The research was implemented in 2018 at the Institute of Zoology of ANAS. The experimental part of  study was carried out in Institute's vivarium, but the analysis of results was performed in Protozoology laboratory and at the Department for Biology and its teaching methods of Azerbaijan State University. The studies were conducted on pheasants (Phasıanus colchicus colchıcus) incubated in the vivarium of the Institute. The birds were weighed individually, separately, one by one on an electronic scale (Adventurer Pro) with an accuracy of 0.1 mg, in the first two months of postembryogenesis (1, 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 34, 38, 42, 50 and 60 days) before feeding in the morning.
It was determined that recorded jumps of the pheasants of all ages manifests itself in the form of peaks in the dynamics of relative weight gain and relative growth rate during the development and growth of both male and female individuals. The highest peak in the dynamics for relative weight gain (RWG) and relative growth rate (RGR) of pheasant chicks is observed in 10-day birds (64.24% and 94.65%, respectively), although there is decrement in both indicators of male and female pheasants, it was noted that these indicators rise in some days. In the index of RWG and RGR of 12-60 day pheasants, the first high increase is observed in 16-day birds (♂ 32.26% and 38.46%; ♀ 31.14% and 36.89%), the second highest increase in 22-day birds (♂ 35.07% and 42.52%; ♀ 36.21% and 44.12%), the third highest increase in 42-day birds (♂ 63.10% and 62.19%; ♀ 51.17% and 68.76%). The decrements in the index of both RWG and RGRs is compensated in the days when the next peaks observed. The differences among all weight indicators of male and female pheasants, as well as  RWG and RGR are significant and the index of male pheasants is higher than female pheasants.