الفهرس 
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Abstract
6. SUlI1IDY
A crossbreeding experiment was carried out in Gezireit EI-Sbeir Experimental
station (about 12 kJlto tbe north of cairo), Animal Production Research
Institute, Binistry of Agriculture, Egypt during two consecutive years started
in September 1988. One local breed (Baladi Red, BR and an exotic one Hew Zealand
White, HZ) were used in sucb experiment to estimate direct heterosis,
maternal additive effects and direct sire effects on some economic traits in
rabbits (e.g. litter traits, reproductive interval traits, postweaning body
weigbts and gains and carcass performance).
Performance records of litter traits including litter size and weigbt and
Ilean bunny weigbt (at birth, 21 days and at weaning), number born alive and
preweaning litter gain and .ortality, while reproductive interval traits
included insemination period, days open, gestation length and kindling interval
were taken on 603 litters. Data of body weigbts (at 5,6,8,10,12 weeks) and
daily gains <at intervals of 5-6, 6-8, 8-10, and 10-12 weeks) on 2153 weaned
rabbits were collected. carc,-, performance (weights and percentages of bot
carcass, giblets, salable carcass, bead, fur, blood viscera) on 213 _Ie rabbits
were recorded at 12 weeka of age.
I selected set of orthogonal Unear contrasts were c.-puted to quantify
differences attributable to sire breed, daa breed and direct heterotic
effects. Resut ts obtained could be su..aried as:
(1) ,Utter tra1u. Estiaates of coefficient of variation (CV) for, litter
and. interval traits vere high and ranged froe 22.0 to SO.”. Litter traits
aeasurecl at weaning vere high in their phenotypic variation than those litter
traits .easured at birth. Litter traits .easurecl at weaning significantly
affected by year of kindling, vhile litter trait ••••• ured at birth and interval
traits were not algn1fieantlf affected. Vlnter-kiDdlings recorded the
large.t litter .ize and ”,v1e.t litter weight and gain of litter up to weaning
along with the loveat prevean1ng ~rtaUtf cc.pand to aut.u- and sprlngkindlings.
Spring-bon litters recorded the abortest interval traits relative
to autuan- or winter-bon litters. britl bU. lDCOUSlstent effect aod contributed
llttle to the varlat.ton of.n Utter and illterval traits. vith the
exception of preweaning aortautr. Buck-breed effect contributes little to the
-Iovvariation
of litt.r and int.rval trait •• vhU. doe-broecl.ffect •••••of consid-
.rabl. ieportanc. in aost ••.•••. Int.rval traits and litt.r traits at 21 day.
of ag. v.r. not significantly aff.cted by buck-br.edx doe-breed interaction.
vhile litter trait. at veaningvere significantlY affect.d by suchinteraction.
lIZbroeclbad superior litt.r perforaancecomparedto DRbreed. vbile
int.rval trait. of DRrabbit. vera shorter than HZbr.ed. Estimat.s of dir.ct
bet.rosi. vere significant for mo.t litt.r and interval traits studied.
cros.bred litt.rs obtainedfromnotingDRbUCksvith HZdoe. v.r. as.ociat.d
vith sup.rio
r
heterotic .ff.ct. coaparedto those litters obtained from tbe
rover.e noting, i .•. litt.rs dolIledby HZbreed are superior in their .eternity
ccaparedvitb DRnot.rnity. In tem’ of reproductive int.rvals, DR-daMd
r.corded shorter int.rval. compar.dto HZ-domelidtters. Bat.malbreed
eff.ct
onall litt.r traits vere in favourof HZ br.ed. although tho diff.re
nc
••
botv.en the tvo br.ed. vere not significant. Tbelinear contrast. of direct
sire effect for all litter and interval traits vera ·n.arly similar and not
significant. Hov.ver. maternal-br.ed .ffect. appearedto be eore ieportant
than pat.mal-broecl.ff.cts in influ.ncing ””.t litt.r and int.rva
l
trait •.
Hz-sired litters bad bigb.r dir.ct sir •• ff.cts comporodto DR-siredlitter ••
vbUe DR-siredlitt.rs r.corded sborter reproductiveint.rval relative to IIZsired
11tters.
(11) arowtb traits f1!!l<!Y OIfI1gfJt andda1Jr pi”’)’ Estimat.s of ev for eo.t
qrovth traits vere high andrangedf•.•• 10.3 to 40.2_. Effects of year and
s••• on of birth contribut. significantly in the variation of IlOstbodyvoigbt
s
andgains, vhU. parity and sex bada little contribution. Autgn-bororabbits
vera g.nerally higher in their qrovththan tho.. rabbits born duringvint.r
and spring. HZ-siredrabbits vor. _vi.r in voighta and galns c_
ed
to
BR-sir.d rabbits. vhile HZ-andBR-daaedrabbits vera nearly .ieilar in their
postveanlngvoights and gains. Significant diff.rences in favour of IIZ-sir.d
rabbits vore evidenceddaring later .,.S of qrovtb <at 10and 12_ks). vhUo
both broodsvore not .ign1ficantly diff.red in their bnod _temlty. Sirebroecl
x daa-broecil_etion affected <p<O.OoIr p<o.ooll ••• t bodl’voights
and gains studied• ...., •• igbta andtIa11ygal’” of the tva panbrads uere not
significantlY diff.rent. H.terosis .ont•.••t for ..-t gr<Nth.c:r” o1g- .... ,.~-
nlficant: betorDlis percentag.s rongedf•.•• 5.0’ to 10.0’ for bodf·.lghta and
-161-
frOil 1.4’ to 18.9% for daily gains. Batemal-breed effects on BOst postweaning
weights and gains were insignificant, while sire-breed contrasts for some
weights and gains proved significant effects, postweaning growth of BR-damed
rabbits were generally higher in ~heir .aternity compared to HZ maternitYj
while HZ-sired rabbits were superior in their paternity at later ages (at 10
and 12 weeks of age). However, maternal-breed effects appeared to be less
important than paternal-breed effects in influencing .ost weights and gains
studied.
(iiI) carcass traits. Estimates of CV for weighed carcass traits are
.aderate or high and ranged from 10 to 30%. The patterns of change of yearj
season or parity effects on carcass traits were inconsistent and not significant.
Autumn and winter born rabbits recorded the highest edible earcase.
while spring-born rabbits recorded the lowest performance. Sire-breed was of
considerable importance in the variation of some carcass traits, while dambreed
and sire-breed x dam-breed interactions contributed little. carcass of
BR-damed rabbits are higher than those rabbits mothered by HZ breed, although
both breeds are not significantly different in their breed Ilaternity. HZ x HZ
aating resulted in rabbits with heavier carcass and with lighter non-edible
carcass (blood and viscera) compared to the BR x BR aating. Insignificant positive
direct heterosis was observed for aost carcass traits. Crossbred rabbits
obtained from aating sires of lIZwith dus of BR were associated with SOll8
heterotic effects coapared to tbose crossbred rabbits obtained frca the
reverse -.ting. Batemal-breed effects appeared to be less t..portant than patemal-
breed effects in influencing IIOstcarcus traits. carcass traits of Ddued
rabbits vere higher In their aaterni ty coapared vith RZ aatemi ty,
although the differences ••.• not significant. This -- that breed -.ternity
for carcass traits vas in favour of BR daD. High edible carcass vas observed
for BR-sired rabbits, vhU. non-edible carcass wastes (blood and viscera) vere
recorded for RZ-sired rabbits.