الفهرس 
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Abstract
A simple crossbreeding experiment between Gabali (G) bucks with Hyplus (H) does was performed to evaluate crossbreeding effects (direct additive genetic effects, maternal effects and direct heterosis) for litter traits (LSB, LSW and LWB), milk yield traits(weekly milk yield 14(WMY14) and weekly milk yield 21(WMY21) and growth traits (body weight at (BW5), (BW7), (BW9), (BW11) and (BW13) weeks of age as well as daily weight gains during the age intervals from 5 to 7 weeks (DG5-7), 7 to 9 weeks (DG7-9), 9 to 11 weeks (DG9-11), 11 to 13 weeks (DG11-13) and 5 to 13 weeks (DG5-13). This work was consisted of three groups, the first was pure HyPlus (♀H x ♂H), the second was pure Gabali (♀G x ♂G) and the third was hybrid (♀H x ♂G). Estimates of heritability were mostly low to moderate for litter, milk and growth traits. The percentages of crossbreeding effects (direct additive and maternal) on LSB and LWB were significantly (P≤0.01) in favour of Gabali breed. The percentages of direct heterosis were not significantly for litter traits. The percentages of crossbreeding effects (direct additive and maternal) on WMY14 and WMY21 were significantly (P≤0.01) in favour of Gabali breed. The percentages of direct heterosis were significantly for milk traits. The percentages of direct additive effects on body weights were significantly (P≤0.01) in favour of Gabali breed by 22.1, 31.2, 32.8, 31.1 and 25.2% at 5, 7, 9, 11 and 13 weeks and by 35.4, 38.1, 21.9, 3.7 and 27% for DG5-7, DG7-9, DG9-11, DG11-13 and DG5-13, respectively. The percentages of maternal effects on growth traits were also significant in favour of Gabali breed and ranged from 22 to 34.8% for body weights, and ranged from 4.7 to 43.4% for daily weight gains. The percentages of direct heterosis were significantly positive by 11, 19.1, 20.3, 19.7 and 16.5% for body weights at 5, 7, 9, 11 and 13 weeks and by 25.6, 27.2, 17.3, 3.5 and 17.9% for DG5-7, DG7-9, DG9-11, DG11-13 and DG5-13, respectively. Purebred Hyplus (H♂×H♀) showed improvement in the litter traits compared with the other genetic groups. Crossing Gabali with Hyplus rabbits resulted in desired heterotic effects, which could be useful for producing crossbred meat rabbits with high body weights at marketing. According to the estimates of direct additive genetic and maternal effects, Gabali breed might be used as a sire-group with Hyplus line as a dam-group in synthesizing new rabbit lines characterized with good growth performance and to improve litter traits in Egypt.