Single nucleotide polymorphisms associated with thermoregulation in lactating dairy cows exposed to heat stress.Dairy cows with increased rectal temperature experience lower milk yield and fertility.  Thermotolerance was assessed in lactating Holsteins during the summer by measuring rectal temperature (a direct measurement of body temperature regulation; n = 435), respiration rate (an indirect measurement of body temperature regulation, n = 450) and sweating rate (the major evaporative cooling mechanism in cattle, n = 455).  The association between genotype and thermotolerance was evaluated for 19 SNPs previously associated with rectal temperature from a genomewide analysis study (GWAS), four SNPs previously associated with change in milk yield during heat stress from GWAS, 2 candidate gene SNPs previously associated with rectal temperature and respiration rate during heat stress (ATPA1A and HSP70A) and 66 SNPs in genes previously shown to be associated with reproduction, production or health traits in Holsteins.  ARL6IP1 was associated with all three thermotolerance traits.  In conclusion, specific genetic markers responsible for genetic variation in thermoregulation during heat stress in Holsteins were identified. 
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