Goat Deworming: When, What, and FAMACHA Scoring

Routine Deworming Is Killing Your Goats — Here Is Why

I need to say something that is going to upset some goat owners: if you are deworming your entire herd on a set schedule — every month, every six weeks, every season — you are actively creating a drug-resistant worm population that will eventually be untreatable. I have watched entire herds crash because the owners did exactly what the feed store told them to do, which was deworm everything on a regular calendar. This advice, well-intentioned as it may be, is catastrophically outdated and is the primary driver of the anthelmintic resistance crisis in small ruminants.

In my practice, I have performed necropsy after necropsy on goats that were dewormed religiously and still died with guts packed full of worms that shrugged off every drug thrown at them. The worms won because the management approach selected for resistance at every turn. This article is going to teach you how to deworm selectively, intelligently, and in a way that keeps your drugs working for years instead of months.

The Enemy: Haemonchus contortus, the Barber Pole Worm

Before we talk about treatment, you need to understand what you are fighting. Haemonchus contortus is the number one killer of goats in warm and temperate climates worldwide. This parasite lives in the abomasum (the true stomach) and feeds on blood. Each adult female worm can suck 0.05 milliliters of blood per day and lay five thousand to ten thousand eggs daily. When a goat carries a heavy burden of several thousand worms, it is losing enough blood to become profoundly anemic. The goat does not die from the worms directly — it dies from anemia, hypoproteinemia (low blood protein causing bottle jaw and edema), and the secondary infections that overwhelm a weakened immune system.

What makes Haemonchus so dangerous is its life cycle speed. Eggs shed in feces can develop into infective larvae on pasture in as little as four to five days in warm, moist conditions. A single heavily parasitized goat can contaminate a pasture with millions of eggs in a week. And here is the kicker: Haemonchus has a tremendously high reproductive capacity, which means any genetic resistance to dewormers spreads through the population very quickly.

Why Routine Deworming Creates Resistance

To understand resistance, you need to understand a concept called refugia. Refugia refers to the population of worms that are NOT exposed to the dewormer — the ones sitting as larvae on pasture, the ones in untreated animals, the ones in a stage of development the drug does not affect. These worms in refugia dilute the resistant genetics in the overall population because they are drug-susceptible.

When you deworm every animal in your herd at the same time, you kill all the susceptible worms inside the animals. The only worms that survive inside the animals are the resistant ones. Those resistant worms then breed and produce resistant offspring. If you have also recently rotated to clean pasture (a common but misguided practice right after deworming), there is almost no refugia left — the only worms establishing on the new pasture are resistant. Within a few generations, your entire worm population is resistant to that drug class. I have seen operations lose an entire drug class in a single season with this approach.

FAMACHA Scoring: Treat the Individual, Not the Herd

The FAMACHA system was developed in South Africa specifically for Haemonchus contortus management, and it is the single most important tool in your deworming toolbox. FAMACHA is an anemia scoring system based on the color of the mucous membranes inside the lower eyelid. Since Haemonchus causes anemia, the color of those membranes tells you directly how heavy the worm burden is.

How to Score

Pull down the lower eyelid with your thumb and compare the color of the conjunctival mucous membranes to the FAMACHA card (you need the official laminated card — do not try to do this from photos on the internet; the color calibration matters). Score on a scale of one to five.

• Score 1 (Red): Optimal. This goat is handling its worm burden well. Do NOT deworm.
• Score 2 (Red-Pink): Acceptable. The goat is managing. Do NOT deworm.
• Score 3 (Pink): Borderline. Watch closely, recheck in one to two weeks. Deworm only if trending toward 4.
• Score 4 (Pink-White): Anemic. This goat needs to be dewormed.
• Score 5 (White): Severely anemic. Deworm immediately and consider supportive care (iron, B12, high-quality nutrition). This goat may also need a blood transfusion if the PCV (packed cell volume) is below 12%.

The Critical Point: Leave Scores 1 and 2 Alone

The goats that score 1 and 2 are your genetic goldmine. They are the animals with natural resistance or resilience to Haemonchus, and they are maintaining refugia — susceptible worms that dilute resistance in the population. When you deworm everything, you destroy this advantage. In a well-managed herd, seventy to eighty percent of the worm burden is carried by twenty to thirty percent of the animals. Treat only those heavy carriers, and you control disease while preserving drug efficacy.

Fecal Egg Counts: The Numbers That Guide Decisions

FAMACHA tells you about anemia right now; fecal egg counts (FEC) tell you about worm burden and, more importantly, whether your dewormers are actually working.

How to Collect and Run Fecal Egg Counts

Collect fresh fecal pellets directly from the goat (do not pick them off the ground where they could be contaminated or dried out). Use a modified McMaster technique with a saturated salt or sugar flotation solution. If you are running your own FECs — and I strongly encourage goat owners to invest in a basic microscope and McMaster slides — you count the eggs in a measured volume of fecal slurry and multiply by a factor (typically fifty) to get eggs per gram (EPG).

What the Numbers Mean

• Less than 500 EPG: Low burden. No treatment needed in a healthy adult goat.
• 500 to 2,000 EPG: Moderate burden. Treat if the goat is also showing clinical signs (poor body condition, rough coat, FAMACHA 4+, bottle jaw).
• Over 2,000 EPG: Heavy burden. Treat, especially for Haemonchus-type eggs.

Keep in mind that egg counts in goats do not correlate perfectly with worm burden in the way they do in cattle. A goat with 500 EPG of Haemonchus eggs may be in worse shape than one with 2,000 EPG of a less pathogenic species. Always interpret FEC results alongside clinical signs.

