الفهرس 
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Abstract
1. INTRODUCTION
In the last twenty years, the poultry industry in Egypt,
particularly chickens, depends mainly on some exotic breeds while our
local breeds and/or strains are somewhat negligible. Some Egyptian
studies (Iraqi, 2008; Iraqi et al., 2012) reported that most of the native
breeds had high non-additive genetic variance and, therefore the
possibility of improvement of these breeds through crossbreeding could
be evidenced.
Poultry industry has a history of using crossing to establish
broad genetic basis for the development of new breeds or lines and to
find superior crossbreds. The main purpose of crossing is to produce
superior crosses to improve performance of local chickens and to
combine different breed characteristics in crosses having valuable
performance for growth and egg production (Saadey et al., 2008;
Lalev et al., 2014). The Egyptian strains of chicken had high additive
and non-additive genetic variations as reported by many investigators
(Iraqi, 2002; Iraqi, 2008; Iraqi et al., 2012; Iraqi et al., 2013). The
results of most crossbreeding experiments showed that crossing
between the local breeds of chickens with other local ones was
generally associated with the existence of considerable heterotic effects
on egg production traits (Iraqi et al., 2007, 2012; Hanafi and Iraqi,
2001; Saadey et al., 2008; El-Tahawy, 2020; Soliman et al., 2020).
Partial recording of egg production in pullets is used to increase
the efficiency of genetic selection as well as to shorten the generation
interval. Results of many investigators showed that more genetic gain
could be obtained in egg production when using partial recording (El-
Labban et al., 2011; El-Attrouny, 2011 and Venturini et al. 2012).
- 2 - Introduction
Improving chicken productivity in terms of growth and egg
production is a major goal of the poultry breeding, and crossbreeding is
one of these tools for exploiting genetic variation. However, the
information for crossbreeding effect on some egg production traits, e.g.
egg partial recording, clutch size, pause periods, .. etc in chickens are
scarce. In Egypt, few modern reports on these traits were documented
(El-Labban et al., 2011, Iraqi et al., 2012 and El-Attrouny et al.
2019). Therefore, the objectives of the present study were: (1) To
estimate heritability and predicted breeding values (PBV) for growth
and egg production traits using single trait animal model, (2) To
estimate crossbreeding components (direct additive effects, maternal
genetic effects, direct and maternal heterosis) for the studied traits, (3)
To compute the superiority of three-way