Author
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Stellflug, John |
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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/18/2006 Publication Date: 6/1/2006 Citation: Stellflug, J.N. 2006. Comparison of cortisol, luteinizing hormone, and testosterone responses to a defined stressor in sexually inactive rams and sexually active female-oriented and male-oriented rams. Journal of Animal Science. 84:1520-1525. Interpretive Summary: The current study was undertaken to determine whether a defined stressor (restraint) would differentially affect cortisol, LH, and testosterone in sexually inactive and sexually active female-oriented and male-oriented rams allowing for differentiation among behavioral classes of rams. Restraint stress increased cortisol, caused minimal change in LH, and decreased testosterone similarly in sexually inactive and sexually active female-oriented and male-oriented rams. Thus, characterizing cortisol, LH, and testosterone after restraint stress does not provide a means to differentiate among sexually inactive and sexually active female-oriented and male-oriented rams. Technical Abstract: The objective of this study was to determine whether the effect of restraint stress on cortisol, LH, and testosterone varied among sexually inactive and sexually active female- and male-oriented rams. Restraint stress or no stress was imposed on sexually inactive (n = 7) and sexually active female- (n = 17) and male-oriented (n = 6) rams in a 2 x 3 factorial arrangement. Rams were assigned to restraint or control within each classification. Rams were habituated to wearing halters and being tethered in separate pens permitting visual, vocal, and olfactory contact with adjacent rams for 7 d before treatment. After 1 d of habituation, rams were fitted with jugular catheters that were checked twice daily for patency. For restraint stress, rams were laid on their side with legs tied for 1 h. For no stress, rams were tethered with halters and leads, but not tied on their side. On treatment day, blood was collected at 30-min intervals for 3 h followed by 15-min intervals for 1 h before restraint, during 1-h restraint, and for 1 h after liberation from 1-h restraint stress. Then blood was collected at 30-min intervals for an additional 2 h. Blood was collected at similar intervals from controls. Control rams were isolated from stressed rams. Cortisol, LH, and testosterone were measured using RIA. Mixed model analyses with repeated measures were used on transformed data. Average prestress data was used as a covariate. Cortisol increased (P < 0.01) within 15 min after restraint and remained increased until 90 min after liberation from 1-h of restraint stress. In contrast, cortisol remained unchanged at 5 ng/mL in controls. Cortisol did not differ over time among ram classes and treatment x ram class x time interaction was not significant. For LH, stress treatment x ram class x time interaction (P < 0.001) was related to increases in sexually inactive and male-oriented control rams compared to no increases in stressed rams. For testosterone, stress treatment x time interaction (P < 0.05) was related to testosterone remaining stable at 18 to 25 ng/mL in controls over time in contrast to decreasing (P < 0.05) to 15.8 +/- 2.9 ng/mL within 90 min and to 8.2 +/- 1.1 ng/mL at 4 h after onset of restraint. We conclude that restraint stress increased cortisol and decreased testosterone with minimal change in LH in sexually inactive and sexually active female- and male-oriented rams thus not providing a method to differentiate between ram classes. |
