Evaluation of vectorelectrocardiographic analysis of young broiler chickens as a predictive index for susceptibility to ascites syndrome.

Vectorelectrocardiographic (VCG) analysis was performed on 50 male broiler chicks (1 week of age) before placement in a hypobaric chamber. During 5 weeks of exposure to hypobaric hypoxia (simulated altitude of 2900 m), all recorded mortality (38%) was due to the development of ascites syndrome. There was a positive correlation (r = 0.74, P less than 0.01) between the increment in the frontal plane mean resultant vector magnitude divided by body weight (designated as the cardiac index [CI]), with the severity of right ventricular enlargement. Chicks developing ascites syndrome had a greater CI (P less than 0.05) at 1 week of age when compared with chicks that did not develop the syndrome. Therefore, the CI calculated by VCG analysis recognizes right ventricular enlargement, suggesting that a pre-hatch or early post-hatch functional cardiac stress has occurred, predisposing the 1-week-old broiler chick to ascites syndrome. Application of the CI has a physiological index may prove useful in future studies targeted for selection of ascites syndrome resistance in broiler chickens.