Sudden Death Syndrome

Commonly associated with broiler systems

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Poultry Diseases

Sudden Death Syndrome

Also known as: Acute Death Syndrome, Flip Over

Intensive hens

There are no apparent clinical signs for sudden death syndrome until a minute before death

Sudden Death Syndrome is a condition associated mainly with commercial broiler systems, where apparently healthy birds suddenly die for no apparent cause. It tends to occur from 72 hours post-hatching up to 12 weeks of age, with the greatest losses occurring between 2 and 3 weeks.

The condition is also referred to as flip-over, acute death syndrome (ADS), dead in good condition, heart attack or lung oedema. It is associated with fast-growing broiler birds and it therefore should not be a problem in organic and extensive free range systems that use breeds suited to these conditions.

There are no clinical signs or unusual behaviour until less than a minute before death. Then there may be a sudden squawking, loss of balance, convulsions and frantic wing flapping. Birds tend to die on their backs (hence the term “flip-over”), with one or both legs raised.

At post-mortem birds show an enlarged, pale liver and kidneys may be pale and lungs congested and edamatous, although the latter may be a postmortem artifact.

It has been shown that in medium to fast growing breed-types, high specification rations tended to increase the incidences of ‘flip overs’ and leg culls.

In systems whereby birds are fed for slow growth this condition should not be a problem. An overview of the problem has been provided by Siddiqui et al (2009), identifying a number of factors that can influence incidence. Management factors that cause stress, such as high intensity light, high stocking rate and absence of exercise may induce or contribute to the condition. It has been suggested that bright sunlight may be a predisposing factor. Apart from the provision of shade, little can be done to protect free-range birds from intense sunlight.

A number of nutritional factors have been implicated, including diet texture, in that feeding pelleted feed can result in high growth rates and increased risk of SDS (Proudfoot and Hulan, 1982). Diets high in glucose as opposed to high starch have also been implicated.

Control and Prevention of Sudden Death Syndrome

Lowering carbohydrate energy intake by changing feed texture (mash) or density, or management methods such as feed restriction or long dark periods have been suggested to reduce deaths in broilers. A higher incidence has been noted in flocks fed wheat-based diets compared with those on maize diets.

The preventive measures outlined below have been extracted from work completed on high growth rate broilers and these measures should not be necessary in lower input systems with lower daily gains.

Whilst there are no proper treatment and preventive measures for control of SDS, Siddiqui et al (2009) outline the following prevention strategies:

  • Introduce management techniques that reduce early maximum potential for growth.
  • Use diets with 5-7% reduction in nutrient density
  • Supplement feeds with potassium salts
  • Supplement wheat-soya diets with sunflower oil
  • Dietary fat restriction from 0-7 days
  • Lowering the energy : protein ratio of finishing diets
  • Restricting feed of ad lib fed flocks by 30-40% (Bowes et al., 1988)
  • Feed a low protein/ low energy diet during first 14 days

Treatment of Sudden Death Syndrome

Given that this is a sudden death syndrome, treatment is not normally an option.

Good Practice based on Current Knowledge

  • Use breeds/strains that have not been selected for rapid growth
  • Provide shade so that birds can avoid bright sunlight
  • Do not use a high energy diet

Sudden Death Syndrome References


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  • Livestock should be land-based and integrated with farm cropping enterprises
  • Animals should be provided with conditions that enable them to exhibit natural behaviours
  • Dependency on veterinary medicines should be reduced without jeopardising the well-being of animals


outdoor access

Animals having outdoor access, shade, shelter, lighting and sufficient space for them to undertake free movement and to exhibit natural behaviors.


Using breeds and strains well-suited and adapted to the prevailing conditions.

Health Plan

Implementing herd and flock planning based on sound ecological practices and epidemiological knowledge.


Undertaking good practice with regard to biosecurity.

closed herds

Maintaining animals in closed herds and flocks and at stocking rates that enables free-movement, reduces risks of disease spread and minimises environmental damage.

forage and grazing

Forage and grazing being the main source of nutrients for ruminants, and continuously available to non-ruminants.

production practices

Avoiding the use of mutilations as standard production practices.


Improved understanding and responsible usage of veterinary medicines.