This experiment was conducted to investigate the effects of pre-incubation
storage period of hatching egg, incubation relative humidity, and parental chickens,
strain and age on hatchability performance. Two preincubation storage periods (3 or
14 days) and three incubation relative humidity (RH) levels (55, 60 or 65%) were
investigated. A total number of 1155 hatching eggs produced by 40- or 60-wk-old
Mamourah (M) and Gimmizah (G) hens were used in this study. Prior to incubation
hatching eggs were stored for 3 or 14 days (at a range of temperatures between 14-
17°C and 62-65% RH).Eggs were incubated at a temperature of 37.8 °C with RH of
55, 60 or 65% for the first 18 days, then 65% RH for the last three days. Results showed that, post-stored egg albumen height was negatively
affected for eggs from older hens (60-wk-old). Post storage egg albumen height was
decreased while albumen pH was increased as the preincubation storage period
extended to 14 days. Egg weight loss during the first 18 days of incubation was
significantly higher for eggs of M (13.2%) than for those of G (12.9%), and, greater in
eggs from 60-wk-old hens (13.2%) than in those from 40-wk-old hens (12.7%). The
greatest egg weight loss (13.8%) was observed at incubation RH of 55%, and the
lowest one (12.3%) was recorded under 65% RH. Eggs fertility and hatchability were
not affected by strain of chickens, but they were significantly affected by parental age,
length of presetting storage period, and incubation RH. Fertility and hatchability
percentages were higher for eggs laid by 40-wk-old hens than for those of 60-wk-old
hens, being 91 4 and 90.2%, and 87.8 and 83.45% for fertility and hatchability,
respectively. The best egg fertility and hatchability percentages were obtained under
incubation RH of 60%, and the worst ones were recorded at 65% RH. There were
significant differences in incubation time of eggs due to the effects of chickens strain
(491.9 VS. 492.8 h in G and M, respectively) and age ( 491.8 VS. 492.9 h in eggs
produced by 40- and 60-wk-old hens, respectively), length of presetting storage period
(489.7 VS. 495.1 h for eggs stored for 3 and 14 days, respectively), and incubation RH
(490.4, 492.7 and 493.6 h at 55, 60 and 65% RH, respectively). Embryonic mortality
was significantly increased in hatching eggs from older hens (60-wk-old), in eggs
stored for 14 days prior to setting, and in those incubated at 65% RH. Average hatch-
weight of chicks was not affected significantly by strain and age of parental chickens
or the length of preincubation storage period of hatching eggs, while it was inversely
related to the level of incubation RH.