The present study was conducted to identify single nucleotide variations in exon 3 region
of the bovine Toll-Like Receptor gene (TLR4) associated with somatic cell score (SCS) in crossbred
cattle of Kerala using polymerase chain reaction-single stranded conformational polymorphisms
(PCR-SSCP) technique. Blood samples were collected from 200 lactating crossbred cattle in
different farms of Kerala Veterinary and Animal Sciences University (KVASU) and field centres of
ICAR- FPT scheme, KVASU. Genomic DNA was isolated and polymorphisms were identified by
SSCP analysis. The 231 bp fragment of exon 3 in TLR4 gene was found to polymorphic and two
genotypes viz. CC and CD were obtained with frequencies 77 per cent and 23 per cent respectively.
The frequencies of C and D allele in crossbred were found to be 0.88 and 0.12. On sequencing,
C to T transition had led to one non-synonymous change at 2021th position of ORF. Cattle with CC
genotype were associated with significantly lower SCS (p≤0.05) as compared to CD genotype. The
association between TLR4 polymorphism and SCS described in this study suggests the possible
role of SNP during mastitis infection. Thus, could be employed as a useful marker for genetic
selection to promote mastitis resistance in dairy cattle
