This study was carried out within a project for five consecutive production years. This project involved Egyptian Gabali and New Zealand White (NZW) rabbits. Data of Fourteen different genetic groups of rabbits (represented by 4208 NZW and 255 Gabali purebreds and 4022 crossbreds of different genetic combinations between them with different genetic percentages in progeny produced rabbits) were used. Traits of growth (body weight at weaning (BW4), 8 (BW8) and 12 (BW12) weeks of age, as well as daily gain during intervals of 4-8 (DG4-8), 8-12 (DG8-12) and 4-12 (DG4-12) weeks of age and post-weaning livability traits during the periods from 4-8 (L4-8) and 8-12 (L8-12) weeks of age were studied. Data were analyzed using crossbreeding effect program to estimate crossbreeding genetic components (additive, heterosis and recombination effects of direct individual, maternal and paternal components, respectively).
Results showed that the differences between NZW and Gabali breeds were non-significance for all the studied traits, in spite of favorable results of Gabali breed for all traits except DG8-12.The crossbred genetic group contained 75% of Gabali and 25% of NZW blood was the heaviest in body weights at 4, 8 and 12 weeks of age. These results explained the good mothering ability of Gabali rabbit breed. Direct additive genetic effects were negative and significant for most traits. Maternal additive effects (gM) on traits of BW8, BW12 and L8-12 were significant (P<0.01) and negative estimates, beyond L8-12. Estimates of additive paternal (gP) were negative and significant (P<0.01) effect for traits of BW8 and BW12 and significantly (P<0.01) positive on livability trait of L8-12. Most estimates of direct heterosis (hI) were positive and significant (P<0.05-0.01) for all the studied traits, except DG4-12. Percentages of hI ranged from –3.9 to 32.3%, -17.33 to 5.04% and –95 to 43.75% for body weight, daily gain and livability traits, respectively. Estimates of maternal (hM) and paternal (hP) heterosis were significant (P<0.05-0.01) and negative estimates for most the studied traits. Effects of direct recombination (rI) were positive and significant (P<0.01) for traits of BW4, BW8 and L4-8. Effects of maternal recombination (rM) were negative for most the studied traits and significant (P<0.01) only for traits of BW12, DG8-12 and DG4-12. Positive and significant (P<0.01) effect of rM on L8-12 (0.72%) was obtained. Effects of paternal recombination (rP) were negative for all the studied traits and significant (P<0.01) only for traits of BW12, DG4-8, DG8-12 and DG4-8. Epistatic effects of direct, maternal and paternal effects of additive x dominance and dominance x dominance are important on post-weaning growth and livability traits. Models of 3 and/or 4 are preferred to analysis crossbreeding data of rabbits, because these models included most of genetic components influencing traits. |
