The effects of heat stress in Jersey, Hungarian Simmental
and Holstein-Friesian cows

. The effects of heat stress on the concentration of 70 kDa heat shock protein (HSP70) in plasma and saliva, plasma insulin concentration and some metabolic indices (plasma glucose, free fatty acids, beta-hydroxybutyrate and urea concentrations) were assessed in Holstein-Friesian, Hungarian Simmental and Jersey cows. The study included 30 animals from a farm breeding Holstein-Friesians, 30 from a Jersey farm and 30 from a farm keeping Simmentals (10 dry cows, 10 mid-lactating and 10 lactating cows from each farm, respectively). Sampling was performed under thermoneutral (spring) and heat stress (summer) conditions. Based on plasma HSP70 and insulin concentrations, Holstein cows were determined to be most susceptible to heat stress. No characteristic breed-related changes in metabolic indices were found. The results indicated the importance of heat load-reducing strategies in the Holstein-Friesian breed.