Explore selective deworming strategies for optimal herd health and sustainable parasite control in lambs and goats. Dr Duncan Houston, vet, 2025.

🐑 Selective Deworming for Lambs and Goats: Smart, Sustainable Parasite Control

By Dr Duncan Houston (vet, 2025)

Grazing lambs and meat goats commonly face gastrointestinal parasites that can impact growth, immunity, and overall herd performance. A sustainable solution lies in selective deworming—treating only animals that show signs of anemia—rather than blanket deworming, which can drive resistance. This method, combined with protein supplementation, may enhance the flock’s natural resistance.

🎯 Why Selective Deworming?

Gastrointestinal parasite resistance continues to escalate in small ruminants, especially Haemonchus contortus (“barber-pole worm”). Frequent deworming spikes resistance, making treatments less effective.

Selective deworming targets only the individuals most in need—those with moderate to severe anemia—based on the FAMACHA scoring system. This reduces drug use, delays resistance, and keeps susceptible parasites around to compete with resistant ones 👌.

📋 The FAMACHA Scoring Method

• Scores range from 1 to 5.
• 1–2 = healthy red mucous membranes → no dewormer.
• 3 = moderate paleness → treat.
• 4–5 = serious anemia → immediate treatment.

This method empowers farmers to make informed decisions and minimizes unnecessary drug use.

🔬 The 3-Year Study Setup

Researchers tracked six grazing groups, each with 18 animals (6 Suffolk lambs, 6 Katahdin lambs, 6 meat goats). Groups were split:

• 3 non-supplemented
• 3 supplemented with whole cottonseed

At turnout, all animals received anthelmintic treatment (valbazen, levamisole, ivermectin). Then, only individuals with FAMACHA score ≥3 were selectively re-treated.

📈 Findings: Breed Resilience & Supplement Impact

1. Katahdin lambs – highest parasite resistance. Few required retreatment.
2. Suffolk lambs – moderate resilience.
3. Goat kids – most susceptible to parasites.

Protein supplementation (whole cottonseed) effectively reduced fecal egg counts in goat kids—supporting immunity. It had less impact on Katahdins, which already showed strong resilience.

🔁 The Role of Protein in Parasite Resistance

Protein is crucial for:

• Building hematological components.
• Driving immune responses.
• Repairing damaged gut tissue.

Whole cottonseed delivers a high-protein and energy boost. In susceptible species like goats, this dietary support helps manage parasite burdens and anemia more effectively.

🌾 Breed Differences Matter

• Katahdin lambs: Naturally parasite-resistant—ideal for low-input systems.
• Suffolk lambs: Need moderate parasite control measures.
• Goat kids: Require more proactive nutritional and deworming strategies.

✅ Implementing Selective Deworming on Your Farm

1. Train staff to use FAMACHA scoring monthly.
2. Treat only animals scoring ≥3.
3. Incorporate high-quality protein supplements for vulnerable animals.
4. Monitor fecal egg counts to assess parasite loads.
5. Rotate anthelmintics based on FEC results to curb resistance.

🛠️ Managing Anthelmintic Resistance

• Use combination treatments only when necessary.
• Maintain refugia—untreated animals to preserve susceptibility in parasite populations.
• Track effectiveness via FEC 14 days post-treatment.

🌍 Sustainability & Herd Health

Selective treatment aligns with:

• Improved animal welfare – treating only when needed.
• Economic savings – reduced medication costs.
• Industry responsibility – mitigating anthelmintic resistance.

Protein supplementation supports sustainable health and performance metrics over time.

📊 Example Flock Implementation

Monthly Timeline

1. Inspect grazing areas for height and wetness.
2. Score each animal with FAMACHA.
3. Record scores & body condition.
4. Treat those scoring ≥3 with appropriate dewormer.
5. Administer protein supplements to susceptible groups.
6. Recheck FAMACHA and FEC after 10–14 days.
7. Make adjustments for next cycle.

💬 Common Questions

Is this method labor-intensive?

No—scoring takes about 30 seconds per animal.

How much supplement to provide?

Consult a ruminant nutritionist—typically 0.5–1 lb/day per animal.

Are FEC tests necessary?

Yes, periodic fecal egg counts help validate efficacy and resistance management.

📚 Further Reading

For in-depth detail, consult veterinary ruminant parasitology journals, extension bulletins, and university resources.

🌟 Final Takeaway

Selective deworming guided by FAMACHA scoring, combined with targeted protein supplementation, offers a smart, economical, and sustainable strategy to manage parasites in lambs and goats. Tailoring the approach to breed resilience makes the method even more effective—and preserves long-term anthelmintic efficacy.

— Dr Duncan Houston (vet, 2025)