| The effects of genotypes of three candidate genes (bovine growth hormone gene, insulin-like growth factor-1 gene and insulin-like growth factor binding protein 3 gene) and 14 microsatellite loci on production traits were evaluated in Qinchuan cattle breed, and the population genetic characteristics and phylogenetic relationship of eight cattle breeds (including Qinchuan cattle, Chinese Holstein, Jiaxian Red cattle, Nanyang cattle, Luxi cattle, Bohai Black cattle, Yanbian cattle and Jinnan cattle)were analyzed. The main objects were to explore molecular genetic base of production traits in Qinchuan cattle and population genetic characteristics of eight Chinese yellow cattle breeds, so that molecular genetic markers for efficient selection of beef performance in Qinchuan cattle and construction of molecular genetic marker databases of Chinese yellow cattle breeds were provided primarily. The results were as follows:1. Relativity of polymorphisms of position 127(Iocus coding 127 amino acid) and position 172(locus coding 127 amino acid 172 amino acid) in bovine growth hormone gene with early growth traits of Qinchuan cattle:(1) In Qinchuan cattle population, there were two genotypes of A A and AC at position 127, their frequencies were 0.53 and 0.47, respectively, and this locus was not at Hardy-Weinberg equilibration (P <0.05). There were three genotypes of BB, BC and CC at position 172, and the frequencies were 0.642, 0.269, and 0.090, respectively, this locus was not at Hardy-Weinberg equilibration (P<0.01).(2) Birth weight, pin bone width and body length index of calves with AA genotype were higher than those of calves with genotype AC (P<0.05). The average weaning weight of calves with genotype AA was higher than that of calves with genotype AC for 13.26 kg, but both differences was not significant (P<0.05).(3) The average birth weight of calves with genotype BB was higher than that of calves with genotype BC and CC (P<0.05), The average beef purpose index (BPI) of calves with genotype CC was higher than that of calves with genotype BC and CC genotype(P<0.05). The average weaning weight of calves with CC genotype was higher than that of calveswith genotype BB for 21.32 kg and genotype BC for 24.42 kg (P<0.01).2.Relativity of polymorphic locus at Haelll restriction cleavage site in exon V an 3' flanking region of bovine growth hormone gene with slaughter traits of Qinchuan cattle:(l)There were three genotypes at this polymorphic locus, and the frequencies of genotype EE, EF, FF and allele E, F were 0.32, 0.56, 0.12, and 0.60, 0.40, respectively, this locus was at Hardy-Weinberg equilibration(P>0.05).(2) There were no significant effects of genotypes on live body weight, carcass weight, net beef weight, dressing percentage, net beef percentage and carcass beef percentage(P>0.05), while the average bone weight of individuals with genotype EE and EF was higher than that of FF genotype (P<0.05), and rib eye area of EE type individuals were higher than that of individuals with genotype EE and EF (P<0.05).(3) The average percentage of tenderloin, knuckle, top sirloin butt in carcass of individuals of genotype EE were higher than those in individuals of genotype EE and FF (P0.05).S.The effects of polymorphic locus at Haelll restriction cleavage site of Insulin-like growth factor binding protein 3 gene on slaughter traits of Qinchuan cattle:(1) In Qinchuan cattle population, there were three genotypes at this polymorphic locus, and the frequencies of genotypes and alleles were 0.70, 0.28, 0.02 and 0.84, 0.16, this locus was at Hardy-Weinberg equilibration(P>0.05), but no individuals with genotype BB were detected among slaughtered Qinchuan cattle.(2) The average live weight, carcass weight, and bone weight of the individuals with genotype AA and AB were slightly different, but it was not significantly (P>0.05), dressing percentage and net beef percentage of the individuals with genotype AA were slightly higher than those of individuals with genotype AB(P>0.05), while rib eye area of individuals...
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