Short answer: Perosis is a hock problem in which the tendon slips out of its groove, leaving the joint swollen and the bird hopping or sitting on its hock. In young chicks and growers it is most often linked to too little manganese or choline in the ration, with biotin and a skewed calcium to phosphorus balance as other contributors. Fix the mineral and vitamin content of the feed and the floor under the birds, rather than cutting feed, which only sets the flock back.
Key takeaways
- Perosis is a tendon and hock problem that starts with a nutrient shortfall, most often manganese or choline, with biotin as another suspect.
- A swollen, thickened hock in a young bird is a feed question first and a growth question second.
- Cutting feed to slow growth is the wrong fix and often leaves the flock weaker.
- Slippery floors and high perches can turn a mild hock problem into a slipped tendon.
- An infected joint can look similar, so a hot or oozing hock needs a vet, not just a feed change.
A hock that looks like a knuckle
The first sign we hear about is usually a bird that sits down at the feeder with one leg stuck out to the side. A chick at two or three weeks old is pushing its feed around the trough from a sitting position, and when you lift it, the hock looks thick and rounded, like a knuckle knocked out of line.
Sometimes the bird hops on one leg while the other is held up. Sometimes it stands on the hock with the foot pushed forward. In every case the tendon on the back of the leg has slipped out of the groove it sits in, and the joint has begun to swell around it.
This is perosis, sometimes called slipped tendon. It is not the same thing as the leg trouble that turns up in the last fortnight of a heavy broiler cycle, which our skeletal problems guide covers. The birds here are chicks and growers that show it early. That early timing is the first clue that feed, and not weight alone, is behind it.
What the tendon is doing when it slips
The tendon that bends the foot runs down the back of the leg and passes over the hock. It sits in a groove on the bone, and the groove keeps it in line while the bird walks. When the bone and cartilage around the groove grow poorly, the groove becomes shallow or oddly shaped, and the tendon can ride off the edge with an ordinary step.
Once it has slipped, the tendon stretches and the joint fills with fluid and inflammation. The bird feels pain, avoids weight on that leg, and the muscles on that side waste. A slipped tendon caught early can sometimes be eased back, but most of the damage sits in the bone and cartilage underneath, and that is the part the feed has to fix.
This matters for a farmer because you cannot massage a whole brood's tendons back into place. You can only change what the birds grow with, and that means looking at the ration.
Manganese: the mineral that builds the joint
Manganese is a trace mineral, but the bird needs it in the right amount. It is part of the enzymes that make the molecules forming cartilage and bone matrix. When manganese is short, cartilage is not laid down properly, the long bones come out short and thick, and the hock and tendon groove develop poorly. The result is perosis.
The trap is phytate. Cereal bran, especially wheat bran and rice bran, carries phytate, a compound that binds minerals in the gut and makes them less available. A ration can look as though it has enough manganese on paper and still deliver too little to a chick. That is why we tell farmers the figure on the label is a target, and the bird's bones are the test.
A premix with a manganese figure stated on the label is the simplest protection. If you mix your own, do not assume bran and maize cover the mineral. Check the ingredient list and ask your feed supplier or your vet for a basic analysis.
Choline and biotin, the quieter suspects
Choline is needed to make the building blocks that cartilage and cell membranes depend on, and it works alongside methionine in the bird's chemistry. When choline is short, young birds develop perosis even when manganese is adequate. Choline chloride is the form used in most premixes, and it is one of the cheaper additions when a feed is formulated properly.
Biotin is the third suspect. It is needed for bone growth and for the skin of the feet. Biotin deficiency in chicks shows up as slipped tendons and rough, cracked foot pads, and in breeders it can lower hatchability. Biotin can lose activity in feeds that are heat-processed and stored a long time, so fresh feed helps.
A farmer does not need the chemistry to act on it. What matters is that a home mix built only from maize, bran, groundnut cake and a little salt is likely short on at least one of these. A complete starter feed with a proper vitamin and mineral premix closes the gap for most of the first six weeks.
Sorting perosis from the other leg problems in the brooder
A swollen hock is not the only leg problem a brooder can throw up. The other two that catch farmers out are curled toe paralysis, a riboflavin nerve problem, and spraddle leg, which is really about the floor. Each one looks different on the bird.
