Abstract: heat stress affects feed intake, milk production, and endocrine status in dairy cows. The temperature-humidity index (THI) is employed as an index to evaluate the degree of heat stress in dairy cows. However, it is difficult to ascertain whether THI is the most appropriate measurement of heat stress in dairy cows. This experiment was conducted to investigate the effects of heat stress on serum insulin, adipokines (leptin and adiponectin), AMP-activated protein kinase (AMPK), and heat shock signal molecules (heat shock transcription factor (HSF) and heat shock proteins (HSP)) in dairy cows and to research biomarkers to be used for better understanding the meaning of THI as a bioclimatic index. To achieve these objectives, two experiments were performed. The first experiment: eighteen lactating Holstein dairy cows were used. The treatments were: heat stress (HS, THI average=81.7, n=9) and cooling (CL, THI average=53.4, n=9). Samples of HS were obtained on August 16, 2013, and samples of CL were collected on April 7, 2014 in natural conditions. The second experiment: HS treatment cows (n=9) from the first experiment were fed for 8 weeks from August 16, 2013 to October 12, 2013. Samples for moderate heat stress, mild heat stress, and no heat stress were obtained, respectively, according to the physical alterations of the THI. Results showed that heat stress significantly increased the serum adiponectin, AMPK, HSF, HSP27, HSP70, and HSP90 (P<0.05). Adiponectin is strongly associated with AMPK. The increases of adiponectin and AMPK may be one of the mechanisms to maintain homeostasis in heat-stressed dairy cows. When heat stress treatment lasted 8 weeks, a higher expression of HSF and HSP70 was observed under moderate heat stress. serum HSF and HSP70 are sensitive and accurate in heat stress and they could be potential indicators of animal response to heat stress. We recommend serum HSF and HSP70 as meaningful biomarkers to supplement the THI and evaluate moderate heat stress in dairy cows in the future.

热应激对奶牛血液中胰岛素、脂肪因子、AMP激活蛋白激酶和热休克信号分子的影响

[1]Ailhaud, G., 2006. Adipose tissue as a secretory organ: from adipogenesis to the metabolic syndrome. C. R. Biol., 329(8):570-577.

[2]Armstrong, D., 1994. Heat stress interaction with shade and cooling. J. Dairy Sci., 77(7):2044-2050.

[3]Beckham, J.T., Mackanos, M.A., Crooke, C., et al., 2004. Assessment of cellular response to thermal laser injury through bioluminescence imaging of heat shock protein 70. Photochem. Photobiol., 79(1):76-85.

[4]Berman, A., 2005. Estimates of heat stress relief needs for Holstein dairy cows. J. Anim. Sci., 83(6):1377-1384.

[5]Bernabucci, U., Basiricò, L., Morera, P., et al., 2009. Heat shock modulates adipokines expression in 3T3-L1 adipocytes. J. Mol. Endocrinol., 42(2):139-147.

[6]Bernabucci, U., Biffani, S., Buggiotti, L., et al., 2014. The effects of heat stress in italian Holstein dairy cattle. J Dairy Sci., 97(1):471-486.

[7]Bohmanova, J., Misztal, I., Cole, J.B., 2007. Temperature-humidity indices as indicators of milk production losses due to heat stress. J. Dairy Sci., 90(4):1947-1956.

[8]Buffington, D., Collazo-Arocho, A., Canton, G., et al., 1981. Black globe-humidity index (BGHI) as comfort equation for dairy cows. Trans. ASAE, 24(3):0711-0714.

[9]Cheng, J.B., Bu, D.P., Wang, J.Q., et al., 2014. Effects of rumen-protected γ-aminobutyric acid on performance and nutrient digestibility in heat-stressed dairy cows. J. Dairy Sci., 97(9):5599-5607.

[10]Collier, R., Collier, J., Rhoads, R., et al., 2008. Invited review: genes involved in the bovine heat stress response. J. Dairy Sci., 91(2):445-454.

[11]Corton, J.M., Gillespie, J.G., Hardie, D.G., 1994. Role of the AMP-activated protein kinase in the cellular stress response. Curr. Biol., 4(4):315-324.

[12]Dikmen, S., Hansen, P.J., 2009. Is the temperature-humidity index the best indicator of heat stress in lactating dairy cows in a subtropical environment? J. Dairy Sci., 92(1):109-116.

[13]Feder, M.E., Hofmann, G.E., 1999. Heat-shock proteins, molecular chaperones, and the stress response: evolutionary and ecological physiology. Annu. Rev. Physiol., 61(1):243-282.

[14]Frederich, M., O'Rourke, M.R., Furey, N.B., et al., 2009. AMP-activated protein kinase (AMPK) in the rock crab, Cancer irroratus: an early indicator of temperature stress. J. Exp. Biol., 212(Pt 5):722-730.

[15]Gaughan, J., Bonner, S., Loxton, I., et al., 2013. Effects of chronic heat stress on plasma concentration of secreted heat shock protein 70 in growing feedlot cattle. J. Anim. Sci., 91(1):120-129.

[16]Gaughan, J.B., Mader, T.L., Holt, S.M., et al., 2008. A new heat load index for feedlot cattle. J. Anim. Sci., 86(1):226-234.

