THE DEVELOPMENT OF THERMOREGULATION IN TURKEY AND GUINEA-FOWL HATCHLINGS - SIMILARITIES AND DIFFERENCES

The development of thermoregulation was studied in turkeys (Meleagris, gallopavo, 60.5 g) and guinea fowl (Numida meleagris, 33.5 g) from 2 to 24 h after hatching. Thermoregulation was measured at different age s during 1 h of cold exposure (20 degrees C). Final body temperature r ose linearly with age in turkeys, but reached a plateau in guinea fowl between 12 and 16 h. At 2h after hatch final body temperature was hig hest in guinea fowl, while at 24 h after hatch there was no difference between the species. The development of mass-specific metabolic rate with age resembled the pattern of final body temperature. At 2h post-h atch mass-specific metabolic rate was highest in guinea fowl; however, at 24 h post-hatch there was no difference between the species, since mass-specific metabolic rate reached a plateau in guinea fowl at 16 h . In turkeys mass-specific dry thermal conductance decreased with age initially, while in guinea fowl it remained stable. Nevertheless, at b oth 2 and 24 h after hatch mass-specific wet conductance did not diffe r significantly between the species. In turkeys mass-specific wet cond uctance increased initially. This increase in mass-specific wet conduc tance may be due to the rapid onset of feather growth in turkeys. The O-2 consumption per breath doubled during the first 24 h in turkeys bu t remained stable in guinea fowl. This suggests that at least two diff erent developmental patterns of O-2 intake exist within Galliformes. T he results show that 2 h post-hatch the thermoregulatory ability was l owest in turkeys, despite their larger body mass. However, at 24 h pos t-hatch the difference between the species was not significant, becaus e the thermoregulatory ability had increased more in turkeys.