Quantitative traits locus for milk production traits has been described on centromeric end of bovine chromosome 14. Reports name the acyl coA: diacylglycerol acyltransferase (DGAT1) gene as a potential candidate gene with dinucleotide substitution (AA to GC) in exon VIII which causes the change of lysine to alanine in amino acid (K232A).The aim of the present study was to estimate the frequency of DGAT1 K232A polymorphism in Iranian Holstein bulls as a potential quantitative trait locus (QTL) for marker assisted selection. Sample of 103 Holstein bulls from the Animal Breeding Center of Iran were genotyped for DGAT1 polymorphism (A and K allele). The PCR-RFLP technique was used to study the DGAT1 gene polymorphism. Frequency of KK, KA and AA genotypes were 0.59, 0.41 and zero respectively. The allele frequencies of the DGAT1 gene were 0.7961 and 0.2039 for K and A allele, respectively. The K allele was sequenced and registered in NCBI gene bank with EU075528 accession number. Manuscript profile

The aim of this study was to test the genotypes effect of DGAT1 gene on breeding value in Iranian Holstein milk production traits. For this purpose, 103 semen samples of registered bulls were collected and then genotyped for partial region of DGAT1 gene. The studied traits were milk yield (MY), fat yield (FY), protein yield (PY), fat percentage (FP) and protein percentage (PP). First lactation records of 43044 dairy cattle from 2000 to 2007 were used. The PCR-RFLP method was used for genotyping DGAT1 gene. The Hardy Weinberg equilibrium for allele and genotype frequencies was analyzed with Chi-square test using PoP-Gen software. Genetic parameters of studied traits were estimated by REML method under animal model with DFREML software. The breeding value of individual was predicted by BLUP method. Different genotype effect of 97 of 103 proven bulls on breeding value of milk production traits were investigated by GLM procedure of SAS (9.1) software.The mean of breeding value of proven bulls with different genotype were compare with Duncan test. The observed genotype frequency results showed KK (0.592), KA (0.408) and AA (zero) and the allele frequency obtained was K (0.7961) and A (0.2039). The KK genotype was confirmed by sequencing method and the K allele, with long of 411 bp, was registered in gene bank of NCBI with accession number EU077528. Estimated heritability of studied traits were 0.35 (0.02), 0.33 (0.02), 0.31 (0.017), 0.28 (0.02) and 0.27 (0.016) for MY, FY, PY, FP and PP, respectively. The average breeding values of MY, FY, PY, FP and PP were estimated as: 180.2 (28.8) kg, 3.7 (1.26) kg, 2.3 (1.06) kg, -0.036 (0.014) % and -0.03 (0.01) %, respectively. The average breeding value of MY for KA and KK genotypes were 288.8 and 109.6 kg, respectively and the difference was significant (P<0.01). The average breeding values of FY in bulls for KK and KA genotypes were 5.6 kg and 0.91 kg, respectively (P>0.05). The average breeding values of PY for KA and KK genotypes were 0.025 and 5.5 kg, respectively (P<0.05). Differences between means of breeding values for FP and PP were significant (P<0.05), these values for genotype KK and KA were -0.009% and -0.067% for fat and -0.016% and -0.059% for protein, respectively. Manuscript profile