The objective of this study was to find a relationship between blood gas parameters and thyroid hormone
activity with ascites syndrome in broiler chickens exposed to cold temperature and receiving a high quality
diet. One hundred and sixty one-day-old broiler chicks were randomly divided in two equal groups. To
increase the incidence of ascites, chicks of group 1 were fed ad libitum with a higher condensed diet and
reared under a lower ambient temperature. Weekly, blood gas parameters and thyroid hormone levels were
measured and growth performance was recorded. The hearts of dead and slaughtered birds were examined for determination of arterial pressure index (API) values. Ascites incidence was clearly higher in cold-exposing chickens compared with normal rearing chickens. The mean values of carbon dioxide tension of group 1 chickens were significantly higher compared with group 2 chickens at the 4th and 5th weeks of age, while the phenomenon of oxygen was reversed in these two experimental groups. The function of thyroid hormone levels were changed at week 4 of age, as observed for blood gas parameters. In conclusion, the present study showed a significant association between thyroid hormones functions, the levels of venous blood carbon dioxide and oxygen pressures in the two groups of chickens.