The Polymorphism Of Three Functional Genes And Their Relationship With Production Performances In Chinese Holstein And Yak

Polymorphism of three functional genes in 22 Tibetan yaks and 18 Holstein cows were studied by means of PCR-PFLP, and their relationship with 305-day milk yield, 305-day fat yield in Tibetan yaks was studied as well. Three candidate genes were growth hormone gene, k-casein gene and β-lactoglobulin gene. The results showed:There were polymorphisms in the restriction sites with Alu I in the fifth exon of GH gene of yak and Holstein, two alleles A and B were found in GH locus after the PCR product was digested with restriction enzyme Alu I . The frequencies of A allele and B allele in Tibetan yaks, were 0.909, 0.091. The frequencies in Holstein cows, were 0.917, 0.083. Two genotypes AA and AB, the frequencies of genotype AA and genotype AB in Tibetan yaks, were 0.820, 0.180. The frequencies in Holstein cows, were 0.840, 0.160. The genotype BB was not found, and allele frequencies between the two kinds of the subfamily Bovine were not significantly different (P>0.05).There were polymorphisms in the restriction sites with Pst I and Hindlll in the fourth exon of k-CN gene of Holstein. Two alleles A and B were found in k-CN locus after the PCR product was digested with restriction enzyme Pst I and Hindlll. The frequency of A allele in Holstein cows was 0.694. The frequency of B allele was 0.306. Three genotypes were AA, AB and BB, the frequency of genotype AA in Holstein cows was 0.444, the frequency of genotype AB was 0.500, the frequency of genotype BB was 0.056. In Tibetan yaks, there were not polymorphisms, and only B allele was found. There were not polymorphisms in β-Lg gene locus after the PCR product was digested with restriction enzyme Pvu II of Tibetan yaks and Holstein.The relationship between GH gene locus and 305-day milk yield, 305-day fat yield in Tibetan yaks was studied. Variation analysis showed: In Tibetan yaks, there was asignificant relationship between GH AA , AB genotypes and 305-day milk yield(P < 0.01), and there was not a significant relationship between GH AA, AB genotypes and 305-day fat yield(P > 0.05). So it was expected to develop a molecular genetic marker for selection using PCR-PFLP at GH gene site.The relationship between k-CN gene locus and 305-day milk yield, in Holstein cows was studied as well. Variation analsis showed: there was a significant relationship between k-CN AA, AB and BB genotypes and 305-day milk yield(P < 0.01), and there was not a significant relationship between k-CN AB, BB genotypes and 305-day fat yield(P > 0.05).Two linear models were used to test the relationship of k-CN and P-Lg gene loci on yield of milk and fat and protein, fat percentage and protein percentage in Holstein cows. Least square analysis showed: There was not significant effect of k-CN and P-Lg gene loci on yield of milk(P > 0.05). The only significant effect of genotype with the two models was the P-Lg loci on fat percentage(P < 0.1). The result of Dancun's multiple range test among different genotypes of each locus showed that the protein percentage of the individuals with P-Lg AA genotype was significantly lower than that of those with P-Lg AB or p-Lg BB genotype(P < 0.05).