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Title: Short Communication: Effect of heat stress during the dry period on gene expression in mammary tissue and peripheral blood mononuclear cells

Author
item TAO, SHA - University Of Florida
item Connor, Erin
item BUBOLZ, J. - University Of Florida
item THOMPSON, ISABELLA - University Of Florida
item DO AMARAL, BRUNO - University Of Florida
item HAYEN, M. - University Of Florida
item DAHL, GEOFFREY - University Of Florida

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2012
Publication Date: 12/26/2012
Citation: Tao, S., Connor, E.E., Bubolz, J.W., Thompson, I.M., Do Amaral, B.C., Hayen, M.J., Dahl, G.E. 2013. Short Communication: Effect of heat stress during the dry period on gene expression in mammary tissue and peripheral blood mononuclear cells. Journal of Dairy Science. 96(1):378-383.

Interpretive Summary: Heat stress during the dry period compromises mammary gland development, decreases future milk production, and impairs immune function of dairy cows. Our objective was to evaluate the effect of cooling heat-stressed cows during the dry period on gene expression related to development and function of the mammary gland and immune function of lymphocytes. Results indicated that cooling of heat-stressed cows during the dry period did not alter expression of the genes evaluated in the mammary gland relative to heat-stressed cows, but did reduce the expression of genes related to inflammation in lymphocytes. These results help to improve our understanding of physiological mechanisms contributing to the observed effects of heat stress on lactating dairy cows.

Technical Abstract: Heat stress (HT) during the dry period compromises mammary gland development, decreases future milk production, and impairs immune status of dairy cows. Our objective was to evaluate the effect of cooling HT cows during the dry period on gene expression of the mammary gland and lymphocytes. Cows were dried off 46 d before their expected calving and assigned to 2 treatments, HT or cooling (CL). Cows in the CL group were cooled with sprinklers and fans whereas HT cows were not. After parturition, all cows were housed in a free-stall barn with cooling. Lymphocytes were isolated at dry-off, -20, 2, and 20 d relative to calving from a subset of cows (HT, n = 9; CL, n = 10) and mammary biopsies were taken at the same intervals (HT, n = 7; CL, n = 6) for RNA extraction. Gene expression was assessed using a custom multiplex gene expression assay based on traditional reverse transcription-PCR. Genes involved in prolactin (PRL) signaling (PRL receptor long form [PRLR-L], PRLR short form [PRLR-S], suppressor of cytokine signaling 2 [SOCS2], SOCS3, IGF-II, IGF binding protein 5 [IGFBP5], and cyclin D1 [CCND1]), fatty acid (FA) metabolism (acetyl-CoA carboxylase alpha [ACACA] and lipoprotein lipase [LPL]), and IGF-I were evaluated in mammary tissue, and genes related to FA metabolism (ACACA, FA synthase [FASN], and LPL), cytokine production (IL6, IL8, and tumor necrosis factor [TNF]), and IGF-I were evaluated in lymphocytes. No differences (P > 0.05) were observed in PRL signaling or FA metabolism gene expression in the mammary gland. In lymphocytes, HT cows had greater IGF-I and TNF mRNA expression (P = 0.05) during the transition period relative to CL and up-regulated IL8 and down-regulated FASN mRNA expression at 2 d relative to calving. We conclude that cooling HT cows during the dry period alters expression of genes involved in cytokine production and lipid metabolism in lymphocytes.