BLACK, J; DZIALOWSKI, E; KHORRAMI, S; BURGGREN, W; Univ of North Texas, Denton: Metabolism and Hematology of Developing Chicken Embryos After Acute and Chronic Hypothermic Exposure
Chicken hatchlings actively defend body temperature shortly after hatching. The maturation of these thermoregulatory mechanisms must begin during late incubation. To determine the influence of incubation temperature on the onset of metabolic and cardiovascular compensation to cooling, eggs were incubated at either 38° C or 35° C (hypothermia). We measured metabolism (VO2), dry body mass, hemoglobin (Hb), hematocrit (Hct), and P50 in stage 41-42 and 43-44 embryos from both temperatures. The ability to metabolically compensate during gradual cooling was measured acutely as egg temperature declined from 38° C to 30° C. Stage 41-42 embryos incubated at 38° C significantly increased VO2 (p=0.012) as egg temperature decreased from 38° C (0.38 ml O2/min) to 34° C (0.43 ml O2/min). This was followed by a decline to 0.34 ml O2/min at an egg temperature of 30° C. In embryos incubated at 38° C, Hb and Hct were significantly higher (both p<0.05) at stage 43-44 than at stage 41-42, but this pattern was not observed in the 35° C incubated eggs. The oxygen affinity of the 38° C incubated embryos (P50 = 46.8 torr) was significantly higher than that of the 35° C incubated embryos (P50 = 30.6 torr). The P50 decreased from stages 41-42 to 43-44 in both groups. Body mass increased with an increase in stage of development in both 38° C and 35° C incubated eggs (p<0.001 and P=0.001). There were no differences in body mass between the two incubation groups at a given stage. Chronic incubation in hypothermia alters the development of all the hematological properties examined, and could lead to a decreased ability to respond to periods of hypothermia upon hatching.
