I have been thinking about how to write this one for a while.
Not because the information is hard to find. It is out there if you know where to look. But because the story behind it is personal and I think the personal version is the one that actually sticks.
We bought ten sheep. We had lambs. We were excited about where it was headed.
A year later we had none.
We lost our entire flock to parasites. And when we sat down afterward and really looked at what happened, we realized that most of it was preventable. Not all of it. Farming always has a margin of unpredictability you cannot eliminate no matter how much you know. But most of it.
This newsletter is what we learned from losing those sheep. I am writing it because I think it will save some of you from going through the same thing, and because the parasite conversation in the sheep world is one of the most important ones a beginner can have before they buy their first animal.
What actually kills sheep on small homesteads
People worry about predators. They worry about disease. They worry about feed costs and fencing and all the visible, obvious things.
What kills more sheep on small homesteads than almost anything else is a worm you cannot see.
Barber pole worm, known scientifically as Haemonchus contortus, is a blood-sucking internal parasite that lives in the stomach lining of sheep and goats. It is particularly devastating because it does not cause obvious digestive symptoms the way some other parasites do. It causes anemia. It drinks blood, quietly, while the animal continues eating and moving around, appearing more or less normal until the burden gets heavy enough that the sheep crashes fast.
By the time most beginners recognize that something is seriously wrong, the worm load is already at a critical level. And in a small flock on a humid pasture in summer, once one animal is heavily infected and shedding eggs onto the pasture, the rest of the flock picks it up fast.
This is what happened to us. Not in one dramatic event. Gradually, then all at once.
The deworming mistake that made everything worse
Here is the part of our story that I want to be completely honest about because I think it is the part most beginners repeat without knowing the damage they are doing.
When we saw animals looking rough, we dewormed. The whole flock. Every animal, whether they looked sick or not. We used ivermectin because it was what was available and what most people told us to use. We dewormed on a schedule because that felt like the responsible thing to do. Treat the whole group, stay ahead of the problem, keep everyone clean.
That approach felt like good management. It was not. It was one of the worst things we could have done, and the research behind why is something every sheep keeper needs to understand before they ever pick up a dewormer.
When you treat every animal in the flock with a dewormer, you kill most of the worms in most of the animals. But the worms that survive are the ones with natural resistance to that drug. Those resistant worms then breed with each other and pass that resistance to their offspring. With every round of blanket treatment, you are selecting harder and harder for drug-resistant worms until eventually you have a population that nothing you have on hand will touch.
Unrestrained use of dewormers has caused barber pole worm to develop resistance to all three classes of dewormers. Benzimidazoles, ivermectins, and levamisoles. In some parts of the country the resistance is so widespread that multiple drug classes fail simultaneously on the same farm.
We contributed to that problem on our own pasture. And then we paid for it.
What ivermectin does to your soil that nobody talks about
There is another piece of this story that took us longer to understand, and it goes beyond the sheep themselves.
When you give an animal ivermectin, the drug does not disappear inside the animal. It passes through the body and exits in the manure. That medicated manure lands on your pasture. And what lives in and processes manure on a healthy pasture is dung beetles, earthworms, and a complex community of soil organisms that are responsible for breaking down organic matter, cycling nutrients, and keeping the soil biology alive.
Ivermectin is toxic to those organisms.
Research has found that dung from ivermectin-treated animals can remain on the pasture without noticeable signs of degradation for up to 340 days, while dung from untreated animals is almost completely processed after 80 days. That is not a minor difference. That is manure sitting on top of your pasture for nearly a full year, blocking grass growth, creating foul patches, and doing nothing for your soil because the organisms that process it are dead or suppressed.
Studies have found that ivermectin residues cause profound short-term and long-term ecological effects, disrupting dung beetle populations, dung degradation processes, and soil properties and functions. Soil carbon, nitrogen, and phosphorous availability all decline in pastures where ivermectin is used heavily. These are the exact nutrients your pasture needs to be productive.
If you are trying to build a regenerative farm, blanket ivermectin use on pasture animals is working directly against that goal. Every time you treat the whole flock on a schedule and put them back on the pasture, you are depositing a chemical that kills the biology your soil depends on.
We were building a regenerative operation in our minds while undermining the soil biology with our deworming practices. It took losing the whole flock to make us reckon with that honestly.
What we should have done instead: FAMACHA and targeted treatment
The system that changes everything for sheep and goat keepers dealing with barber pole worm is called FAMACHA. It was developed in South Africa in response to the exact drug resistance crisis that is now widespread in the United States, and it is one of the most practical tools available to a small flock owner.
Here is how it works.
Barber pole worm causes anemia because it drinks blood. Anemia shows up as paleness in the mucous membranes, specifically the inner lower eyelid of the sheep. A FAMACHA card is a color reference chart with five levels from bright red to nearly white. You check each animal individually by pulling down the lower eyelid and comparing the color to the card. Scores of one and two, bright pink to red, are healthy. A score of three is borderline. Scores of four and five indicate significant anemia and the animal needs treatment.