Perosis is a joint and tendon problem. The hock is thick, the tendon may sit out of its groove, and the bird favours one leg or sits on its hock. A curled-toe chick has curled toes and no joint swelling, and it walks on its hocks because the feet will not hold. A spraddled chick has legs splayed to the sides from its first days, because the floor gives it no grip to pull them under.
Look at the hock with the bird in your hand, not on the floor. Then look at the toes. Then look at the surface the bird has been standing on. That order saves a lot of guesswork, and the curled toe guide and the spraddle leg guide go deeper on the other two.
Fast growth and a lopsided calcium ratio make it worse
Perosis is a nutrition problem, but fast growth gives it a stage to act on. A chick on a high-energy starter that puts on weight quickly loads legs that have not yet built the joint. A chick that grows fast on a feed short of manganese is usually the one whose hock gives way first.
Calcium and phosphorus matter too. Too much calcium in a young bird's ration can interfere with the uptake of other minerals, and a poor calcium to phosphorus balance affects bone development. This is not a case for adding more calcium. It is a case for a balanced starter and for keeping any calcium source at the level the feed maker set.
The tempting response is to cut the feed. We understand the instinct: the bird is lame, the weight is high, and the farmer wants the bird to slow down. But restricting a young bird's feed does not fix a mineral gap. It stunts the brood and leaves it weaker against the next disease. Fix the balance, keep the feed steady, and let the bones catch up. Our guide to salt and minerals in feed explains the balance in more detail.
Surfaces that turn a mild hock into a slipped tendon
Once a hock has begun to swell, the floor decides how fast the tendon gives way. A chick that spends its days on smooth concrete or a plastic-coated surface has to push off on a slippery grip every time it moves, and each step strains the joint.
Wet litter builds up under drinkers and along the water line. The hock sits in that mess, and a bird with a sore joint is more likely to sit in the wet, which makes the swelling worse. Keep the litter dry around the drinkers, move drinkers so spill does not pool, and fix leaks the same day.
Perches are a problem in some houses. A chick on a bar that is too high, too thin or too round will slip and drop onto its hock. For young birds, keep perches low and wide, or leave them out until the chicks are stronger.
- Use dry, absorbent litter the chick can grip, not smooth paper or bare plastic.
- Keep the area around drinkers dry, and fix leaks the same day.
- Keep perches low and wide, or remove them for young chicks.
- Lift and check one or two birds a day for a swollen hock.
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Reading the feed label for the minerals that matter
The table sets out the main nutrients linked to perosis, what each one does, what a shortage looks like, and where it usually goes missing on a Ghanaian farm. Use it when you review a feed label or a home-mix recipe.
| Nutrient | What it does for the leg | What a shortage looks like | Where it goes missing |
|---|---|---|---|
| Manganese | Helps build cartilage and bone matrix | Short, thick long bones, slipped tendons, shortened legs | Bran-heavy home mixes, feeds without a mineral premix |
| Choline | Supports cell membranes and joint tissue | Perosis that appears even when manganese is adequate | Maize-based mixes with no choline source |
| Biotin | Needed for bone growth and foot skin | Slipped tendons, cracked foot pads, poor hatch in breeders | Heat-processed or long-stored feed |
| Calcium and phosphorus | Bone mineralisation | Weak, bendy or thickened bones | Shell or bone meal added in the wrong amount |
Use the table to point you at the first check, not to name the disease. Current chick prices are on our price page if you are planning a restock. A swollen hock might be a mineral gap, an infection, a bruise, or a mix of these. The point of the table is to make the feed the first place you look.
A worked example: 400 Kuroiler chicks on a bran-heavy mix
Take a farmer who started 400 Kuroiler chicks at GH₵11 each, which is GH₵4,400 before feed. The brood went onto a home mix built around wheat bran, maize and groundnut cake, with nothing added for minerals and no premix. The farmer had never written down the mineral content of anything in the bin.
Around week three the farmer began to see birds sitting on their hocks at the feeder. By the end of the week 24 birds, about 6 per cent of the brood, had visibly swollen hocks, and nine of them were struggling to reach the feed. A call to the vet and a few photographs on WhatsApp sorted out the next steps.
