Ascites syndrome in poultry: a review

Excessive specialisation and production requirements place high demands on the metabolism of the broiler chicken. A number of metabolic problems, such as ascites, arise in chickens due to intensive selection to manifest their genetic potential for rapid growth. Ascites syndrome (Pulmonary Hypertension Syndrome) is one of the major causes of mortality and morbidity in modern broiler production today. Genetics, the environment, and management all seem to interact to produce a cascade of events that culminate in ascites syndrome. It is generally accepted that the high metabolic rate of current broiler lines causes an increased demand for oxygen, especially in cold environments or when birds are fed high nutrient density diets. In such situations, the relatively underdeveloped cardio-respiratory system of modern broilers fails to fulfil the required oxygen demand, which leads to hypoxemia, resulting in the development of pulmonary hypertension and subsequently ascites. Many nutritional, medicinal and management strategies have been proposed to alleviate the ascites. Higher levels of dietary vitamin C and E along with selenium might be beneficial, as they decrease the free radicals that are generated in birds with ascites. As the high metabolic rate (fast growth) is a major factor contributing to the susceptibility of broilers to ascites, appropriate selection strategies or feed restriction or light restriction in order to slow down the growth rate seem practically viable methods, since final body weight is not compromised. Optimisation of the house temperature and ventilation in cold weather seem helpful practices to decrease the incidence of ascites.