Sudden Death or Flip-Over Syndrome in Broilers

A farmer at Awutu Breku called us on the 19th day of his batch, upset. He had walked into the house at 6 am and found nine broilers dead, all lying on their backs with their legs in the air, all among the biggest in the flock, all of them birds he had watched eating with enthusiasm the evening before. There was no discharge, no diarrhoea, no swelling, nothing. The rest of the flock was eating as if nothing had happened. He had already dosed the water with an antibiotic and a "flu remedy" bought that morning, and he wanted to know what disease could kill a healthy bird overnight without a single sign.

The answer is that it was not a disease, at least not in the sense he meant. What he described is sudden death syndrome, known in the trade as flip-over, acute death syndrome, or simply "dead on back". It is a metabolic collapse, a fatal heart rhythm disturbance in a broiler that has been growing at full speed, and it kills in under a minute. The bird is eating or walking, it gives a short convulsive flap of the wings, it falls onto its side or back, and it is dead. Farmers who happen to be in the house at the time describe it as a fit or a heart attack, and that is close enough.

This guide is about what happens in those final seconds, why the fastest-growing birds are the ones that die, how to tell flip-over from the infectious diseases it is confused with, and which management changes reduce it. Like its cousin ascites, it cannot be treated in an affected bird, so the work is all upstream. We have written a separate guide on ascites or water belly; the two share causes but they look and behave differently on the farm.

What sudden death syndrome is

Sudden death syndrome (SDS) is an acute cardiac event in fast-growing broilers. The precise trigger is still debated, but the accepted picture is a ventricular arrhythmia, a chaotic electrical rhythm in the heart muscle, in a bird whose heart is under strain from rapid growth, high metabolic rate and a large meal. The heart stops pumping effectively, the brain loses oxygen, the bird convulses briefly and dies. Post-mortem shows almost nothing, which is the diagnostic clue: a bird in excellent condition, a full crop and gut, a heart that may be slightly enlarged or contracted, congested lungs, and no lesions of any infectious disease.

It is seen almost exclusively in broilers, rarely in layers or local birds, and overwhelmingly in the fastest-growing individuals of a flock. Males are affected about twice to three times as often as females because they grow faster. The peak age is two to four weeks, earlier than ascites, and cases continue at a lower rate to market age. Under intensive conditions it accounts for anywhere from 0.5 to 4 percent of a flock, which makes it, together with ascites, one of the two most important non-infectious causes of broiler mortality in the world.

The link to feeding is strong. Birds tend to die within an hour or two of a large meal, most often in the morning after the lights come on and the flock rushes to the feeders, or in the late afternoon. Anything that concentrates feeding into a short, frantic period increases the risk. Anything that causes a sudden fright to a flock with full crops, a dog in the house, a door slamming, a worker running, can trigger a cluster. We have had farmers report five or six flip-over deaths within minutes of a generator backfiring beside the house.

The signs: what you will find and what you will not

Recognising SDS is largely a matter of noticing what is absent. The bird was healthy. There was no lead-up. The signs listed below are the whole picture.

• Dead bird on its back, legs extended upward or stretched behind, wings often partly spread. Around 70–80 percent of SDS birds are found on their backs, the rest on their sides or breast; the convulsion before death flips them.
• Excellent body condition, one of the heaviest birds in the pen, well fleshed, full crop.
• No prior signs: eating, drinking and active until seconds before death. If you watch it happen, there is a loss of balance, a brief violent wing-flapping and leg-paddling lasting a few seconds to a minute, then stillness.
• No discharge, no diarrhoea, no swelling, no lameness, no respiratory noise.
• Deaths spread across the house, one here and one there, not clustered in a corner (which suggests smothering) or near a heat source.
• Mortality of one to a few birds a day, not the escalating pile that marks an outbreak.

Ruling out the diseases that also kill suddenly

Because SDS is diagnosed partly by what is missing, it is dangerous to assume every dead-on-back bird is flip-over. Several infectious diseases kill quickly, and misreading them as a metabolic problem delays the response. The table sets out what to look for.

A field screen, not a diagnosis. If deaths are rising day on day, involve small birds as well as large, or come with nervous or respiratory signs, call a veterinarian the same day, and report suspected Newcastle disease or avian influenza to the Veterinary Services Directorate immediately.

The practical rule we give farmers: if you find dead birds on their backs and every one of them is a big, healthy-looking bird, and the count is stable at one to three a day, it is almost certainly SDS. If the count is climbing, if small or thin birds are dying too, or if any live bird is showing signs, it is not, and you need a vet. Our guides on Newcastle disease and why chicks die cover the infectious side.

Why the best birds die

SDS is a disease of success. A Cobb 500 or Ross 308 male at 21 days weighs close to a kilogram, five to six times its hatch weight. Its heart has grown, but not proportionally, and its metabolic rate is extraordinary: the bird is essentially running flat out all day, every day. Several factors are consistently associated with higher rates.

