Cardiac index, oxygen delivery, and tissue oxygen extraction in slow and fast growing chickens, and in chickens with heart failure and ascites: a comparative study

The present study examines the differences in blood gas parameters, cardiac output, cardiac index, oxygen delivery and tissue oxygen extraction in slow growing chickens (leghorn and feed restricted broilers), fast growing chickens (broilers fed ad libitum) and chickens with fulminant heart failure and ascites. In comparison to leghorns, broiler chickens had lower pO(2) and O(2) saturation levels in venous blood (P < 0.001). At the age of 35 days, broilers had arterial and venous pO(2) significantly lower than 7-day-old broilers (P < 0.05). Overall, blood pO(2) and O(2) saturation tended to decline, and CO(2) content tended to increase with age. Chickens developing ascites had lower blood pO(2) and O(2) saturation levels, and higher blood CO(2) content in comparison to normal chickens (P < 0.05). In comparison to other chickens, ascitic chickens had the lowest pO(2) and O(2) saturation, and highest CO(2) content in both venous and arterial blood (all P < 0.001). Broilers at 35 days of age had higher arterial O(2) content than leghorn chicks, and there were only minor differences between normal and ascitic chickens. However, ascitic chickens had the lowest venous O(2) content (P < 0.001), but the highest tissue O(2) extraction index (P < 0.001). Cardiac index was higher in leghorn chicks than in broilers (P < 0.001). Ascitic birds had the lowest cardiac index (P < 0.001). Oxygen delivery was higher in leghorns than in broilers (P < 0.001). Ascitic birds had the lowest oxygen delivery index. The present study has identified significant differences in previously unexamined performance indicators of the cardiovascular system between slow growing chickens, fast growing chickens and chickens with heart failure. Low cardiac index in broiler chickens appears to be the key haemodynamic problem leading to hypoxaemia and ultimately cardiovascular failure in fast growing broilers.