Ascites syndrome in broilers: physiological and nutritional perspectives.

Broiler chickens are intensively selected for productive traits. The management of these highly productive animals must be optimal to allow their full genetic potential to be expressed. If this is not done, inefficient production and several metabolic diseases such as ascites become apparent. The causes of the ascites are multifactorial but diet and, particularly, interactions between diet, other environmental and genetic factors play an important role. The relatively high heritability estimates for ascites-related traits and the significance of maternal genetic effects for most of the traits indicate that direct and maternal genetic effects play an important role in development of the ascites syndrome. An imbalance between oxygen supply and the oxygen required to sustain rapid growth rates and high food efficiencies causes ascites in broiler chickens. Because of the relationship to oxygen demand, ascites is affected and/or precipitated by factors such as growth rate, altitude (hypoxia) and environmental temperature. As the high metabolic rate (fast growth) is a major factor contributing to the susceptibility of broilers to ascites, early-age feed or nutrient restriction (qualitative or quantitative) or light restriction in order to slow down the growth rate seem practically viable methods, since final body weight is not compromised. Manipulation of the diet composition and/or feed allocation system can have a major effect on the incidence of ascites. Optimization of the house temperature and ventilation in cold weather seem helpful practices to decrease ascites incidence.