Effects of Heat Shock Protein 70 Gene Polymorphism on Heat Resistance in Beef and Dairy Calves Based on Proliferation and Heat Shock Protein 70 Gene Expression in Peripheral Blood Mononuclear Cells and Hair Follicles.

The study objectives were to investigate the heat resistance using peripheral blood mononuclear cells (PBMCs) and hair follicles in beef and dairy calves based on heat shock protein (HSP) 70 genetic polymorphisms. The hair follicle samples from sixty calves (6 months old; 30 Korean native beef calves and 30 Holstein dairy calves) were collected for DNA extraction. The HSP70 single nucleotide polymorphism (SNP) was genotyped using a 5'-exonuclease activity (TaqMan) assay. In Study 1, PBMCs were isolated from 20 calves categorized by their HSP70 genotypes during a thermoneutral period: 10 Korean native beef calves (B-CC and B-C/-type) and 10 Holstein dairy calves (D-CC, D-C/-type). The PBMCs were then exposed to heat stress at 37 °C (control, CON) and 42 °C (heat stress, HS) for 3 h. Following this, the cells were returned to the 37 °C incubator at 0, 1, 3, 6, and 12 h for further recovery analysis. In Study 2, hair follicles were collected from 20 calves (six times every 30 days; threshold, mild, and moderate stress levels) and HSP70 gene expression was measured. Data were analyzed via two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test. The cell proliferation in the D-C/-group was significantly higher (