The present study was designed to investigate the effect of different atmospheric pressure on the endogenous functions of broiler chickens during embryonic, hatching and growing periods related to ascites. Eggs from a commercial broiler line were incubated in two similar commercial incubators at high and low altitudes. The effect on embryonic development and physiological functions including hatching parameters, incidence of ascites and growth performance were examined. Embryos incubated at high altitude had higher plasma triiodothyronine, thyroxine, corticosteroid and lactic acid levels, and hatched earlier than those incubated at low altitude. Embryonic mortality was higher at high altitude. Chickens that had been incubated at high altitude showed less right ventricular hypertrophy and ascites mortality than those incubated at low altitude. It was concluded that different atmospheric pressure during incubation interacts with the endocrine functions of the embryo and hence affects hatching parameters, thereby influencing ascites susceptibility.

The effects of dietary garlic bulb were studied separately on hematological parameters, ascites incidence, and growth performance of an ascites susceptible broiler hybrid under both standard temperature conditions ( STC: ) and cold temperature conditions ( CTC: ). A total of 336 one-day-old male broiler chickens were allocated to 4 experimental groups with 4 replicates of 21 birds each under STC. In addition, the same grouping with another 336 birds was used for CTC. Under CTC, the birds were exposed to cold temperatures for induction of ascites. Experimental groups were defined by the inclusion of 0 (control), 5, 10 or 15 g/kg garlic bulbs in the diets under both STC and CTC. Growth performance, systolic blood pressure (as a measure of systemic arterial blood pressure), physiological and biochemical parameters, as well as ascites indices (right ventricle [ RV: ], total ventricle [ TV: ] weights, and RV/TV: ) were evaluated. Systolic blood pressure was determined using an indirect method with a sphygmomanometer, a pediatric cuff, and a Doppler device. The final body weight decreased quadratically (P = 0.003), with increasing garlic bulb levels in the diets under STC. The feed conversion ratio showed no significant differences among all groups under both STC and CTC. No significant differences were observed in total mortality and ascites-related mortality in all groups under STC, although total mortality (L: P = 0.01; Q: P = 0.001) and ascites-related mortality (L: P = 0.007; Q: P = 0.001) were significantly different among the diets under CTC. Under STC, the systolic blood pressure, packed cell volume, hemoglobin, RV, TV, and RV/TV did not vary significantly among the diets. However, red blood cell count and erythrocyte osmotic fragility decreased linearly (P < 0.005) with increasing garlic bulb levels in the diets under STC. Under CTC, the systolic blood pressure, packed cell volume, red blood cell count, and erythrocyte osmotic fragility decreased (P < 0.05) with increasing garlic levels. It is concluded that the inclusion of 5 g/kg garlic bulb in susceptible broiler chicken diets has a systemic anti-hypertensive effect and could decrease ascites incidence without impairing broiler chicken performance.

The influence of an intermittent lighting programme during the 12h of the dark period on the incidence of ascites and on metabolic parameters of broiler chickens was examined. A group of 336 1-day-old male broiler chickens were randomly allocated to two open rooms At 5 days of age, an intermittent lighting schedule of 3h of dark alternating with 1h of light was introduced during the night in one room, while in the second room the schedule consisted of 23 h of light alternating with 1 h of dark. One-half of the birds in each room were fed a diet supplemented with 1.5ppm 3, 3', 5-triiodothyronine (T(3)), while the other half received a control diet. Mortality associated with ascites was significantly higher in birds fed the T 3 -supplemented diet, but was significantly lower in birds in the room receiving the intermittent lighting schedule. The intermittent lighting programme was also associated with a temporary reduction in growth rate, packed cell volume and plasma T(3) concentrations, suggesting reduced oxygen utilization. However, final body weights were not significantly affected by the lighting programme. It was concluded that imposing 12 h of intermittent lighting during scotoperiod reduces the incidence of ascite mortality.

Increasing susceptibility of broiler chickens to ascites syndrome has coincided with a continuing genetic and nutritional improvement in their feed efficiency and growth rate. Imbalance between oxygen supply and the oxygen required to sustain rapid growth rates and high food efficiencies is believed to be the primary cause of ascites. This imbalance is caused by exogenous and/or endogenous factors.Selection in fast growth broilers, have also resulted in the development of birds with changed anatomical, physiological, metabolic and hematological parameters including thyroid hormone activity, partial pressure of O 2 and carbon dioxide in venous blood, cardiac β-adrenergic receptors and hematocrit levels that coincide with susceptibility to ascites in broiler chickens. Observations to date have indicated that the structural or endocrine changes are often linked with ascites susceptibility and may be influenced during the early stages of development, embryogenesis and incubation. In this review, particular attention is paid to the interactions between endogenous and exogenous factors as predisposing factors for development of ascites syndrome. Additionally, preventive management procedures like different lighting schedules, feed restriction protocols and supplementation of feed with antioxidants which reduce the incidence of ascites in broiler chickens are highlighted.

The present study was carried out to determine, first, the cardiac b -adrenergic receptor characteristics of broiler chick embryos exposed to two different CO2 levels during the last stage of embryonic development, and second, the prophylactic effect of b 1 -adrenoceptor blocker on right ventricular hypertrophy in broiler chickens. High CO 2 embryos showed significantly higher haematocrit values, higher partial pressure of CO 2 levels and lower partial pressure of O 2 levels than those of normal CO 2 embryos. Exposure of chick embryos to high CO 2 levels reduced the binding capacity of myocardial b -adrenergic receptors compared with those embryos incubated at the normal CO 2 level. Atenololsupplemented diet numerically reduced ascites incidence in broiler chickens (7%) compared with birds fed the control diet (15%). In conclusion, these data support the important role of the b -adrenergic receptor in the cardiovascular system for cardiac output, and secondary to pulmonary hypertension syndrome.