الفهرس 
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Abstract
A crossbreeding experiment was carried out during three consecutive
production years started in September, 1993 in fvfaryout Experimental Station
belonging to the Desert Research Center, Ministry of Agriculture and Land
Reclamation, Egypt. This station is located in a newly reclaimed area 35 km
to the south east of Alexandria. The experiment was conducted using Gabali
(Egyptian local) and Californian (exotic) breeds with the aim of investigating
and quantifying the effects of some non-genetic factors, mating or breed
group, crossbreeding and heterosis in addition to maternal additive and direct
additive effects on litter, doe reproductive, progeny and carcass traits.
Results could be summarized as follows:
5.1. Litter traits
Actual means of litter traits (LSB, LS21, LSW, LWB, LW21 , L’/WII,
MBWB, MBW21 , MBWW and PM) are within the ranges of the available
literature. The CV% of these traits ranged from 10.4 to 60.1 %.
Year of kindling, month of kindling and parity did not exert any
significant effect on most litter traits. Parity did not show any consistent
pattern of effect on these traits.
Most litter traits varied non-significantly with mating group.
Differences between Cal and Gab rabbits were not significant for most of
these traits and they were generally in favour of Cal rabbits. Crossbreeding
between these two breeds resulted in negative heterotic effect on most litter
traits.
/’ Maternal additive effect was mostly non-significant but their contrasts
were in favour of litters born by Cal does. AJso, direct additive effect was
mostly non-significant and in favour of litters sired by Cal breed.
5.2. Doe reproductive traits
Actual mean of NSC is relatively higher than those reported in the
available literature while those of DO, KI and GL are lower than those cited
from the previous research work. Estimates of CV% of NCS, DO and KI are
relatively high.
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Year-of-kindling effect was significant (P<O.01) on NSC and KI but not
so on Do and GL. Both months of kindling and parity did not contribute
significantly to doe reproductive traits of the study. Parity effect did not show
any definable trend on NSC and DO but caused the increase of KI and GL
with advance of parity order.
NSC, DO, KI and GL were found to be non-significantly influenced by
mating group. The differences between Cal and Gab for these traits were
also non-significant but in favour of Gab rabbits. Heterosis contrasts for NSC,
DO and KI were positive but non-significant, i.e. crossbreeding in this work
did not improve the performance of those three traits.
Maternal additive effect on doe reproductive traits was not significant
and in favour of litters produced by Cal does. Also, the direct additive effect
on these traits was not significant but in favour of litters sired by Gab bucks
for NSC, DO and KI.
5.3. Progeny traits.
Actual means of weaning and post-weaning body weights and daily
gain traits up to 16 weeks of age are within the ranges of the available
literature while those of post-weaning livability traits Lip to 16 weeks are lower
than their correspondings reported in the Egyptian research. Estimates of
CV% ranged from 4.15 to 22.27% for body weight and daily gain traits and
from 42.86 to 81.17% for livability traits.
Effect of year-of-birth was not significant on weaning and postweaning
body weight and daily gain but significant (P<O.01) on post-weaning
livability up to 12 and 16 weeks of age. Month-of-birth contributed
significantly (P<O.05, P<O.01 or P<O.001) to most body weight traits, postweaning
daily gain from eight to 12 weeks and to all post-weaning livability
traits. Parity effect was non-significant on most body weight traits, significant
(P<O.05, P<O.01 or P<O.001) on post-weaning daily gain from eight to 12
weeks and from four to 16 weeks of age and all post-weaning livability traits
studied. Most body weight traits, daily gain from eight to 12 and 16 weeks of
age and post-weaning livability up to 12 and 16 weeks of age were
significantly (Pdl05 or P<O.01) influenced by sex.
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Breed group constituted, in general, a significant (P<O.05, P<O.01 or
P<O.001) source of variation in body weight and daily gain traits but a nonsignificant
one in post-weaning livability traits. Linear contrasts showed the
superiority of Gab over Cal rabbits for body weight at most ages studied,
daily gain at all intervals of the study and post-weaning livabilities, all without
significant differences. Crossbreeding between the two breeds of the study
resulted in positive and significant (P<O.05,P<0.01 or P<O.001) heterotic
effect on most body weight and daily gain traits and positive non-significant
effect on post-weaning livability, i.e, crossbreeding has improved progeny
traits in general.
Maternal additive effect was significant (P<O.05 or P<O.001) on most
body weight and daily gain traits and non-significant on livability traits. Linear
contrasts were in favour of rabbits produced by Gab does for body weight at
most ages and daily gain at all intervals but in favour of those produced by
Cal does for post-weaning livability up to eight and 12 weeks of age. Direct
additive effect was significant (P<OO.05or P<O.001) on body weight and daily
gain at most ages and stages, but non-significant on post-weaning livability
up to eight, 12 and 16 weeks of age. . Linear contrasts were mostly in favour
of rabbits sired by Gab bucks.
5.4. Carcass traits
Actual means of carcass traits of the study reveal that performance of
rabbits for carcass traits increased with the increase of slaughter age from 12
to 16 weeks of age. CV% for different carcass traits ranged from 0.3 to
12.4% at 12 weeks and from 3.1 to 19.4% at 16 weeks of age.
Effect of year of birth was non-significant on all carcass traits at 12
weeks of age and on most carcass traits of the study at 16 weeks of age.
Season of birth did not contribute significantly to the variance of all carcass
traits at 12 weeks but significantly (p<O.05 or 0.01) to the variance of 50% of
these traits at 16 weeks of age. Parity and sex did not show any significant
effect on all carcass traits either at 12 or 16 weeks of age.
Breed group differences were significant (P<O.05, P<O.01 or P<O.OO1)
on most carcass traits at either 12 or 16 weeks of age. Linear contrast
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showed that Cal and Gab rabbits were significantly (P<O.OS, P<O.01 or
P<O.001) different for most carcass traits at 12 and 16 weeks and most of
these differences were in favour of Gab rabbits. Crossing between Cal and
Gab resulted in positive significant (P<O.05, P<O.01 or P<O.001) heterotic
effect on most of these traits.
Maternal additive effect on most carcass traits at either 12 or 16
weeks of age was non-significant but in favour of rabbits darned by Gab
does. Direct additive effect was significant on 50 and 42% of carcass traits at
12 and 16 weeks of age, respectively and in favour of rabbits sired by Gab
bucks.