DIFFERENT CHARACTERISTICS IN CHICK-EMBRYOS OF 2 BROILER LINES DIFFERING IN SUSCEPTIBILITY TO ASCITES

1. The relationship between the length of incubation, hatching, hypoxi c condition, thyroid hormones and the occurrence of ascites were studi ed in embryos of 2 broiler lines differing in susceptibility to the as cites syndrome. 2. Both the time of external pipping (ep) and hatching of embryos from the ascites-resistant (AR) broiler line was earlier c ompared to the ascites-sensitive line (AS). The interval between inter nal pipping (ip) and ep was the same between the lines, but the interv al between ep and hatching was shorter in the resistant line. 3. The T -3 and T-4 concentrations in plasma of the AS line were lower compared to the AR line. 4. Analyses of partial pressures of oxygen (pO(2)) an d carbon dioxide (pCO(2)) in the air cell of the egg revealed that at day 18 the AS embryos had lower pO(2) and higher pCO(2) concentrations compared to the AR embryos. 5. The delay in hatching of the AS embryo s might induce a more pronounced and/or extended hypoxic environment, thereby creating an environment that evokes ascites.