Study On Candidate Genes Related To Milk Production Traits In Holstein Cows

To detect the polymorphisms of PPARGC1A,FASN and STAT5A gene in Holstein cows, CAPS (PCR-RFLP), PCR-PAGE, PCR-SSCP, sequence analysis and gene cloning were used. The relation between the polymorphisms and milk production traits (milk yield at 305d, protein percentage, fat percentage, lactose percentage and dry matter percentage) was also studied to provide a scientific basis for marker-assisted selection of milk production traits in cows. The results were as follows.1) The products amplified by primers P1, P2, P16 and P18 displayed polymorphisms in PPARGC1A gene. For primer P1, three genotypes (CC, CT and TT) were detected at C85330T site in Holstein cows by digesting the PCR products with restriction endonuclease Haeâ…¢, and the frequency of CC/CT/TT was 0.621/0.326/0.053, respectively. Least squares mean of fat percentage for TT or CT was significantly higher than that for CC(P<0.05), the difference of the least squares mean for fat percentage was not significant between TT and CT (P>0.05).For primer P2, three genotypes (AA, AC and CC) were detected at A103592C site in Holstein cows by digesting the PCR products with restriction endonuclease Nheâ… , and the frequency of AA/AC/CC was 0.430/0.444/0.126, respectively. Least squares mean of protein percentage for AA or AC was significantly higher than that for CC (P<0.05), the difference of the least squares mean for protein percentage was not significant between AA and AC (P>0.05). For 2632delCTTT mutation site, three genotypes (EE, EF and FF) were detected in Holstein cows, and the frequency of EE/EF/FF was 0.742/0.237/0.021, respectively. The differences of the least squares means for the five milk production traits between EE, EF and FF were not significant (P>0.05). For primer P18, three genotypes (GG, GH and HH) were detected at T84064C site in Holstein cows, and the frequency of GG/GH/HH was 0.770/0.218/0.012, respectively. The differences of the least squares means for the five milk production traits between GG, GH and HH were not significant (P>0.05).2) Only the products amplified by primers P3 and P8 displayed polymorphisms. For P3, three genotypes (AA, AB and BB) were detected at G15028A site in Holstein cows, and the frequency of AA/AB/BB was 0.757/0.233/0.010, respectively. For P8, three genotypes (CC, CD and DD) were detected at G16923A site in Holstein cows, and the frequency of CC/CD/DD was 0.489/0.425/0.086, respectively. The two sites were all in Hardy-Weinberg equilibrium. Association analysis showed that the DD genotype of g.16923G>A was associated with a significant increase in fat percentage (P<0.05).3) The products amplified by primers P1 and P2 displayed polymorphisms. For P1, three genotypes (AA, AG and GG) were detected at G14217A site in Holstein cows, and the frequency of AA/AG/GG was 0.252/0.486/0.262 respectively. For 17266indelCCT mutation site, three genotypes (CC, CT and TT) were detected in Holstein cows, and the frequency of CC/CT/TT was 0.751/0.234/0.015, respectively. The two sites were all in Hardy-Weinberg equilibrium. Association analysis showed that, for P1, the AG and GG genotype were associated with a significant increase in protein percentage (P<0.05). However, for P2, the TT and CT genotype were associated with a significant increase in milk yield at 305 d (P<0.05), and the CC and CT genotype were associated with a significant increase in fat percentage (P<0.05).