الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
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SUMrv’!ARY
This study was carried out to evaluate genetic parameters and to
estimate response of mass selection for 6 generations to improve body
weight in a native breed of White Baladi chickens. A total number of 20
males and 200 females was taken at random for the original population.
3ach male was mated with 10 females in individual breeding pen. Two
hatches were obtained from the same parents. The first hatch roade up the
selected population and the second hatch made up the random-bred
population. At 8 weeks of age, mass selection based on body weight ap,ljed
on the progeny of each generatIon of the selected population j~ such ~
way that tte heav1est 20 males and 200 females were selected. The pedigreed
randombred population was reproduced each generation along with the
selected populati.on. However, the 20 males used as parents were chosen
<it random, are male from each previous sire. Ea.ch male with:in each
population was mated to 10 females with only a restriction that no full
or half sib mating was avoided to prevent inbreeding depression. On hBtch,
all produced chicks were wing-banded to keep their pedigree and weiehed
at 8 and 12 weeks of age. Males of each generation of selected and
randombred populations were slaughtered at 12 weeks of aee to evaluate
dressing, edible meat, blood and feather percentages.
The collected data were adjusted for sex effect within population
and generation and were statistically analysied by the application of
nested deaign with unequal number of subclasses. Tests of significance
for the differences between means of populations a~d between generations
were done according to Duncan’s Multiple Range Test.
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Heritabilities of the studied traits as well as Genetic,
en iror-mental and phenotypic correlations among the traits were
es imated on the basia of sire, dam and sire + dam components of
V9 lances. ~he expected Genetic gain per generation of selection; also,
th expected correlated response were derived from the three components
of variances.
The obtained results can be summarized as follows:
Heritability estimates for 8 and 12 week body weights, dressing
a feather percentages were larger than those of edible meat and blood
p centages; indicating that the first four traits were highly heritable.
Heritability estimates for all traits in the selected population
w re lower than those in random population; indicating that selection
d r.eased genetic variations through fixation of genes.
Heritabilities estimated from the dam component were much hj~her
,
t” n those derived from the sire component for the majority at the
s udied traits in both populations; indicating thp presence of maternal
e fee ts.
~Jost of the genetic correlations among the studied traits based on
s re components were generally positively higher than those obtained
f am dam components in both populations; indicati.ng that sires inhere ted
eir linked and/or pleiotropic genes additively to most of the traits.
The genetic relationships between 8 week body weight and each of the
.her traits wereposi tively higher in random population than in selected
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popul tion; indicating that selec tion reduced the gene tic variabil ities
amon€ the studied traits.
igher genetic correlations were obtained between 8 and 12 week
hody eights; also, between feather percentage and each of 8 and 12
weev. body weights; indicating that improving body weight by selection
will ~e followed hy improving feather development.
~he genetic correlations between dressing ?ercentage and ea~t of
8 an 12 week bony weights were lowerly nega tive in selec ted populAtion
and ’ghly positive in random population; indicating that selection for
heaver 8 week body weight did ~ot accompany by higher dressing
perc ntage.
The genetic and the phenotypic associations between dressing
perx ntage and edible meat were positively higher in both populatj.ons;
ind sting that correlations between those two traits were automatic.
Results, also, indicated that males, females and males + females
wer heavier in selected population than in random population for 8 and
12 eek hody weights; indicating that the White Baladi breed of
chj kens responded largely to selectior. for improving body weights.
Ho~ ver, percentages of dressing, edible meat, blood and feather were
alIT s~ equal in both populations.
The average of realized progress over all generations for males +
les (48.4 grams) was nearly equal to the expected genetic gain (44.1
gr’ s). Also, ~~e correspondlng realized heritability (0.537) was nearly
eq’ 1 to thl”’ estimated heritability (0.489). Howeyer, the realized
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ger~ ’e gain was much higher tha~ the corresponding expected genetic
gA.i w i thin each generation of selection; indicating that selection r or
imp ving body wej.ght of White Baladi breed which contains consider~ble
t of additive variance is unl ikely to reach a selee t ion 1imit :in
thp- forseeab1e futures.
The results, also, indicated that males responded effectively to
sel etion than females; this was due to intensive selection pressure
sub.ected to males (5.510) than that of females (51.5%).
The results, also, showed that the change in 8 week bedy weight due
to selection was aAsoci~+ed positively with a change of about 45, 13 and
11 grams in 12 week body weight based on sire, dam and sire + darn
cO ponents of variances, re~pectively. However, the correlated response
of each percentage of dressing, edible meat, blood and feather at 12
we ks of age was rather small. This indicated that cerrelated response
of the unselected traits with moderate heritability estimates was found
w n the genetic correlation with the selected trait was large, but not.