| Prolactin is a polypeptide hormone secreted by the anterior pituitary gland. PRL's biological activity consists of various roles in reproduction, lactation and immune functions. There is no genetic disease known currently to be linked to prolactin in cows. In view of this fact, we reasoned that genetic anomalies of bPRL genes could be related to somatic cell count (susceptibility to mastitis).The objective of this study is to analyse the correlations between PRL gene polymorphism and SCC. The study included a herd of 120 Chinese Holstein cows in first lactation. Four DNA fragments contain 4 Single Nucleotide Polymorphism (SNP) locis, PRL6216, PRL8398, PRL8377 and PRL8510 respectively, were amplified and identified the genotype by using the method of PCR-RFLP and CRS-RFLP. The results are as follow:1. Two alleles:A and B were found in the PRL6216 site and resulted in three genotypes named AA, AB and BB. The genotype frequency was the highest in AB (0.792), and the lowest in BB (0.025). BB cows were characterized by highest SCC(P< 0.05),fat content(P<0.05) and protein content but lowest daily milk yield and lactose content.2. In PRL8398, there were two alleles:A and G. The allele G, with a frequency of 0.754, was the dominant allele in the loci. AG cows were characterized by the highest milk yield (P< 0.05) and highest SCC.3. In PRL8377, with a frequency of 0.871, C alleles was dominant. Both SCC and daily milk yield are the highest in GG cows (P<0.05).4. In PRL8510, C and T allele were found and but no CT genotype was detected. CC genotype reached significant in milk yield compared to TT genotype (P<0.05). No significant difference in other traits was found including SCC.In conclusion, it is confirmed in this research that we can take PRL gene as candidate molecular marker and apply it to dairy cattle breeding using marker assisted selection. |
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