RESUMEN
Increasing of oxygen consumption in fast growing broiler chickens is associated with the more pronounced occurrence of right ventricular hypertrophy and ascites. While, rearing of susceptible chickens in dark condition could reduce the metabolic rate of birds and hence the incidence of ascites. The present study was designed to investigate a comparative study on the influence of different dark-length schedules on the incidence of ascites and metabolic parameters in fast growing broiler chickens. A total of 1000 day-old [Pure Sir Broiler Line Arian] chickens were obtained and subjected to four different lighting programs. Dead birds were autopsied for the lesions of ascites. Weekly growth performance of chickens was determined and blood samples were taken, on days 7, 12, 21, 28, 35 and 42 of age for hormonal analysis. The incidence of ascites was clearly higher in birds subjected to normal lighting program compared with those of dark exposed chickens. Control chickens showed significantly higher body weight compared to the dark exposure group birds at day 21 of age, while it did not differ at days 28, 35 and 42 of age. Such differences was accompanied with the lower levels of plasma T3 and T4 concentrations in dark group chickens than to control chickens at the earlier age [days 12 and 21]. This phenomenon indicated a reduction of metabolic rate and oxygen consumption in dark group chickens that had been led to reducing of ascites incidence. Our data proves that increasing dark-length instead of continuous lighting may be beneficial for rearing of broiler chickens, especially, when the risk of ascites incidence is higher
RESUMEN
The present study was designed to examine the anatomical parameters of the cardiopulmonary system, the function of venous blood gas parameters and the development of ascites incidence in two genetic line chickens. Three hundred forty day-old chickens from two pure broiler breeder lines, which were different in their growth rate and susceptibility to ascites syndrome were obtained. The relative heart an lung weights, the volumes of the heart, lung and thorax cavity, the incidence of ascites, and the venous blood gas parameters in these two genetic line chickens were followed. In the present study, the incidence of ascites and right ventricular hypertrophy was markedly higher in the fast-growing broiler chickens compared to the slow-growing chickens, as two genetic line chickens exhibited significant differences in their growth performance traits. The volumes of the thorax cavity, before and after removing the heart and lung tissues, were lower in fast-growing broiler chickens compared to the slow-growing chickens. The relative lung volume was significantly lower in the fast growth chickens than the slow growth chickens at the earlier age, but it did not differ at the later age. Additionally, a rise in carbon dioxide tension and a decline in oxygen pressure in the venous blood of rapid growth compared to the slow growth broiler chickens were observed. It could be concluded that there is an association between the insufficiencies of the cardiopulmonary system with the function of the venous blood gas parameters and the development of ascites syndrome in fast growing broiler chickens