• Rapid growth in the first three weeks. The faster a flock reaches 1 kg, the more SDS it has. Flocks deliberately held back in weeks one to three have markedly less.
• Continuous light. Twenty-four hours of light means twenty-four hours of eating and activity. Birds on continuous light have higher SDS than birds given a dark period, and this is the single most repeatable finding.
• Pelleted, high-energy feed. Pellets are eaten faster and in larger meals than mash, and feeds high in fat and energy raise metabolic rate. High-carbohydrate meals in particular are associated with the arrhythmia.
• Large, infrequent meals. Feeders that run empty and are then refilled cause a frantic rush and overfilled crops. Feed that is always available in small, steady amounts is safer.
• Stress and excitement. Sudden noise, chasing, catching for weighing, a dog or a hawk, and the rush at lights-on all trigger clusters.
• Heat. Hot afternoons add cardiac load; SDS rises in the hot months and in poorly ventilated houses.

Lighting: the most effective single change

A dark period does three things. It stops the bird eating for several hours, so the crop empties and the arrhythmia trigger passes. It lowers metabolic rate and heart rate while the bird sleeps. And it slows growth slightly in the critical early weeks, which allows the heart to catch up with the body. Broiler companies have used lighting programmes for SDS and ascites control for decades, and small farms in Ghana can copy them with nothing more than a timer switch from any electrical shop. The dark block must be continuous and truly dark, with no security bulb left on, and lights should be dimmed down and up gradually so the flock settles rather than panics. Our lighting programme guide covers timers and bulb types.

Orientation programme for Cobb 500 and Ross 308 in open-sided houses in Ghana; the dark block should be at the coolest part of the night. Farms selling at heavier weights or in very hot weather may adjust; discuss with your veterinarian or breed supplier.

Feed: form, energy and timing

Feeding for SDS control is not about feeding less. It is about avoiding surges. The bird should be able to eat a little, often, rather than a lot, occasionally.

• Never let feeders run empty and then refill. This produces the rush and the overfilled crop that precedes a flip-over cluster. Top up before they are empty, ideally with enough feeder space that every bird can eat at once (about 2.5 cm of trough per bird at three weeks, or one tube feeder per 30–40 birds).
• Mash or crumble in the first three weeks, not pellets. Farmers who feed pellets from day one for "faster growth" get exactly that, and SDS with it. Pellets can come in from week four when the risk falls.
• Do not boost the starter with oil or fat. A starter at 22–23 percent protein and about 2,950–3,000 kcal per kg is enough. Adding palm oil to make the birds "shine" adds energy the heart does not need in week two.
• Delay finisher. Move to grower at day 21–24 and finisher at day 28–30, not earlier.
• Check the salt and mineral premix. If you mix your own feed, be exact with salt and use a reputable broiler premix that supplies potassium, magnesium and biotin. Our broiler feeding guide and phase feeding guide set out the rates.

What to do this week if you are losing birds now

If you are at day 18 and finding two or three flip-over birds a morning, here is the sequence for the next few days. It will not save the birds already predisposed, but it will reduce the count within about a week.

1. Confirm it. Open two dead birds. Full crop, no fluid, no lesions, heart normal: SDS. Anything else, or rising numbers, means a veterinarian today.
2. Introduce a dark period tonight. Six hours, continuous, at the coolest part of the night. Dim gradually.
3. Stop the morning rush. Fill feeders before lights-on so there is feed everywhere when the birds wake. Add feeders if birds are queuing.
4. Step back the feed. If you are on pellets or an early finisher, go back to crumble or grower for two weeks.
5. Add electrolytes with potassium and vitamins to the water for a week, especially if it is hot. Ask your vet or agro shop for a broiler electrolyte rather than a generic "anti-stress".
6. Calm the house. No catching, no weighing, no visitors, no dogs, no noise for a week; enter slowly and speak before opening the door. Hawks and other predators send a flock with full crops into a panic, so keep them out.
7. Stop the antibiotics unless a vet has diagnosed something that needs them. They are doing nothing for SDS and they add a withdrawal period before you can sell.

A mini-case: 800 Ross 308, all-night light, day 17

A farmer at Kasoa Millennium City placed 800 Ross 308 chicks from us in March 2025. His house had four bulbs on all night because he believed the birds "should never stop eating", he fed pellets from day 10 bought as a "fast finisher", and his single worker refilled the two tube feeders per pen only when they were empty, twice a day. He lost his first two flip-over birds on day 15, then three or four a day from day 17. By day 24 he had lost 43 birds, every one a large male on its back, and had bought two courses of antibiotics and a bottle of something labelled for "heart and lung" that cost more than a bag of feed.

We visited, opened three birds with him and showed him the full crops and clean organs. That evening he switched three of the four bulbs off at 10 pm and the last at 10:15, back on at 4:30 am. He went back to crumble for two weeks, added two more feeders per pen, and told his worker to top up feeders at 4 am before the lights, at noon and at 6 pm. He stopped all medication. Losses fell to one a day within four days and to none by day 32. He sold 731 birds at day 40 at an average of 2.15 kg. His next batch, run on the same programme from day one, lost 21 birds in total, of which perhaps five were flip-over. The timer switch cost GH₵ 60.

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