Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2009
Publication Date: 7/23/2009
Publication URL: http://hdl.handle.net/10113/36564
Citation: Amaral, B.C., Connor, E.E., Tao, S., Hayen, J., Bubolz, J., Dahl, G.E. 2010. Heat stress abatement during the dry period influences prolactin signaling in lymphocytes. Domestic Animal Endocrinology. 38(1):38-45. Interpretive Summary: Heat stress of dairy cattle can have detrimental effects on feed intake, milk yield, and immunity, all of which affect dairy efficiency. The mechanism of the effects of heat stress on immune cell function is not clear. In this study, the effect of reducing heat stress in dairy cows during the period just prior to calving (dry period) on immune cell function and gene expression was examined. Results indicated that the negative effects of heat stress on immune cell function may be mediated by changes in prolactin signaling. Thus, providing cooling during the dry period may improve health in dairy cattle during lactation.
Technical Abstract: Heat stress perturbs PRL release and affects dairy cow lactational performance and immune cell function. We hypothesized that greater PRL concentration in plasma of heat-stressed cows would decrease expression of PRL-R mRNA and increase mRNA expression of suppressors of cytokine signaling (SOCS) in lymphocytes, altering their cytokine production. To test this hypothesis, multiparous Holstein cows were dried off 46 d before their expected calving date and assigned randomly to heat stress (HT; n = 9) or cooling (CL; n = 7) during the entire dry period. Lymphocytes were isolated from cows at -46, -20, +2 and +20 d relative to expected calving date and mRNA expression of PRL-R, SOCS-1, SOCS-2, SOCS-3, CIS, and HSPA5, and housekeeping genes HMBS, ATP5B, and RPS9 was analyzed by quantitative real-time RT-PCR. Measurement of lymphocyte proliferation indicated that lymphocytes of CL cows proliferated more than those from HT cows, expressed more PRL-R mRNA, and less SOCS-1 and SOCS-3 mRNA compared to HT cows. Further, lymphocytes from CL cows produced more TNF-a than those from HT cows. These results suggest that changes in PRL-signaling pathway genes during heat stress are associated with differential cytokine secretion by lymphocytes, and may regulate lymphocyte proliferation in dairy cows.