Association of SNPs in the coding regions of CD4 gene with mastitis susceptibility and production traits in dairy cattle

Abstract

CD4 gene is reported to have significant role in various inflammatory conditions including mastitis. Therefore, the
current study was designed to screen out single nucleotide polymorphisms (SNPs) in the bovine CD4 gene and to
evaluate its effects on mastitis indicator and production traits. Total 201 milk and blood samples were collected from
dairy cattle maintained at government dairy farms of Khyber Pakhtunkhwa, Pakistan. Milk samples were used for DHI
test (milk composition and somatic cell count) and the blood for DNA extraction. SNPs were initially detected in the
pool DNA samples followed by screening in the whole cohort. The association of SNPs with the studied phenotypic
traits was analysed using the GLM procedure of SAS 9.4. Total four SNPs including three in exon 2 (SNP 1 A>C
rs110955838, SNP 2 T>G rs134722546, SNP 3 T>C rs135440143) and one in exon four (SNP4 G>A, rs134369392) were
revealed. The results showed that all the SNPs were significantly associated with frequency of clinical mastitis incidence
(P<0.05). Only SNP4 (G>A) was found to have significant association with annual milk yield (P<0.05). Furthermore,
breed and herd showed significant association with mastitis indicator and production traits (P<0.005). The parity wise
milk production results revealed highest annual milk yield in cattle with first parity (3649.2 L) followed by 2nd (3412.21
L), 3rd and above parities (3112.32 L). The present study suggests that CD4 gene should be considered as a candidate
gene and the identified SNPs could be worthy molecular markers for selection of dairy cattle with genetic resistance to
mastitis development.