Interactive lesson

Parasites without synthetics, step by step

Interactive lesson: keep worms, liver fluke and ticks at low numbers — faecal egg counts, FAMACHA, rotational grazing and a wormer only when needed.

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The whole lesson as text

1. How parasites live on pasture

Every grazing animal has parasites; the trouble starts when their numbers shoot up.

Eggs in the dung — The animal passes eggs in its dung. In warmth and damp, a larva develops from the egg.
Larva on the grass — The larva climbs the grass, mostly up to 5 cm (2 in). Grazing below 8–10 cm (3–4 in) forces the animal to eat exactly there.
The cycle closes — The animal eats the larva with the grass. In 3–4 weeks the adult worm lays new eggs.
Fluke by the water — Liver fluke develops inside a small mud snail, and its larvae stick to grass near water. That's why it is tied to wet meadows, springs, ditches and puddles.

Why: Most worms of ruminants and horses share the same life cycle, and that is the key to control without chemicals. Warmth and damp speed up development: in the UK and Ireland the risk peaks from midsummer to autumn, and in the US South barber's pole worm is the main killer from spring to autumn.

Larvae on grass live for months. Resting a paddock cuts their numbers, but doesn't clean it completely.
Every new animal brings its own parasites, sometimes resistant to wormers. Hence quarantine and a faecal egg count before turnout.

2. Faecal egg counts

Don't treat blindly: a faecal egg count tells you whether there are parasites, which ones and how many.

Take fresh dung — Ideally straight after it is passed, or with a glove from the rectum. Old dung from the ground is no good.
Pooled sample — A pinch of dung from 5–10 animals of the same group in one bag, for example adult goats or kids. For a single animal: its own bag.
Label and tie — Write the group or animal, the date and the species on the bag. Squeeze out the air and tie it.
Fridge, 1–2 days — Keep it in the fridge, not the freezer, and take it to the lab or vet within 1–2 days. Record the result and the vet's advice.

Why: The lab counts worm eggs per gram of dung (EPG). What the number means for your animals is for the vet to judge, because it depends on the species, age and type of parasite.

Goats and sheep: spring, midsummer and autumn, young stock more often. Horses: 2–4 times a year.
After a wormer, ask the vet to repeat the count on the same animals 10–14 days later. If the egg count hasn't dropped, the parasites are resistant.