Abstract：Ningxia which as an important beef cattle breeding province in China has responsibility to provide superior beef meat to whole country. The purpose of that was to study on genetic polymorphism of UCP3 gene in Simmental Hybrid Cattle (Bos taurus) and analyze their association with several growth traits to find genotype with fast growth rates that provided foundation for selecting and mating. PCR-SSCP and DNA sequencing were used to detect polymorphisms, contained DNAMAM, POPGENE1.31, PIC program, SAS software to calculate allelic frequencies, genotypic frequencies, PIC value, analysis different genotype association with growth traits (body weight, body height, body length, chest girth). Five SNPs on exons of bovine UCP3 gene were identified: G5465A, C7921G, A7953G, T8018C, T8162C, and caused transversion coding from alanine to threonine, proline to arginine, cysteine to arginine, tyrosine to histidine. The result of χ2 showed that two loci were deviated from the Hardy-Weinberg equilibrium. Genetic diversity analysis showed that the PIC values of two loci were 0.372 7, 0.370 4, which represented moderate polymorphism. The result of least square analysis showed that in exon3 fragment, the individuals with GA genotype showed better body sizes values in every months than GG genotype, the mutation of 5 465 bp G→A had significant effects in body weight, height and body length, especially in the later of growth stage, weight gain showed advantages obviously. In exon6 fragment, individuals with CC genotype showed better body sizes values than TC genotype, the mutation of 8 162 bpT→C had significant influence in body height and length from birth to 18 months (P＜0.05). Furthermore, analysis showed that body measurement traits (BW: body weight; BH: body height; BL: body length) of individuals with combined genotype GACC were higher than those of the other kinds of combinations. The effect of multi-loci combinations on BW were higher than those of single-marker locus. In hybrid simmental cattle, the variance analysis showed that the different genotypes of single or combined sites are significantly or extremely associated with its growth traits, combined genotype GACC had better BW, BL than single genotypes in different months. This study concluded the loci (5 465 bp, 8 162 bp) would be suitable for marker assisted selection (MAS) of Ningxia hybrid simmental cattle and GACC genotype may be the best one for the BW trait of Ningxia simmental hybrid cattle breeding.