[17]Hansen, P., 2004. Physiological and cellular adaptations of zebu cattle to thermal stress. Anim. Reprod. Sci., 82-83:349-360.

[18]Hardie, D.G., Scott, J.W., Pan, D.A., et al., 2003. Management of cellular energy by the AMP-activated protein kinase system. FEBS Lett., 546(1):113-120.

[19]Kavanagh, K., Flynn, D.M., Jenkins, K.A., et al., 2011. Restoring HSP70 deficiencies improves glucose tolerance in diabetic monkeys. Am. J. Physiol. Endocrinol. Metab., 300(5):E894-E901.

[20]Lee, W.C., Wen, H.C., Chang, C.P., et al., 2006. Heat shock protein 72 overexpression protects against hyperthermia, circulatory shock, and cerebral ischemia during heatstroke. J. Appl. Physiol., 100(6):2073-2082.

[21]Li, G., Ali, I.S., Currie, R.W., 2006. Insulin induces myocardial protection and Hsp70 localization to plasma membranes in rat hearts. Am. J. Physiol. Heart Circ. Physiol., 291(4):H1709-H1721.

[22]Li, Q.L., Ju, Z.H., Huang, J.M., et al., 2011. Two novel SNPs in HSF1 gene are associated with thermal tolerance traits in Chinese Holstein cattle. DNA Cell Biol., 30(4):247-254.

[23]Liu, C.T., Brooks, G.A., 2012. Mild heat stress induces mitochondrial biogenesis in C2C12 myotubes. J. Appl. Physiol., 112(3):354-361.

[24]Malvoisin, E., Livrozet, J.M., El Hajji-Ridah, I., et al., 2009. Detection of AMP-activated protein kinase in human sera by immuno-isoelectric focusing. J. Immunol. Methods, 351(1-2):24-29.

[25]MOA (Ministry of Agriculture of China), 2004. Feeding Standard of Dairy Cattle, NY/T 34-2004. MOA, Beijing, China.

[26]Marai, I., El-Darawany, A., Fadiel, A., et al., 2007. Physiological traits as affected by heat stress in sheep— a review. Small Ruminant Res., 71(1-3):1-12.

[27]Morera, P., Basirico, L., Hosoda, K., et al., 2012. Chronic heat stress up-regulates leptin and adiponectin secretion and expression and improves leptin, adiponectin and insulin sensitivity in mice. J. Mol. Endocrinol., 48(2):129-138.

[28]O'brien, M., Rhoads, R., Sanders, S., et al., 2010. Metabolic adaptations to heat stress in growing cattle. Domest. Anim. Endocrinol., 38(2):86-94.

[29]Page, T.J., Sikder, D., Yang, L., et al., 2006. Genome-wide analysis of human HSF1 signaling reveals a transcriptional program linked to cellular adaptation and survival. Mol. Biosyst., 2(12):627-639.

[30]Park, H., Han, S., Oh, S., et al., 2005. Cellular responses to mild heat stress. Cell. Mol. Life Sci., 62(1):10-23.

[31]Patir, H., Upadhyay, R., 2010. Purification, characterization and expression kinetics of heat shock protein 70 from Bubalus bubalis. Res. Vet. Sci., 88(2):258-262.

[32]Rensis, F.D., Scaramuzzi, R.J., 2003. Heat stress and seasonal effects on reproduction in the dairy cow—a review. Theriogenology, 60(6):1139-1151.

[33]Rhoads, M., Rhoads, R., Vanbaale, M., et al., 2009. Effects of heat stress and plane of nutrition on lactating Holstein cows: I. production, metabolism, and aspects of circulating somatotropin. J. Dairy Sci., 92(5):1986-1997.

[34]Rhoads, R.P., Baumgard, L.H., Suagee, J.K., et al., 2013. Nutritional interventions to alleviate the negative consequences of heat stress. Adv. Nutr., 4(3):267-276.

[35]St-Pierre, N., Cobanov, B., Schnitkey, G., 2003. Economic losses from heat stress by us livestock industries. J. Dairy Sci., 86:E52-E77.

[36]Tanaka, K., Jay, G., Isselbacher, K.J., 1988. Expression of heat-shock and glucose-regulated genes: differential effects of glucose starvation and hypertonicity. Biochim. Biophys. Acta, 950(2):138-146.

[37]Trinklein, N.D., Murray, J.I., Hartman, S.J., et al., 2004. The role of heat shock transcription factor 1 in the genome-wide regulation of the mammalian heat shock response. Mol. Biol. Cell, 15(3):1254-1261.

[38]Wang, S., Diller, K.R., Aggarwal, S.J., 2003. Kinetics study of endogenous heat shock protein 70 expression. J. Biomech. Eng., 125(6):794-797.

[39]West, J., 2003. Effects of heat-stress on production in dairy cattle. J. Dairy Sci., 86(6):2131-2144.

[40]Wheelock, J.B., Rhoads, R.P., Vanbaale, M.J., et al., 2010. Effects of heat stress on energetic metabolism in lactating Holstein cows. J. Dairy Sci., 93(2):644-655.

[41]Yamauchi, T., Kamon, J., Minokoshi, Y., et al., 2002. Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase. Nat. Med., 8(11):1288-1295.