الفهرس 
I N TRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The present experiment has been carried out at the Poultry
Experimental Farm of the Faculty of Agriculture, Minufiya University,
Shebin El-Kom, Egypt, during the period from 2013 to 2017 on Norfa
chickens. Total of 475 dams were used in the present experiment in the
base population, first and second generations. Independent culling levels
(ICL) method of selection has been applied on the selected flock
(x+.5sd).The criterion of (ICL) method of selection was to select hens
having at least average EN90 d + 0.5 sd on condition that egg size and
body weight should be around the average flock.
Results obtained and conclusions can be summarized as follows:
-The actual genetic gains for EN90d and EN42WK were high from the
expected genetic changes throw the base population, first and second
generations by applied the Independent culling levels.
-The selected line was excellent this of control line for productive traits in
Norfa laying hens.
-Concerning to phenotypic and genetic parameters, the heritabilites estimates showed
that ASM had low h2 estimates, both of BWSM and BWM showed moderate h2
estimates, EWSM showed moderate to high h2 estimates while EWM had moderate h2
estimates and the heritability estimates for EN90d and EN42wk were moderate to high.
- Generally, Norfa layers proved to have the advantage of early sexual
maturity.
- Norfa layers, in general have moderate egg size and this is mainly due to
light body weight. More experiments are needed to increase egg size.