This study aimed to determine the effects of injecting incubated eggs:
produced by 40-or 5O-week-old of Mamourah and Gimmizah breeder hens. with
either Growth hormone (0.02 or 0.04 tU) per eg~ or a thyroid-hormone (Eltroxin) (0.10
or 0.15 ~g1egg). during the 9,h. 151/1 or 17 day of the incubation period. on
hatchability characteristics and growth performance of hatched chicks. Data of the
treated eggs were compared with those of a control group (eggs injected with distilled
water). Hatchability percentages and chicks hatch-weight were higher (P$O.01)
whereas embryonic mortality rate was lower (P~O.01) in eggs produced by Mamourah
than in those of Gimmizah breeder hens. Eggs produced by the 40-week-old hens
showed higher (PsO.01) hatchability and lower embryonic mortality and chicks hatch-
weight than those produced by the so-week-oid hens. Hormonal in 0'10 injection on
the 9^1h day resulted in the highest (P~O.OS) hatchability and chicks hatch-weight and
the towest (PSO.OS) embryonic mortatity. followed by those obtained with in ovo
injection on the is" and the1t^h day of incubation. Eggs injected with growth hormone
(GH) gave significantly higher {PsO.OS} hatchability and chicks hatch-weiqht, and
lower embryonic mortality than did lhose injected with Eltroxin. While the worst
hatchability. chicks hatch-weight and embryonic mortality were attained with the
control eggs. Regarding the post-hatch performance of chicks. body weights of
Mamourah chicks were higher than those of Gimmizah chicks either at 4. 8 or 12
weeks of age. The post-hatch body weight of chicks hatched from eggs produced by
the 60-week-old hens was heaver at 4 weeks of age and lower at 8 and 12 weeks of
age. than that of chicks hatched from eggs produced by the 40-week-old hens. The in
0'10 hormonal injection on the 9^th day of incubation resulted in superior body weight
(PSO.OS) of chicks at \ 8 and 12 weeks of age. Followed by those obtained with in
ova injection on the 15' day and then Those of the 17^th day of Ihe Incubation period.
The highest hatch weight of chicks was achieved by eggs injected with 0.02 IU (GH)
while the lowest weight was recorded for the control group. and these significant
differences were observed in the post-hatch weight of chicks. and persisted 10 12
weeks of age. The post-hatch feed intake and feed conversion of chicks were not
affected by the age and strain of the breeder hens or time and dose of the in ova
hormonal injection. Viability of the post-hatch chicks was not significantly affected by
strain or age of breeder hens. In ova hormonal injection on the 9^th and 15^th days of
incubation produced chicks of significantly higher (post-hatch viability than that of
chicks hatched from eggs injected on the 17 day of incubation. The post-hatch
viability of chicks hatched from eggs injected with 0.02 IU GH did not differ
significantly from that of the control. However. The other hormonal treatments gave Chicks of lower post-hatch viability. Being the lowest with in ovo injection with 0.15 J.l9 Eltroxin.