of each session.
2. Split lambs into at least three weight groups post weaning to improve dosing accuracy and grazing management.
3. Dose each group to the heaviest animal within that sub group, not the whole flock.
4. Consider auto-change dosing guns if saving labour/time is a priority and the flock size justifies the investment.
5. Record weights and treatments electronically (EID + software) to monitor DLWG and refine management decisions.

Please contact timtechnegolcff@mentera.cymru if you would like to receive a copy of the full report.  

• October 2025