|Do Amaral, Bruno|
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2012
Publication Date: 6/1/2012
Citation: Tao, S., Connor, E.E., Bubolz, J.W., Thompson, I.M., Do Amaral, B.C., Hayen, M.J., Dahl, G.E. 2012. Cooling of heat-stressed cows during the dry period alters lymphocyte but not mammary gland gene expression [abstract]. Journal of Animal Science. 90(suppl. 3):303. Paper No. T140. Interpretive Summary:
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 effects of cooling heat-stressed cows during the dry period on gene expression of the mammary gland and lymphocytes. Cows were dried off 46 d before their expected calving date and assigned to 2 treatments, HT or cooling (CL). Average temperature-humidity index during treatment was 76.6 for all cows. CL cows were cooled with sprinklers and fans that came on when ambient temperature exceeded 21.1 oC, whereas HT cows were not. Rectal temperature (RT) was measured twice daily and respiration rates (RR) recorded thrice weekly during the dry period. 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 expression assay based on traditional reverse transcription-PCR. Genes involved in prolactin (PRL) signaling (PRLR-L, PRLR-S, SOCS2 and 3, IGFII, IGFBP5, and Cyclin D1), fatty acid (FA) metabolism (ACC and LPL) and IGFI were evaluated in mammary tissue, and genes related to FA metabolism (ACC, FASN, and LPL), cytokine production (IL6, IL8, and TNFa) and IGFI were evaluated in lymphocytes. Data was analyzed by the PROC MIXED procedure of SAS. Compared with HT, CL cows had lower (P < 0.01) RT (39.4 vs. 39.0 oC) and RR (78 vs. 46 breath/min) in the afternoon before calving. No differences (P > 0.15) were observed in PRL signaling or FA metabolism gene expression in the mammary gland. In lymphocytes, HT cows had higher (P = 0.05) IGFI and TNFa mRNA expression during the transition period relative to CL and up-regulated (P < 0.05) IL8 and down-regulated (P = 0.01) FASN mRNA expression at 2 d relative to calving. We conclude that cooling HT cows during the dry period alters cytokine production and lipid metabolism in lymphocytes.