Alternatives to Antiparasitics in Sheep Farming
Combating Digestive Strongyle Resistance in Sheep: A Multifaceted Approach
PARIS – The increasing resistance of parasites to treatment is making it progressively more challenging to combat diseases caused by digestive strongyles in sheep across France and Europe. The consequences are notable, including a reported 22% drop in the daily average weight gain in lambs and a 23% decrease in milk production in ewes. Experts suggest that instead of seeking a single “miracle molecule,” a enduring, integrated approach to managing parasitic infestations is crucial.
During a recent webinar organized by the sheep sector committee and the Institute of Livestock (Idele), as part of the UMT Health Piloting of Ruminants program, three key strategies for managing parasitic infestations were emphasized. These recommendations are based on the findings of several multi-center research projects.
Limiting Pasture Infestations
One primary strategy involves implementing a reasoned approach to pasture management. According to Carole Tocze, a veterinarian at Idele, the goal is to maintain a population of parasites that remain susceptible to treatments, thereby preventing the spread of resistant strains.
Systematic treatment of entire flocks introduced to healthy pastures should be avoided. This practice can inadvertently allow resistant strongyles to survive and contaminate the pasture with resistant larvae. Similarly, moving animals to a clean pasture instantly after collective treatment should also be avoided.
Tocze advises selecting animals for treatment based on criteria such as age (young animals are typically less immune), body condition, or coprological results. The parasitic cycle can last from one week to three months, depending on environmental conditions. Optimized pasture rotation is therefore essential to minimize re-infestation. Ideally, animals should not be returned to the same pasture within two months.Returning animals to a pasture after only fifteen days allows excreted eggs to develop into the infective stage.
Overgrazing should be avoided, and young animals should not remain on the same plot for extended periods. Adjusting herd density to match grass growth is also recommended.Integrating immune sheep with susceptible animals, as well as implementing mixed grazing with cattle, can further reduce the parasitic load.
Enhancing Animal Resistance and Resilience
Another key approach focuses on improving the inherent resistance and resilience of sheep. Genetic selection offers promising avenues, as resistance to parasites is a heritable trait. Certain dairy breeds,such as the red head Manech and Basco-Béarnaise,already have genetic indexing for this trait.
Since 2024, a phenotyping system has been used to identify the most resistant individuals within the Lacaune milk breed. For meat sheep,phenotype-based classifications exist for several breeds. The long-term objective is to establish a comprehensive genetic evaluation system to select breeding stock that are more resistant to strongyles, without compromising overall performance.
Strategic Strongyle Elimination
the elimination of strongyles relies on the judicious use of treatments. The Agir method outlines best practices: alternating anthelmintic drug families,managing and targeting treatments through coprological monitoring,preventing the introduction of resistant parasites through quarantine measures,and adhering to dosages appropriate for the weight of the heaviest animal in the group,rather than the average weight.
By combining these diverse strategies, livestock managers can more effectively control parasitic infestations and slow the development of resistance to treatments.
Combating Digestive Strongyle Resistance in Sheep: A Q&A Guide
What are digestive strongyles and why are they a problem for sheep?
Digestive strongyles are parasitic worms that infect sheep, causing a disease that makes it difficult to combat. According to the source article, the critical issue is the increasing resistance of these parasites to treatment, which is making it more challenging to control strongyle infestations.This growing resistance leads to meaningful consequences, including a reported:
22% drop in the daily average weight gain in lambs.
23% decrease in milk production in ewes.
What is being done to address the problem of strongyle resistance?
Experts are advocating for a shift away from relying on single “miracle molecules” and instead embracing a multifaceted, integrated approach to managing parasitic infestations. This approach focuses on three key strategies.
What are the three key strategies for managing strongyle resistance?
The strategies, emphasized in a recent webinar organized by the sheep sector committee and the Institute of Livestock (idele), include:
- Limiting pasture infestations
- Enhancing animal resistance and resilience
- Strategic strongyle elimination
How can pasture infestations be limited to combat strongyle resistance?
A reasoned approach to pasture management is crucial, according to Carole Tocze, a veterinarian at Idele.The goal is to maintain a population of parasites that remain susceptible to treatments, preventing the spread of resistant strains. Several practices are key in this strategy:
Avoid Systematic Treatment: Do not treat entire flocks introduced to healthy pastures. this can unintentionally allow resistant strongyles to survive and contaminate the pasture.
No immediate Pasture Transfer: Do not move animals to a clean pasture immediately after collective treatment.
Targeted Treatment: Select animals for treatment based on criteria such as age (young animals are typically less immune), body condition, or coprological results.
Optimize Pasture Rotation: Because the parasitic cycle can last from one week to three months, depending on environmental conditions. Animals should ideally not return to the same pasture within two months to minimize re-infestation.
Avoid Overgrazing & Match Herd Density: Prevent overgrazing and avoid young animals staying on the same plot for extended periods. Aim to adjust herd density to match grass growth.
Mixed Grazing: Integrating immune sheep with susceptible animals, as well as implementing mixed grazing with cattle, can further reduce the parasitic load.
How does enhancing animal resistance and resilience help combat strongyle resistance?
Improving the inherent resistance and resilience of sheep helps to combat strongyle resistance. Genetic selection offers promise hear, as parasite resistance is a heritable trait.
Are there sheep breeds that are already more resistant to strongyles?
Yes, certain dairy breeds already show resistance. For example, the article mentions:
The red head Manech
Basco-Béarnaise
These breeds have genetic indexing for this trait.
What is a phenotyping system?
A phenotyping system is being used to identify the most resistant individuals within the Lacaune milk breed since 2024. It’s a method of categorizing animals based on their observable characteristics (phenotypes) to identify those that show resistance to parasites. Phenotype-based classifications also exist for meat sheep breeds. The long-term goal is a comprehensive genetic evaluation system to select breeding stock with higher strongyle resistance without harming overall performance.
What does “strategic strongyle elimination” involve?
Strategic strongyle elimination involves the judicious use of treatments, following best practices outlined by the Agir method. This method includes:
Alternating anthelmintic drug families.
Managing and targeting treatments through coprological monitoring.
Preventing the introduction of resistant parasites through quarantine measures.
Adhering to dosages appropriate for the weight of the heaviest animal in the group, rather than the average weight.
Can you summarize the key approaches to managing strongyle resistance?
| Strategy | Description |
| :——————————– | :—————————————————————————————————————————————————————————————————————— |
| Pasture Management | Implementing pasture rotation, avoiding overgrazing, and adjusting herd density to reduce parasite load. |
| Genetic selection | Utilizing genetic indexing, phenotyping, and developing comprehensive genetic evaluation systems to breed sheep with enhanced resistance to strongyles. |
| Judicious Treatment | Employing the Agir method, including alternating anthelmintic drug families, coprological monitoring, quarantine, and accurate dosage calculation based on animal weight.|
Why is a multifaceted approach important?
By combining these diverse strategies, livestock managers can more effectively control parasitic infestations and slow the development of resistance to treatments.