Abstract
BackgroundThe warming climate is causing livestock to experience heat stress at an increasing frequency. Holstein cows are particularly susceptible to heat stress because of their high metabolic rate. Heat stress negatively affects immune function, particularly with respect to the cell-mediated immune response, which leads to increased susceptibility to disease. Cattle identified as having enhanced immune response have lower incidence of disease. Therefore, the objective of this study was to evaluate the impact of in vitro heat challenge on blood mononuclear cells from dairy cattle, that had previously been ranked for immune response, in terms of heat shock protein 70 concentration, nitric oxide production, and cell proliferation.ResultsBlood mononuclear cells from dairy cattle classified as high immune responders, based on their estimated breeding values for antibody and cell-mediated responses, produced a significantly greater concentration of heat shock protein 70 under most heat stress treatments compared to average and low responders, and greater cell-proliferation across all treatments. Similarly, a trend was observed where high responders displayed greater nitric oxide production compared to average and low responders across heat treatments.ConclusionOverall, these results suggest that blood mononuclear cells from high immune responder dairy cows are more thermotolerant compared to average and low immune responders.
Highlights
The warming climate is causing livestock to experience heat stress at an increasing frequency
HSP70 concentration decreased to its lowest concentration after Heat stress 2 (HS2) (8.45 ng/ ml), with both Heat stress 1 (HS1) (p = 0.02) and 18-h post HS1 (9.54 ng/ml, p = 0.03) having significantly greater HSP70 concentration compared to HS2
Cell proliferation at TN was significantly greater than cell proliferation after HS2 (p = 0.001) for low responders and not significant, cell proliferation at TN was higher than cell proliferation after HS1
Summary
The warming climate is causing livestock to experience heat stress at an increasing frequency. Heat stress negatively affects immune function, with respect to the cell-mediated immune response, which leads to increased susceptibility to disease. Over the years, are contributing to climate change This is because greenhouse gases trap energy, that is emitted from the earth’s surface, in the lower atmosphere not allowing this energy to be emitted back into space [1]. Studies have shown heat stress causes an increase in the incidence of several different diseases in dairy cattle, including metabolic disorders, as well as mastitis [5, 6]. One of the effects of heat stress on the adaptive immune response is disruption of the balance between T-helper 1 (TH1) and T-helper 2 (TH2) responses, causing a shift towards a TH2 response [4] This bias can lead to impaired cell-mediated immune response (CMIR). If lymphocyte proliferation is reduced it is more difficult for cattle to defend against invading pathogens
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