In a two-factorial experiment, 420 1-day-old male commercial broiler chickens were randomly divided and fed a basal diet with or without vitamin C (500 parts/10(6)). Half of the birds within each group receiving the same kind of feed were fed a T(3 )supplemented diet from day 1, in order to increase the ascites incidence. Weekly body weight and feed intake were measured. Venous blood samples were taken from 10 birds per group weekly from day 14 on, for haematocrit measurements, blood gas analysis, measurement of thyroid hormones and lactate/pyruvate ratios. Ascites mortality was recorded daily. Dietary T(3) significantly increased ascites mortality. Adding vitamin C to the feed significantly reduced ascites mortality while it had no effect on performance parameters. Plasma thyroid hormone levels were significantly reduced by dietary vitamin C administration, but neither haematocrit nor blood gas levels were influenced.

SUMMARYThe present study was designed to investigate the myocardial ß-adrenergic receptor characteristics in T3-induced ascites in two genetic lines of broilers, in order to look for possible involvement of myocardial ß-adrenergic receptors in the development of broiler ascites syndrome. Myocardial membrane fractions were prepared from 6 and 8 week old chickens fed a 1.5 parts/10 6 T 3 supplemented diet from day 1 in order to increase ascites incidence. Also, a similar assay was performed on myocardial cells of ascites sensitive and ascites resistant chickens at 5 weeks of age. The binding capacity and binding affinity of the myocardial ß-adrenergic receptor of the two genetic lines of birds did not differ significantly, but the tendency of ß-adrenergic receptor binding capacity and affinity constants in ascites-sensitive birds was slightly higher compared to ascites-resistant birds. In commercial broilers, although dietary T 3 significantly increased ascites mortality and the RV/TV ratio compared to control, it did not affect significantly ß-adrenergic receptor characteristics.