Calving traits of crossbred Brahman cows are associated with Heat Shock Protein 70 genetic polymorphisms.

Stress proteins and their genetic polymorphisms have been associated with decreased male and female fertility. Objectives were to: (1) identify single nucleotide polymorphisms (SNP) located in the promoter region of the bovine heat shock protein 70 (Hsp70) gene, and (2) evaluate associations between Hsp70 SNP, Julian calving date, and calving rates of crossbred Brahman cows. Specific primers were designed for PCR amplification of a 539 base segment of the bovine Hsp70 promoter (GenBank accession number M98823). Eleven single nucleotide polymorphisms were detected; one deletion at base position 895 (n=37), seven transitions (G1013A, n=2; G1045A, n=8; C1069T, n=4; A1096G, n=14; G1117A, n=12; T1134C, n=7; and T1204C, n=56), and three transversions (A1125C, n=53; G1128T, n=51; and C1154G, n=11). Cows that were homozygous for the minor allele at transversion site A1125C or G1128T had lesser (P<0.05) calving percentages than cows that were homozygous for the primary allele (48 vs. 75%). Homozygous and heterozygous deletion of cytosine at base 895 resulted in lower (P<0.05) calving percentages than homozygous cytosine cows (8, 50, 82%; respectively). In addition, homozygous deletion cows had the latest (P<0.05) Julian calving date. Eighteen Hsp70 promoter haplotypes were deduced, and seven of those haplotypes (n=37) included the deletion at base 895. Thirty-two cows had the haplotype consistent with the GenBank sequence and the remaining 30 cows had a SNP other than the deletion. Cows with deletion haplotypes had a lesser (P<0.05) calving percentage, and the latest (P<0.05) Julian calving date when compared with cows having other SNP haplotypes. Results from the present study suggest that the promoter region of the bovine Hsp70 gene is polymorphic and may be useful in selecting cows with a greater fertility.