Hormonal and behavioral correlates of emotional states in sexually trainedboars

Physiological and behavioral traits of sexually mature boars were compared between episodes of copulation and sexual frustration in order to determine reliable indicators of the differences in emotional states. Ten boars, app roximately 6 mo of age, were trained to mount a stationary artificial sow ( ArtSow) and to ejaculate when digital pressure was applied to the extended penis. This method of semen collection is the typical procedure of the indu stry. All 10 boars used in this study were fully trained to this procedure before the onset of the study. Each boar was subjected to trials in which o ne of the following two treatments was applied. In the control (CTRL) treat ment, boars were treated the same as during their training (i.e., allowed t o complete ejaculation). In the frustration (FRUS) treatment, boars were al lowed to mount the ArtSow, but because no manual pressure was applied to th e extended penis, ejaculation never occurred. Blood was collected via indwe lling catheters before onset of the trial, during exposure to the ArtSow, a nd after returning to their home pen. Concentrations of testosterone, corti sol, and beta-endorphin were quantified. Behavior of the boars was recorded during exposure to the ArtSow and for 30 min after return to their home pe n. Relative to preexposure levels, serum cortisol increased (P < .05) durin g CTRL exposure and after exposure to both treatments (CTRL; P < .04 and FR US; P < .06). Serum testosterone did not change during and after either tre atment. Serum concentrations of beta-endorphin did not change during or aft er CTRL trials, but serum beta-endorphin was greater (P < .05) during FRUS than during CTRL trials. Behavioral analysis revealed that boars spent less time lying down and more time moving about their home pen (P < .05) after a FRUS than after a CTRL trial. In summary, serum cortisol did not allow us to distinguish between the excitement of copulation and the negative affec t associated with sexual frustration, whereas increases in serum beta-endor phin and motor activity seemed to be indicators of the negative emotional s tate of sexual frustration in trained boars.