The Egyptian Poultry Science AssociationEgyptian Poultry Science Journal1110-562344120240301HETEROTIC EFFECTS ON GROWTH TRAITS IN CROSSBREEDING EXPERIMENT BETWEEN APRI AND MOSHTOHOR RABBIT LINES11334726310.21608/epsj.2024.262872.1278ENAbdelwahab HKhattabDepartment of Animal and Poultry Breeding, Animal and Poultry Production Division, Desert Research Center, Ministry of Agriculture, El-Matareya 11753, Cairo, Egypt.Mahmoud MaghrabyIraqiAnimal production department, faculty of Agriculture, Benha University, Egypt0000-0001-5633-9191Maher KhalilDepartment of Animal Production, Faculty of Agriculture, Benha University0000-0002-6929-3011Emad AminDesert Rese. Center, Ministry of Agric., EgyptAyman G.EL NagarDepartment of Animal Production, Faculty of Agriculture, Benha University, Egypt0000-0001-7270-702XJournal Article20240114Five years crossbreeding experiment was preformed involving two synthetic rabbit lines of APRI (A) and Moshtohor (M) where bucks of APRI line and does of Moshtohor line were used to produce F<sub>1</sub> crossbreds (½A½M), followed by <em>inter-se</em> mating to obtain F<sub>2</sub> crossbreds (½A½M)<sup>2</sup>. A total number of 263 sires, 445 dams and 1998 kits were used to estimate heritabilities and predicted breeding values (PBV) for post-weaning body weights (BW) and daily weight gains (DG). The variance components estimated by Gibbs Sampling were used to solve the mixed model equations using the PEST software, getting the solutions for genetic groups' effects along with the solutions for other fixed effects. The crossbreeding effects in terms of direct additive genetic effects (G<sup>I</sup>), maternal effects (G<sup>M</sup>), direct heterosis (H<sup>I</sup>) and maternal heterosis (H<sup>M</sup>) were obtained according to Dickerson model using the procedure of Generalized Least Squares (GLS). Heritability estimates were low to moderate, ranging from 0.17 to 0.36 for BW and 0.09 to 0.23 for DG. The ratios of common litter effects were low to moderate and ranging from 0.04 to 0.16 for BW and 0.03 to 0.26 for DG. The interse cross (½A½M)<sup>2</sup> had the lowest ranges in PBVs for BW and DG relative to the other three genetic groups. The percentages of G<sup>I</sup> were in favor of M line by 0.2 to 2.3 % for BW and by 0.5 to 3.2 % for DG. Also, the percentages of G<sup>M </sup>were in favor of M line by 2.1 to 4.6 % for BW and by 1.6 to 9.4 % for DG. The estimates of H<sup>I</sup> were mostly significantly positive and ranging from 15.1 to 20.9 % for BW and 5.0 to 32.3 % for DG. Also, the estimates of H<sup>M</sup> were significantly positive by 6.8 to 11.0 % for BW and 0.7 to 18.1 % for DG. In practice, new synthetic rabbit lines could be established in Egypt using the APRI line as a sire-group and the Moshtohor line as a dam-group.https://epsj.journals.ekb.eg/article_347263_31c8a78e77038c3a612da42a25b933d7.pdf