effect of stat1 variants on milk production traits in esfahan holstein cows

Stats are a family of latent transcription factors that reside in the cytoplasm of resting cells. the stat1 transcription factor gene located on the chromosome 2 at interval 60 to 63 cm. this factor upon stimulation with inf gamma, dimerizes and translocate to the nucleus where mediates transcriptional regulation. in this study, we estimated the allele and genotype frequencies of stat1/pag1 gene polymorphism and examined the association whit milk yield (305-day milk yield) and milk component (fat and protein percentage) traits. dna was isolated from 317 holstein cows of five different herds. a 314 bp fragment in stat1 gene was amplified and the animals were genotyped using rflp-pcr technique. seven genotypes including dd (89 animals), bb (25 animals), cc (11 animals), ac (15 animals), bc (9 animals), cd (164 animals) and bd (4 animals) were identified. frequencies of a, b, c, and d alleles were estimated to be 0.021, 0.101, 0.332 and 0.546, respectively. association of stat1/pag1 genotypes with percentage of fat in the milk was relatively high (p < 0.05); the dd genotype was superior to other groups. but corrected milk production for 305 days and protein percentage of the milk did not differ among all groups (p > 0.01). we concluded that this marker should be considered for milk component (fat percentage) selection in holstein dairy cows.