Study of Placental Lactogen gene polymorphism and its association with milk production traits in the Holstein cows

Placental Lactogen is a polypeptide hormone that is produced by the Placenta, also known as chorionic somatomammotropin hormone. It has both Growth Hormone and Prolactin activities on growth, lactation, and luteal steroid production. The objective of this study was to investigate the bovine Placental Lactogen (bPL) gene polymorphism of Holstein cows in Razavi Khorasan province. Blood samples were collected from 150 dairy cattle from six herds. DNA extraction was performed by salting out method. A fragment of 449 bp from intron 1 was amplified by the polymerase chain reaction and analyzed by single-strand conformation polymorphism to get the patterns of single-stranded DNA separated by native polyacrylamide gel electrophoresis and visualized by silver staining. Six genotypes were revealed with the frequencies of 0.283 (AA), 0.085 (AB), 0.292 (AC), 0.019 (CC), 0.292 (AD) and 0.029 (DD). The allele frequencies for A, B, C and D were 0.6179, 0.0425, 0.1651 and 0.1745, respectively.Chi-square test didnʹt confirm Hardy-Weinberg (H-W) equilibrium for this locus. Associations between polymorphisms and the traits studied were evaluated using the MIXED procedure of the SAS 9.1 software. Results showed that the polymorphism of the bPL gene is significantly is associated with fat percent (P=0.012).