Mostafa Sadeghi - Department of Animal Science, Faculty of Agricultural Science and Engineering, University College of Agriculture and Natural Resources (UTCAN), University of Tehran, Karaj, Iran.
Mahdi Mokhber - Department of animal science, Faculty of Agriculture, Urmia University, Urmia, Iran.
Mohammad Moradi Shahrbabak - Department of Animal Science, Faculty of Agricultural Science and Engineering, University College of Agriculture and Natural Resources (UTCAN), University of Tehran, Karaj, Iran.

A total of 130 Iranian proved Holstein were used to study polymorphisms of the pituitary transcription factor (Pit-1) gene. The genotypes were detected by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). The allelic frequencies were 0.321 and 0.679 for A and B alleles of Pit-1 gene, respectively. There was significant association (P<0.05) between protein yield and observed Pit1-HinfI genotypes. No significant association (P> 0.05) was found between Pit1- HinfI with other milk production traits. These results revealed that detected Pit1-HinfI genotypes had significant effects on milk protein yield and can be used as a marker for this trait. It may be necessary to carry out further studies with larger sample sizes to make a clear relationship between mentioned gene variants and milk production traits.

Pit-1, Iranian proved bulls, Polymorphisms.