The use of blood gas parameters to predict ascites susceptibility in juvenile broilers

Ascites syndrome is a metabolic disorder found in modern broilers that have insufficient pulmo- nary vascular capacity. Commercial breeding programs have heavily focused on high growth rate, which led to fast-growing chickens, but as a negative consequence, the incidence of ascites syndrome increased. However, not all birds with a high growth rate will suffer from ascites syndrome, which might indicate a genetic sus- ceptibility to ascites. Information on blood gas param- eters measured early in life and their relation to ascites susceptibility is expected to contribute to identification on the cause of ascites syndrome. In this study, several physiological parameters, such as blood gas parameters (pH, partial pressure of CO2 in venous blood (pvCO2), and partial pressure of O2 in venous blood), hematocrit, electrolytes (Na + , Ca 2+ , and K + ), metabolites (lactate and glucose), were measured at d 11 to 12 of age from 100 female and 100 male broilers. From d 14 onward, the birds were challenged to provoke the development of ascites syndrome. Our results showed that high pvCO 2 values together with low pH values (males) or high pH values (females) in the venous blood of juvenile broilers coincided with ascites. Therefore, blood pvCO 2 and pH in both juvenile male and female broilers seem to be critical factors in ascites pathophysiology and can be used as phenotypic traits to predict ascites susceptibil- ity in juvenile broilers at d 11 to 12. A prediction model was built on a subpopulation of the broilers without any loss in sensitivity (0.52) and specificity (0.78) when applied to the validation population. The parameter sex was included in the prediction model because levels of pvCO2 and pH that associated with ascites suscep- tibility are different between males and females. Com- mercial breeders can include these phenotypic traits in their genetic selection programs to reduce the incidence of ascites syndrome.