University of Guilan Animal Production Research 2252-0872 4 2 2015 08 23 Study of Lactoferrin gene single nucleotide polymorphism and its relation with milk somatic cells in crossbred cows of Guilan province Study of Lactoferrin gene single nucleotide polymorphism and its relation with milk somatic cells in crossbred cows of Guilan province 87 94 1270 FA M. Ayatollahi M.Sc. Student, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran S. H. Hosseini Moghaddam Assistant Professor, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran S. Z. Mirhosseini Professor, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran N. Ghavi Hossein-Zadeh Associate Professor, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran Journal Article 2015 09 12 Although Guilan province’s purebred cattle is low despite other regions, but crossbred cattle population are increasing.  Lactoferrin as a major mastitis resistant gene has substantial roles in dairy cattle’s udder tissue immune mechanisms. So, the effect of a known SNP on SCC of 100 crossbred cows with 50 percent father Holstein blood was studied in intron 6 of Lactoferrin gene. PCR product was a 301bp fragment that EcoR1 digestion produced three genotype including AA (301 bp), BB (201 and 100 bp) and AB (301, 201 and 100 bp). All three genotypes have been identified in the crossbred cows. Genotypes frequencies for AA, BB and AB were 41, 2 and 57%, that showed significant deviation from Hardy-Weinberg equilibrium (<em>P</em>˂0.01). Also, observed and expected heterozygosity was highly different. Frequency of A and B alleles were 69.5 and 30.5%, respectively and effective number of alleles (Ne) and Shannon’s index(I) were 1.74 and 0.62. Average SCC was 261×10³ per mL.Differences of SCS ofAB, AA and BB genotypes were not significant (<em>P</em>˂0.05). It is difficult to introduce A or B allele as marker for mastitis resistance, due to low frequency of BB genotype. Although Guilan province’s purebred cattle is low despite other regions, but crossbred cattle population are increasing.  Lactoferrin as a major mastitis resistant gene has substantial roles in dairy cattle’s udder tissue immune mechanisms. So, the effect of a known SNP on SCC of 100 crossbred cows with 50 percent father Holstein blood was studied in intron 6 of Lactoferrin gene. PCR product was a 301bp fragment that EcoR1 digestion produced three genotype including AA (301 bp), BB (201 and 100 bp) and AB (301, 201 and 100 bp). All three genotypes have been identified in the crossbred cows. Genotypes frequencies for AA, BB and AB were 41, 2 and 57%, that showed significant deviation from Hardy-Weinberg equilibrium (<em>P</em>˂0.01). Also, observed and expected heterozygosity was highly different. Frequency of A and B alleles were 69.5 and 30.5%, respectively and effective number of alleles (Ne) and Shannon’s index(I) were 1.74 and 0.62. Average SCC was 261×10³ per mL.Differences of SCS ofAB, AA and BB genotypes were not significant (<em>P</em>˂0.05). It is difficult to introduce A or B allele as marker for mastitis resistance, due to low frequency of BB genotype. https://ar.guilan.ac.ir/article_1270_9eaaecc8c889700f87f3a10fcad8c2e4.pdf