Ascites resistance of progeny from broiler breeders selected for two generations using chronic unilateral pulmonary artery occlusion

Broilers that survived unilateral pulmonary artery occlusion and lived to m aturity comprised the first generation (GEN1) of an ascites-resistant line. Progeny from the GEN1 line previously were shown to tolerate fast growth a nd cool temperatures with a 50% lower incidence of ascites than chicks from the breeder pullet line serving as the base population for the resistant l ine. In the present study, progeny from the GEN1 line were subjected to uni lateral pulmonary artery occlusion, and survivors were reared to breeding a ge to serve as the parent stock for the second generation (GEN2) ascites-re sistant line. In two experiments (EXP1 and 2), chicks were reared separatel y by sex but were mixed by line within environmental chambers, where they w ere grown as rapidly as possible and exposed to cool (14 C) temperatures fr om 17 to 49 d of age. In EXP1, the ascites incidences in the base populatio n, GEN1, and GEN2 lines, respectively, were 31% (48/157), 15% (8/52), and 4 % (3/69) for males and 10% (13/128), 11% (5/46), and 3% (1/36) for females. Ln EXP2, the ascites incidences in the base and GEN2 lines, respectively, were 44% (71/163) and 6% (7/110) for males and 12% (19/155) and 0% (0/92) f or females. The final BW for nonascitic broilers did not differ across line s in EXP1. In EXP2, the final BW was Lighter for nonascitic GEN2 males (2,9 15 +/- 43 g) and females (2,382 +/- 17 g) than for nonascitic base populati on males (3,088 +/- 42 g) and females (2,493 +/- 22), respectively. Right t otal ventricular weight ratios were higher for ascitic than nonascitic broi lers, confirming the primary role for pulmonary hypertension in the pathoge nesis of ascites. These experiments demonstrate ongoing improvement in the ascites resistance of progeny from broiler breeders that, for two consecuti ve generations, have survived the rigorous selection pressure imposed by un ilateral pulmonary artery occlusion.