(Sudden death syndrome, Heart attack, Acute death syndrome, Fatal syncope, Lung edema, Lung congestion, Dead in good condition)
Flip-over disease has been reported in most areas of the world that intensively raise broilers. Young, healthy, fast-growing broiler chickens die suddenly with a short, terminal, wing-beating convulsion. Many affected broilers just “flip-over” and die on their backs; 60-80% are males. The condition is uncommon or unrecognized when low-density feed is used and the ratio of feed intake to weight gain is >2.5 at 6 wk, or when broilers take 8 wk to reach 2 kg.
Etiology and Epidemiology: The cause is unknown but probably is a metabolic disease related to carbohydrate metabolism, cell membrane integrity, and intracellular electrolyte balance. Death likely results from ventricular fibrillation. The modern broiler tends to overeat and continues to grow rapidly while maintaining a low feed-to-gain ratio. Flip-over appears to be related to high carbohydrate intake. It is not known whether a genetic predisposition exists.
Incidence has been increasing since the condition was first recognized, likely at least in part because of continuing improved growth rate of ~5% in broilers. Mortality may now average 2% in North America; in some all-male flocks, mortality is >4%. In flocks with good management and disease control, it may be the most important cause of death, responsible for up to 70% of the flock mortality.
Clinical Findings: Broilers show no premonitory signs. They appear healthy and may be feeding, sparring, walking, or resting, but suddenly extend their necks, gasp or squawk, and die rapidly with a short period of wing beating and leg movement, during which they frequently flip onto their backs. They also may be found dead on their sides or breasts.
Flip-over may occur as early as day 3 and may continue until 10-12 wk in roaster flocks. The time of peak mortality varies but usually is between days 12 and 28, although it can be as early as day 9. It may occur after day 28, particularly if growth is restricted in young broilers. Mortality of 0.25%-0.5% per day can occur for 1-3 days.
Lesions: Confirmation is difficult because no specific gross or histological lesions are present. Dead birds are well fleshed, have an empty or partially filled crop containing normal ingesta, and feed in the gizzard. The abdomen is distended because the bird is fat and because the intestines are dilated and filled with semisolid digesta and mucus (as in any broiler that dies with the intestine full of feed). There is no evidence of stasis. The muscles are mottled red and white with congestion of the dependent muscles. Organs are moderately to severely congested. There may be small hemorrhages in the liver and kidney. The ventricles of the heart are contracted (but not hypertrophied), and the atria are dilated and blood filled. (If autolysis is advanced, the ventricles may be dilated.) The lungs are congested and frequently edematous; however, pulmonary edema increases with time after death and is not prominent in broilers that are examined within a few minutes after death. The gallbladder may be small or empty (as it is in many broilers on full feed).
Diagnosis: Good broilers found dead on their backs may be assumed to have died of flip-over because that position is rare in death from other causes except cardiac tamponade, asphyxia, and ascites syndrome ( Ascites Syndrome). Good birds on their sides or breasts, scattered in a random fashion in the pen also usually are considered to be dead from flip-over. Diagnosis is supported by the full GI tract (particularly the full intestine); the large, pale liver; the large, normal bursa; the contracted ventricles and dilated, blood-filled atria; the lung congestion and edema; and the lack of pathological lesions.
The condition called sudden death syndrome in Australia in broiler breeders coming into production is a different disease; it is reported to be caused by potassium deficiency. Similar mortality caused by a combination of high environmental temperature and hypophosphatemia or by acute hypocalcemia has been reported in North America.
Sudden death in turkeys can be caused by choke, aortic rupture ( Dissecting Aneurysm), focal
(obstructive) granulomatous pneumonia, or by hypertrophic
cardiomyopathy ( Round Heart Disease Of Turkeys)
with lung congestion and edema, splenomegaly, and perirenal
hemorrhage ( Perirenal Hemorrhage Syndrome Of Turkeys:
Prevention and Control: Activity caused by bright light (particularly sunlight), noise, and other disturbances may increase the incidence. After the first 3-4 days, low-intensity or low-intensity intermittent lighting should be used, and broilers should be disturbed as little as possible. Long, dark periods (18 hr dark for 3-4 wk) after the first 3-4 days reduce flip-over. Slowing growth rate by feeding a less dense or lower protein ration or by reducing feed intake by 15-20% may prevent the condition but does not appear to have a cost-benefit justification.