The key principle is this: you only deworm the animals that score three, four, or five. You leave the healthy animals untreated.
The reason this matters goes beyond saving dewormer costs. The worms in untreated animals, which are not drug-resistant worms since you have not selected for resistance in those animals, can interbreed with any resistant worms that survive treatment in the treated animals. That interbreeding dilutes the resistance in the worm population. It is called creating refugia and it is the mechanism that slows resistance development on your farm.
When you blanket treat the whole flock, the only worms left to breed are the resistant ones. When you treat selectively, you maintain a population of non-resistant worms that keeps the resistant genetics from taking over.
The practical result is that your dewormers keep working longer. And your healthiest animals, the ones with natural resistance to parasites, never needed chemical help anyway.
Culling: the part most beginners are not willing to do
This is the section that matters most and the one people most want to skip past.
Fifteen percent of the animals in a flock carry fifty percent of the worms. Twenty to thirty percent carry seventy to eighty percent of the worms. That is not a figure from one study. It is a consistent finding across sheep operations and it has a very clear implication: a small number of susceptible animals is contaminating your pasture and infecting the rest of your flock at a disproportionate rate.
FAMACHA scoring over time identifies those animals. The sheep that always scores a four or five, that always needs treatment while others in the same pasture eating the same hay score a one or two without any chemical help at all, is telling you something important about its genetics.
That animal is a parasite carrier. It is shedding millions of worm eggs onto your pasture every day. And parasite susceptibility is moderately heritable, which means if that animal reproduces, its offspring are more likely to have the same problem.
The hard truth is that culling those animals, removing the most susceptible individuals from the breeding population, is one of the most powerful tools you have for improving your flock's long-term parasite resistance. It is also one of the most emotionally difficult things to do when you are attached to the animal.
We were not willing to cull aggressively when we should have been. We treated instead. And we kept treating the same susceptible animals season after season while they seeded our pasture with billions of worm eggs and their genetics into our lamb crop. By the time we understood what was happening, the worm population on our pasture was out of control and the drug resistance we had built up through blanket treatment meant we had very little left to fight it with.
Rotational grazing as part of the solution
Parasite management and pasture management are not separate topics. They are the same topic.
Barber pole worm larvae hatch from eggs on the pasture and climb up grass blades to a height where they can be ingested by grazing animals. They cannot climb higher than a few inches. They also cannot survive indefinitely on the pasture without a host. If you move animals off a pasture section and give it time to rest before returning, a significant portion of the larvae die before the animals come back.
Rotational grazing systems that move animals through multiple paddocks on a regular schedule naturally reduce the parasite burden on any given section. Animals graze the section, move to the next one, and by the time they return the larval population has declined. Grazing cattle or horses in rotation with sheep also helps because cattle and horses are not susceptible to barber pole worm. They consume larvae without being harmed by them, reducing the population without getting sick.
This is the regenerative approach to parasite management. You work with the biology of the system rather than reaching for chemicals every time the problem appears. You use rotational grazing to break the lifecycle. You use FAMACHA to identify which animals truly need treatment. You cull the ones with no natural resistance. And you use dewormers sparingly and strategically when they are genuinely needed, which protects their effectiveness for when you really need them.
That approach builds a flock over time that is genuinely more resistant. It builds a pasture that is biologically healthier. And it reduces your dependence on chemicals that are working against both your animals and your soil.
What we would do differently if we started again
We would start with fewer animals and better genetics. Not the cheapest sheep available but animals from a producer who tracks FAMACHA scores and selects breeding stock based on parasite resistance. Buying resistant genetics from the start is the single highest-leverage thing a beginning sheep keeper can do.
We would set up a rotational grazing system before the animals arrived rather than after. Two or three paddocks with the ability to rotate weekly in parasite season is enough to make a meaningful difference.
We would learn FAMACHA scoring before we brought home the first animal. It takes thirty minutes to learn and it costs nothing. There are videos, extension resources, and local workshops available in most states through agricultural extension programs.
We would deworm only animals that scored a three or above, treat individual animals rather than the whole flock, and cull aggressively any animal that needed treatment repeatedly while others in the same conditions did not.
And we would think of our pasture soil as part of the livestock management system, not a backdrop to it. Every chemical that goes through our animals lands on that soil. Every practice we choose either builds the biology underneath us or diminishes it. A regenerative farm cannot be built on soil that has been sterilized by the byproducts of chemical dependence.
We know that now. We learned it the hard way. You do not have to.
One thing to do today
If you have sheep or goats or are planning to get them, search for a FAMACHA certification workshop in your state. They are typically offered through agricultural extension offices and veterinary schools and they take only a few hours. Getting certified is the first step to managing your flock the right way from day one rather than repeating the mistakes we made.
Until next Tuesday,
Tim Parker
Start My Homestead
Most homesteaders learn by repeated mistakes. We are here to help reduce the cost of those mistakes.
P.S. We lost ten sheep and a year of work to something that was largely preventable. If this letter saves even one flock it was worth writing. Share it with anyone you know who is keeping or planning to keep sheep or goats.
