Cortisol is a hormone associated with pain, fear, distress, or discomfort. We hypothesized that human interventions increase cortisol concentrations in plasma. Therefore, the objective of this study was to determine the concentration of cortisol in plasma before and after animals were subjected to routine on-farm and research procedures including artificial insemination, ruminal incubation, or esophageal tubing. Forty lactating Holstein cows were used in this study. Experimental treatments consisted of 4 interventions. Before any intervention, a first blood sample was collected from all cows. Following this bleeding, all cows were assigned to 1 of 4 treatments. A negative control treatment consisted of bleeding for a second time without any human intervention at least 30 min after the previous bleeding. Artificial insemination was performed by the herd managers from the Virginia Tech Dairy Complex. A rumen incubation treatment consisted of bleeding for a second time 30 min after opening the rumen cannula, inserting the operator's arm, and pulling ruminal contents out of the rumen for 2 min mimicking a ruminal in situ incubation, and placing back the cannula plug. An esophageal tubing treatment consisted of bleeding for a second time 30 min after inserting an esophageal tube into the esophagus and maintaining it inserted for 2 min mimicking a ruminal drenching procedure. Blood samples were collected from the coccygeal vessels. Cortisol concentration in plasma was measured by an independent laboratory using a chemiluminescence assay. The experiment was designed as a completely randomized design with repeated measures, where cow was the subject and the pre- and post-intervention bleeding were the repeated observations. The statistical model included the fixed effect of treatment, the random effect of cow, the fixed effect of time, the fixed effect of the treatment by time interaction, and the random residual error. According to Akaike's criterion, compound symmetry was utilized as the covariance structure for the repeated measures. Cortisol concentrations in plasma after the interventions did not differ from the cortisol concentrations in plasma before the interventions. Cows subjected to artificial insemination had greater cortisol concentrations than cow subjected to the other treatments. No interaction existed between treatment and time. Most cows subjected to insemination in a palpation rail had elevated cortisol concentrations before the intervention. Therefore, animal restraint seems to affect cortisol concentrations in plasma more than the actual human intervention. In conclusion, human interventions like artificial insemination, ruminal incubation, and esophageal tubing did not elevate the cortisol concentrations in the plasma of lactating dairy cattle under the conditions of this study.
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