Association between Single Nucleotide Ppolymorphism (SNP) in the Intronic Region of (C2239T) B4-Defensin Gene with Milk Production Traits and Somatic Cell Count in Holstein Cattle

Defensins are small antimicrobial peptides that play an important role in innate immunity. Therefore, their coding genes can be used as markers in selecting markers to help improve the economic quality of domestic animals. Therefore, the aim of this study was to investigate the relationship between C2239T SNP of the intron region of the beta-4-defensin gene with milk production traits and the somatic cell count in Holstein cows.

For this purpose, genomic DNA was extracted from 182 dairy cows. Then, using a suitable primer pairs, a 393 bp fragment from intron of bovine B4-defensin sequence (2100 to 2493) was amplified by the polymerase chain reaction. Then, the amplified fragment was screened by single strand conformation polymorphism (SSCP) and DNA sequencing methods. The associations between genotypes of the SNP with SCC and milk production traits were analyzed using the GLM procedure of SAS (9.1).

  A total of 3 distinct SSCP patterns (A, B and C) were observed which confirmed single nucleotide polymorphism (substitution of C to T) at position 2239 upon sequence analysis in the population. The frequencies of CC, CT and TT genotypes were 0.79, 0.13 and 0.08, respectively. No significant difference was observed between SNP genotypes and milk production traits and SCC. However, the genotypes were tended to associate with milk yield (p=0.10). The highest average milk yield and somatic cell count were found in the TT genotype, whereas the lowest ones for average milk yield and somatic cell count were CT a CC genotypes, respectively.

In this study, no significant relationship was observed between the identified genotypes with milk production traits and the number of body cells, but this relationship showed a significant tendency for the amount of daily milk production. The results also showed that TT and CT genotypes for this mutation had the highest and lowest milk production, respectively.