The fix was a complete grower feed whose label listed manganese and choline levels, switched the same day, and the floor under the drinkers was dried and raked. Within ten days no new swellings appeared. The vet sorted the 24 affected birds: 15 continued to grow and were sold, and the nine that could not reach feed were culled.
Nine birds at GH₵11 is GH₵99 in chick price. The larger cost was that the 24 affected birds ate feed without putting on weight at the normal rate, and the brood finished about four days late. Multiplied across feed, labour and house time, that delay cost more than the chicks did.
A brooder and feed-bin routine that prevents most cases
- Check the feed label or recipe for a manganese and choline figure before the first bag goes out.
- Use a complete starter for the first weeks rather than building a bran-heavy mix from scratch.
- Keep the litter dry and absorbent for the first three weeks, and clear wet patches every day.
- Lift and check a handful of chicks every second morning, looking at the hocks and the feet.
- Note any bird that favours one leg, and record its age and the house section.
- Do not change feed brand midway through a brood without a gradual switch.
Keep the routine short. A farmer who checks the hocks every day for three weeks catches most early cases, when a feed change still does some good. By the time a bird is sitting on its hock every morning, the damage is well under way.
When the hock is hot, swollen or oozing, call the vet
Perosis does not usually bring heat, pus or a bad smell to the joint. If the hock is hot, the bird looks feverish, the joint is oozing, or several birds limp on the same leg, you are probably looking at an infection rather than a nutrition problem. Bacteria can enter a joint through a scratch, and a joint infection can look like a slipped tendon from across the house.
Ask your vet to open a bird if the picture is unclear. The post-mortem shows whether the tendon has slipped, whether the joint holds fluid or pus, and how the bone growth looks. That answer decides whether you change the feed, change the house, or treat an infection. Our post-mortem guide explains what to look for when you open a bird yourself.
If you are restocking after a brood with leg problems, settle the breed and the feed plan first. Our Kuroiler and Noiler chick page sets out what those birds need. Describe the house, the age of the flock and the feed you use, and send it to +233 24 915 1503 on WhatsApp. The order form is there once you have decided on a breed.
Questions farmers ask
What causes perosis in young chicks?
Most often a shortfall of manganese or choline in the ration, with biotin as another possible factor. Fast growth, a poor calcium to phosphorus balance and slippery floors make it worse. It is a nutrition and management problem rather than something a chick catches from another bird, though an infected joint can look similar and needs different treatment.
Is slipped tendon in chicks the same as in broilers?
The mechanism is similar, but timing and cause differ. In broilers, slipped tendon usually appears in the heaviest birds near slaughter age and is tied to growth speed. In chicks and growers it appears earlier and is often linked to a mineral or vitamin shortfall in the feed.
Can a bird with perosis recover?
Mild cases can improve when the feed is corrected and the floor is dry, especially if the tendon has not fully slipped. Severe cases, where the tendon has stayed out of its groove for days, often keep a deformed joint. Judge each bird and ask your vet about culling birds that cannot reach feed or water.
Should I give extra calcium to help the bones?
Not without a formula. Too much calcium can block the uptake of other minerals, including manganese, and make the balance worse. Adding shell or bone meal by eye is a common way to tip a ration the wrong way. Keep to the calcium level your feed maker set for the bird's age, check the phosphorus too, and ask your vet if you are unsure what the bird is getting.
Will cutting feed slow the growth and stop the slipping?
It can slow growth, but it does not fix the mineral gap, and it can leave the brood weaker and more open to disease. A balanced ration held steady on a dry floor is the better approach. Speak to your vet if weight gain in a particular flock worries you.
Is a manganese supplement enough on its own?
Only if the rest of the ration is sound. Choline and biotin matter as well, and a single mineral added to a poor mix rarely fixes the joints on its own. A complete premix covers the set, which is why a single-ingredient fix often disappoints. Ask the maker for the full list of minerals and vitamins on the label, not just the one you have heard about.
How do I know the hock is perosis and not an infection?
Perosis rarely brings heat, pus or a foul smell to the joint. An infected hock is often hot, swollen with fluid and may be oozing. If you see those signs, call your vet and ask for a post-mortem rather than changing the feed alone.
