A total number of 432pullets (aged 22 weeks) from Gimmizah, Mamourah,
and Bandara strains (144 from each strain) were subjected to study. Birds were
individually caged (after sexual maturity) to classifying them into three groups
according to the time required for egg formation. Pullets of each group (48 pullets)
were distributed in 3 breeding pens (each of 16 females and 2 males). The'
experiment aimed to study the effect of strain and time spent for egg formation on
productive performance, thyroid activity and calcium absorption rate of laying hens of
different local strains. Results obtained can be summarized as follows. Bandara pullets had higher average of feed consumption (121.47 gm/hen/day). However, Gimmizah pullets showed higher feed efficiency (0.27 gm egg/gm feed).
Pullets needed less than 25 hours for their egg to be formed consumed Significantly
(p < 0.05) more feed (119.96 gm/bird/day). Feed efficiency mounted 0.26 gm egg/gm
feed in all studied groups of birds of different time needed for egg formation. Mamourah pullets had higher averages of egg production and egg mass
(62.97%/hen Iday and 31.11 gm/hen/day, respectively). However, the highest egg
weight was found in Gimmizah (49.02 gm). Pullets needed less than 25 hours for their
completely formation had higher egg production and egg mass. Significant effect
(p < 0.05) on the rate of egg production only was found due to time of egg formation.
Eggs from Gimmizah pullets had significantly the highest mean of shell thickness
(0.354 mm) than those of Mamourah (0.344mm) and Bandara (0.339mm). Eggs laid by Bandara pullets had significantly higher fertility percentage
(90.43%). On the other hand, eggs laid by Mamourah pullets had significantly higher
hatchability percent (90.68%). Time required for eggs to complete their passage along
the oviduct had highly significant effect (p < 0.001) on hatchability percentage .The total
absorption of calcium and absorption per gm dry matter were found to be mostly
higher in Gimmizah followed by Bandara then by Mamourah pullets. Pullets needed
less than 25 hours to complete its egg formation had significantly higher in total
calcium absorption and absorption per gm dry matter. The greatest values of total
calcium absorption and absorption per cm length of the small intestinal was attained in
ileum followed by jejunum and duodenum, respectively. Highly significant variations
(p < 0.001) in total calcium absorption, absorption per gm dry matter and per cm length
were found due to different intestinal regions. Mamourah pullets had significantly
(p < 0.001) the highest level of plasma T3 and T3/T 4 ratio. On the other hand, pullets of
Gimmizah had the highest level of plasma T4. Pullets needed less than 25 hours for
egg formation had higher plasma T3 level and T3/T4 ratio, while pullets needed more
than 26 hours for egg formation were high in plasma T4 level.