A four-years crossbreeding experiment was performed involving two synthetic rabbit lines of APRI (A) and Moshtohor
(M) where bucks of the APRI line were mated with does of the Moshtohor line to produce F1
crossbred (½A½M),
followed by inter-se mating to obtain F2
crossbred (½A½M)2. A total of 669 litters produced from 184 bucks and 394
does were used in analyzing litter size at birth (LSB) and weaning (LSW), litter weight at birth (LWB) and weaning
(LWW) and pre-weaning mortality (PM). Heritability estimates for the targeted traits were low to moderate, ranging
from 0.11 to 0.27. APRI line had the lowest range in predicted breeding values (PBVs) for all litter traits. The ranges
in PBV for the four genetic groups were high and ranging from 0.59 to 1.0 kit for LSB, 2.4 to 3.0 kit for LSW, 26.5 to
33.9 g for LWB, 411.6 to 515.5 g for LWW and 20.9 to 24.8% for PM. The estimates of direct additive effects (
GI) and
maternal effects (
GM) for litter traits were in favour of the Moshtohor line with percentages ranging from 1.2 to 16.3%
for GI
and 1.4 to 20.5% for GM.
The estimates of direct heterosis (
HI) and maternal heterosis (
HM) were significantly
positive for most litter traits with percentages ranging from 2.4 to 55.8% for HI
and 1.8 to 34.6% for HM.
In practice, it
is recommended to use the APRI line as a sire group and Moshtohor line as a dam group in the crossbreeding program
to synthesize new synthetic rabbit lines in Egypt.