EMBRYONIC HEART-RATE DURING DEVELOPMENT OF DOMESTICATED BIRDS

We have measured noninvasively the embryonic heart rate (HR) of the Japanese quail (Coturnix coturnix japonica), the chicken (Gallus domesticus), the duck (Anas platyrhynchos), the turkey (Meleagris gallopavo), the peafowl (Pavo cristatus), and the Chinese goose (Anser cygnoides) during approximately the last half of the incubation period. The average daily HR was determined over 30 s, every 5 min for 30 min. The HR was variable, particularly toward the end of incubation and during pipping. The time trend of changes in daily HR was similar in quail, chicken, and turkey eggs: a temporal increase occurred at 60%-70% of the incubation period, with a subsequent decrease toward the end of prepipping development, and then an increase with the breathing of air by the lungs. The duck and goose embryos decreased the HR during the last stages of prepipping development. Although the changes in internal pipping HR of the duck were various, the HR of the goose was predominantly increasing during pipping. A gradual increase in HR toward the end of incubation occurred only in the peafowl embryo. The prepipping HR of these embryos had a significant allometric relationship with fresh egg weight.