Fecal Egg Count Reduction Test (FECRT)

This is how you find out if your dewormers still work. Run FECs on a group of goats before deworming. Deworm them. Run FECs again ten to fourteen days later. If the egg count has dropped by less than 95%, you have resistance to that drug. If it has dropped less than 90%, you have serious resistance. This test should be done annually on every goat operation. It costs very little to run and can save you thousands in dead animals.

Drug Classes: Know What You Are Using and Why

There are only three classes of dewormers approved and widely available for goats, and most products are used off-label since very few anthelmintics are actually labeled for goats in the United States.

Benzimidazoles (White Dewormers)

Fenbendazole (Panacur/Safe-Guard) and albendazole (Valbazen) belong to this class. They work by disrupting the worm's cellular metabolism. Goats metabolize benzimidazoles much faster than cattle or sheep, so the cattle dose is inadequate. The recommended dose for goats is approximately twice the cattle dose — 10 mg/kg for fenbendazole (compared to 5 mg/kg in cattle) and 20 mg/kg for albendazole. Do NOT use albendazole in the first trimester of pregnancy — it is teratogenic.

Macrocyclic Lactones (Clear Dewormers)

Ivermectin (Ivomec) and moxidectin (Cydectin) are in this class. These drugs paralyze and kill worms by opening chloride channels in nerve and muscle cells. Again, goats need higher doses than cattle: ivermectin at 0.4 mg/kg orally (double the cattle dose) and moxidectin at 0.4 mg/kg orally. Always give these orally in goats. Injectable and pour-on formulations have erratic absorption in goats and contribute to subtherapeutic dosing, which accelerates resistance. Moxidectin is currently the most effective macrocyclic lactone against Haemonchus in most regions, but it is also your last line of defense in this drug class — use it judiciously.

Imidazothiazoles (Yellow Dewormers)

Levamisole (Prohibit/Levisol) works by causing spastic paralysis of the worms. Dose at 12 mg/kg orally. Levamisole has a narrower safety margin than the other two classes — overdose can cause toxicity (salivation, muscle tremors). Weigh your goats before dosing levamisole. In many areas, levamisole has maintained better efficacy than benzimidazoles or ivermectin precisely because it has been used less frequently. That does not mean it is resistance-proof.

Combination Deworming: The Protocol That Buys Time

When resistance to individual drug classes is confirmed or suspected, combination deworming — giving two or three drug classes simultaneously, not rotating them — has been shown to be more effective than any single drug alone. The principle is that worms resistant to Drug A are likely susceptible to Drug B, and vice versa. When you give both at the same time, you catch the worms that either drug alone would miss.

A typical combination protocol: fenbendazole at 10 mg/kg PLUS moxidectin at 0.4 mg/kg PLUS levamisole at 12 mg/kg, all given orally on the same day. This is not rotation. Rotation — using Drug A this time and Drug B next time — does NOT slow resistance and may actually accelerate it by selecting for multi-drug resistance sequentially. Give all classes together, at the same time, at the correct dose.

DrenchRite and Other Resistance Testing

If you want to know exactly which drugs still work on your farm, ask your veterinarian about a DrenchRite Larval Development Assay. This lab test exposes your worms to all three drug classes at multiple concentrations and tells you the percentage of resistance to each one. It is more expensive than a simple FECRT but gives you much more detailed information. It is especially valuable if you are bringing in new animals or if your FECRT results are ambiguous.

Pasture Management and Genetic Selection

No deworming program will succeed without pasture management. Larvae concentrate in the lower two inches of grass, so do not overgraze — maintain pastures at a minimum of four inches. Multi-species grazing with cattle helps because cattle consume goat-specific larvae without being harmed by them, effectively vacuuming the pasture. Allow pastures to rest for sixty or more days in hot, dry weather (UV light and desiccation kill larvae). Keep in mind that larvae survive much longer in cool, moist conditions.

Cull goats that consistently score FAMACHA 4 or 5. They are parasite sinks — genetically susceptible animals that contaminate pastures and require constant drug intervention. Select replacement stock from does and bucks that consistently maintain FAMACHA scores of 1 to 2 without treatment. Over time, you build a herd with inherent parasite resistance, which is the only truly sustainable solution.

Quarantine Protocol for New Animals

Every new goat that enters your property is a potential source of resistant worms your existing dewormer program has never encountered. The quarantine deworming protocol is non-negotiable: hold new animals on a dry lot or sacrifice paddock (not your best pasture) for at least seventy-two hours after arrival. On arrival, deworm with a combination of all three drug classes at goat-appropriate doses — fenbendazole 10 mg/kg plus moxidectin 0.4 mg/kg plus levamisole 12 mg/kg, all orally. The goal is to kill every worm the animal is carrying before it can deposit eggs on your pasture. Keep the animal on the dry lot for at least three days after deworming so that any surviving eggs pass onto the dry lot rather than your grazing pastures. After seventy-two hours, run a fecal egg count. If the count is zero, the animal can join the herd. If eggs are still present, the worms are resistant to your combination protocol, and you need to discuss options with your veterinarian before this animal contaminates your pastures with resistant genetics.

I cannot overstate the importance of this step. I have seen operations that spent years building effective deworming programs lose everything by bringing in one goat from a sale barn without quarantine deworming. The resistant worms that animal carried established on the farm and within a season, no drug worked anymore. Quarantine is cheap. Rebuilding a failed deworming program is not.

The Bottom Line

Stop deworming on a calendar. Start scoring FAMACHA every two weeks during parasite season, run fecal egg counts regularly, treat only the animals that need it, use the correct doses for goats (not cattle doses), and consider combination deworming when resistance is present. The days of picking up a tube of ivermectin at the feed store and running every goat through are over. If you keep doing it, you will run out of effective drugs, and then you will run out of goats. Targeted selective treatment is not complicated, but it requires you to look at each animal as an individual. Your herd depends on it.