| Mastitis is the most serious disease in dairy industry. There are so many factors causing the disease, and genetic factors play an important role. So at present seeking for mastitis resistant genes or molecular markers for MAS(Marker-Assisted Selection) becomes the hot spot in bovine disease resistance research.In this reseach totally 300 Chinese Holstein blood samples were used to extract genomic DNA. Molecular biology experimental technology was applied to analyze the polymorphisms of TLR4, CXCR2 and FEZL gene. The association between the candidate genes and mastitis was analyzed using least square method in the way of GLM by SAS sofeware.To detect the DNA polymorphism of bovine TLR4 gene, a 321bp segment of TLR4 gene exon III was analyzed by PCR-RFLP, results showed that a mutation exist in the amplified production, which can be recognized by restriction endonuclease Bbv12I and resulted in a change of amino acid (Thr into Ile). SAS sofeware statistical results indicated that SCS were significantly affected by different genotypes (P<0.05). The SCS LSM of genotype CC, CT and TT were 4.58, 4.58 and 3.80 respectively, Genotype TT individuals had better mastitis resistance.PCR-SSCP and DNA sequencing technology was used to detect the polymorphism of CXCR2 gene, results showed that, there were six SNPs called +612, +684, +777, +855, +858 and +861 in that 777bp amplification fragment. Linkage disequilibrium analyze result showed the six loci were mutually independent in the heredity. The degree of correlation for +684 and +861, +777 and +858 were 0.635 and 0.541 respectively,so they can represent each other well. SAS sofeware statistical results indicated: the two SNPs +684 and +855 had no significant effects on SCS(P>0.05).Different genotypes in +612 locus had significant effect on SCS(P<0.05), SCS LSM of genotype AA, AG and GG were 4.43, 4.75 and 4.55 respectively, genotype AA individuals had better mastitis resistance. Different genotypes in +777 locus had significant effect on SCS(P<0.05), SCS LSM of genotype CG and GG were 4.69 and 4.41 respectively, genotype GG individuals had better mastitis resistance.Non-denatured PAGE(Polyacrylamide Gle Electorphoresis) method was used to detect the delete mutation of FEZL gene, result showed that the GCC deletion did not exist in this population.Least square analysis showed that herd, parity had significant effect on SCS. The herd 2had the highest SCS of 5.08, and herd 5 was the lowest. SCS increased with the parityexcept the six parity group. Calving season had no significant effects on SCS(P>0.05) .SCS of calving season was low in spring and winter, but high in summer andautumn.Least square analysis showed that dairy herd, parity and calving season had significant effect on milk yield (P<0.01). The LSM of milk yield increased with parity. Milk yield was the lowest when calving in summer,and highest in winter. The different levels of SCC had no significant effects on milk yield(P>0.05),but milk yiled declined with the SCC increased.The milk fat percentage LSM difference was extremely significant in dairy herds, parities and SCC levels (P<0.01), it was 4.38% in the third herd and higher than others. The fat ratio had a decreasing tendency with the parity increased except the fourth, and enhanced with SCC. Calving season had no significant effect on it (P>0.05).The milk protein rate LSM difference was extremely significant in dairy herds, parities and SCC levels (P<0.01),and it increased with SCC. Protein rate was high calving in summer and autumm, and low in spring and winter. Parity had no significant effect on it(P>0.05). |
PDF Full Text Request