Ontogenetic study of thermoregulation in birds

We reviewed our ontogenetic studies of thermoregulatory capacity in avian e mbryos in relation to metabolic responses to egg cooling. Basic understandi ng of abrupt egg cooling and quasi-equilibrium state or cooling was discuss ed together with egg's thermal conductance and heat production. Two cooling tests, which were designed to minimize the rate of heat loss during coolin g, were conducted to investigate a feeble compensatory metabolic response t o cooling in precocial and altricial embryos, and models for early developm ent of homeothermy in birds were suggested. Instantaneous heart rate (IHR) response to cooling was measured in chick embryos. The baseline of IHR rise d and became oscillating. HR oscillation may be a phenomenon related to the rmoregulation, which needs to be studied. (C) 2001 Elsevier Science Ltd. Al l rights reserved.