P
OLYMORPHISMS of the HSPA2 gene; a member of the bovine HSP 70 genes family, have been
associated with heat tolerance and reproductive performance in cattle. This study aims to
determine the role of genetic variation in the HSPA2 gene in Holstein cattle fertility. A total of 366
cows were classified into anestrum (37.7%) and fertile (62.3%) groups. Reproductive and productive
data were collected from farm records including age at first calving (AFC), calving interval (CI), calf
birth weight, milk yield, and days of milking. The genomic DNA of the cows was isolated, and PCR
SSCP was conducted to detect three fragments of the HSPA2 gene; 208, 317, and 393 bp. HSPA2 F1
revealed three different patterns, HSPA2 F2 was monomorphic, and HSPA2 F3 showed only two
patterns. Sequence analysis of HSPA2 F1 revealed three genotypes (CC, CT, and TT) with only one
SNP (C/T) as a transition single base substitution mutation located at 10:76649474 with the ID
rs377789074. Meanwhile, HSPA2 F3 showed two genotypes (CC and CT) with a synonymous SNP
(C/T) located at 10:76680875 with the ID rs132895070. The CT genotype of HSPA2 F1 and HSPA2
F3 genes was associated with a shorter calving interval and heavier calf birth weight in both fertile
and anestrum cattle. Our findings suggest that genetic variations in the HSPA2 gene could be utilized
as a molecular marker for genetic selection to enhance reproductive performance in both fertile and
anestrum Holstein cows raised in Egypt.