THE RELATIONSHIP BETWEEN HEAT-STRESS, SURVIVABILITY AND BLOOD COMPOSITION OF THE DOMESTIC CHICKEN

In order to better understand the metabolic changes leading to death w hich take place in the chicken during acute heat stress, the blood com position was determined in surviving and non-surviving chickens. The f ollowing blood analytes were determined: glucose, uric acid, serum tot al proteins, inorganic phosphate, total and ionized calcium, sodium, p otassium, triiodothyronine, thyroxine. The haematocrit, erythrocyte cr eatine kinase (total and the isoenzymes) and haemoglobin fractions wer e also measured. Blood was taken from the wing vein before and after h eat stress. Eight-week-old ''Anak 2000'' broilers were kept in a clima te chamber at 24 degrees C/40% relative humidity during a 14-hour day, and at 20 degrees C/40% relative humidity during a 10-hour night. The birds were subjected to heat stress by exposing them to 40 degrees C/ 30% relative humidity for 3 hours. Significant differences between hea t-stressed surviving and non-surviving chickens were seen in the blood levels of glucose, uric acid, total and ionized calcium, potassium, t riiodothyronine, erythrocyte creatine kinase (total and isoenzymes). D ifferences were also seen in the levels and ratio of the 2 haemoglobin fractions. The significance of these changes, and their potential use as markers for heat resistance is discussed.