Effect of blocking vision and olfaction on sexual responses of haltered or loose stallions
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Ten stallions were used in a modified split-plot design involving four treatments and two handling methods. Treatments were: a) vision and olfaction not blocked; b) vision blocked, olfaction not blocked; c) vision not blocked, olfaction blocked; and d) vision and olfaction blocked. The methods of handling were: a) stallions turned loose in teasing area, and b) stallions handled on a lead shank. Stallions teased four estrous mares, four diestrous mares and four geldings. Criteria for evaluation of stallion behavior was duration of investigation (sec), of area as well as various portions of the stimulus animal's anatomy, and other pre-copulatory sexual behaviors (Table 1) in duration and frequency. Except for area investigation and no investigation, there were more frequent or longer responses when vision was not blocked compared to blocked (P<0.05). Events associated with display of flehmen and mounting activity were lower (P<0.05) when vision was blocked. Handling a stallion on a lead shank, while teasing, resulted in 23 longer or more frequent pre-copulatory sexual behaviors than when the stallions were loose. There were more frequent or longer (P< 0.05) behavioral responses when stallions were handled on a lead shank and olfaction was not blocked. Events such as duration and number of flehmen responses were lower (P<0.05), and time of no investigation was longer (P < 0.001) when olfaction was blocked. There was no difference (P > 0.05) in the time spent investigating estrous mares, diestrous mares or geldings, except for number of flehmen responses. Number of flehmen responses to estrous mares was higher (P < 0.05) than to diestrous mares, while number of flehmen responses to diestrous mares was higher (P < 0.001) than to geldings. Blocking olfaction did not decrease frequency or duration of sexual behaviors as much as blocking vision (P < 0.05), resulted in decreased (P < 0.05) flehmen responses. Blocking vision significantly decreased (P < 0.05) teasing behaviors, duration of erection, flehmen, and number of mounts regardless of stimulus animal. Stallions utilized visual stimuli to a greater extent than olfactory stimuli. Handling stallions on a lead shank appeared to enhance expression of precopulatory behavior compared to when the stallions were loose.