A simple crossbreeding experiment was conducted between males of APRI line (A) and females of Moshtohor line (M) rabbits. These two lines are new synthetic lines raised in Egypt for meat production. APRI line was formed in the experimental stations belonging to the Animal Production Research Institute (APRI), Agricultural Research Center, Ministry of Agriculture, Egypt, while Moshtohor line was established in the Faculty of Agriculture, Benha University, Egypt. The crossbreeding scheme was performed during two consecutive production seasons (2015/2016 and 2016/2017) at the rabbitry of the Animal Production Department, Faculty of Agriculture, Benha University. The molecular analyses were conducted at the Central Laboratory, Faculty of Veterinary Medicine, Benha University. The main objectives of the present study were: (1) to estimate variance components, heritability, direct additive, maternal additive, and direct heterotic effects for post-weaning body weights at (4, 6, 8, 10 and 12 weeks of age) and daily weight gains (during the intervals 4-6, 6-8, 8-10 and 10-12 weeks) and semen quality traits (ejaculate volume, pH semen, sperms motility, sperms concentration, live and dead sperms, normal and abnormal sperms), (2) to use the PCR-RFLP technique to genotype the C>T SNP located in the promoter region of GH gene in five genetic groups of rabbits (APRI, Moshtohor, ½A½M, V line and Sinai Gabali) and (3) to detect the polymorphic associations between (C>T( SNP genotypes of GH gene and growth or semen quality traits. A total number of 1201 weaned rabbits fathered by 179 sires and mothered by 261 dams were used in quantitative and molecular analyses of growth traits, while a total of 1050 ejaculates collected from 149 bucks were used in semen quality traits. For detecting the associations between genotypes of GH gene and growth or semen traits, the method of Generalized Least Squares (GLS) was used. The most relevant results of this study could be summarized as follows:
Quantitative genetic analyses for growth and semen quality traits:
• Estimates of heritability for body weights and gains were mostly low or moderate and ranging from 0.06 to 0.18 for estimates obtained from VCE software and 0.09 to 0.18 for estimates obtained from TM software. The estimates for semen quality traits resulted from TM software were very low and ranged from 0.01 to 0.03, while those estimated by VCE6 software were relatively moderate and ranged from 0.12 to 0.20.
• The generalized least square solutions of direct additive effects (GI) were significantly (P |
