| This study was conducted to analysis fattening performance and the level of meat quality in 16 crossed herds of Red Steppe with Limousin, and 16 herds of pure Red steppe as control group,which were 10 months old, healthy, similar body size and weight. All of these cattle were fed according to mesotrophy standard in the same condition and management. Body size (body height, body length, chest depth, chest circumference), body weight and the growth data of these was determined during the fattening. And they were slaughtered after 301 days, and to measure the index of slaughter (rate of slaughter, net meat percentage, loin eye muscle) and meat quality (meat color, marbling grade, tenderness traits, the diameter of muscle fiber, drip loss, dehydration rate).Primers were designed according to bovine H-FABP sequence from GenBank, and PCR-SSCP was used for detecting bovine H-FABP 5'UTR polymorphisms in 16 crossed herds of Red Steppe with Limousin and also 16 Red Steppe individuals. Through statistics of the frequency of the allelic gene and genotype in the polymorphic site, the correlation of between different genotype and meat quality, which could provide some theory basis for further breeding. The result of fattening and slaughter showed that the difference of body height, body length and chest circumference were extremely significant (P<0.01) between the crossed herds of Red Steppe and Limousin and pure Red Steppe, between the crossed herds of Red Steppe with Limousin and pure Red Steppe the difference of body weight, weight gain, the average rate of slaughter and meat percentage of net meat were significant (p<0.05). But there were no significant differences in chest depth, daily weight, loin eye muscle, marbling grade, meat color, tenderness traits, the diameter of muscle fiber, drip loss and dehydration rate(P>0.05). The present study results showed that the improved varieties of Red Steppe growth velocity, the average rate of slaughter and meat percentage of net meat was obviously improved as well as keep the dominance of Red Steppe original tenderness traits, marbling grade, meat color in the process of crossbreeding and improvement, the crossing of Red Steppe with Limousin had the qualifications of the improved varieties beef cattle of domestic.The results of PCR-SSCP showed that bovine H-FABP gene of 5'- regulate region exist polymorphisms in Red Steppe and improved varieties, which is due to the insertion of base T in 136 bp and the transformation of G→A in 142 bp through sequencing. In improved varieties, the AB genotype frequency was 0.5, AA and BB genotype frequency all was 0.25, the A and B gene frequency all was 0.50. In Red Steppe, the frequency of AA, AB and BB genotype were 0.19, 0.50 and 0.31,respectly;The frequency of A and B allelic gene were 0.44 and 0.56, respectly.The correlation between different genotypes of 5'- regulate region SNP sites of H-FABP gene and meat quality of improved variety Red Steppe showed that A genotype was no effect to the tender trait.AA, AB and BB difference was extremely significant (P<0.01), but AB and BB genotype was no significant difference(P>0.05).However, the difference of between genotype with the other meat quality was not significant (P>0.05). The results showed that improved Red Steppe H-FABP had an important role in tenderness traits, but not the diameter of muscle fiber, drip loss, dehydration rate, meat color, marbling grade. H-FABP could be as the major gene or QTL for tenderness trait in improved Red Steppe herds, and BB genotype of 5'- regulate region as meat quality genetic marker had an important for further selection.
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