The relationship between heat stress, survivability and blood composition of the domestic chicken

In order to better understand the metabolic changes leading to death which take place in the chicken during acute heat stress, the blood composition was determined in surviving and non-surviving chickens. The following blood analytes were determined: glucose, uric acid, serum total proteins, inorganic phosphate, total and ionized calcium, sodium, potassium, triiodothyronine, thyroxine. The haematocrit, erythrocyte creatine kinase (total and the isoenzymes) and haemoglobin fractions were also measured. Blood was taken from the wing vein before and after heat stress. Eight-week-old "Anak 2000" broilers were kept in a climate 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 heat-stressed surviving and non-surviving chickens were seen in the blood levels of glucose, uric acid, total and ionized calcium, potassium, triiodothyronine, erythrocyte creatine kinase (total and isoenzymes). Differences 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.