Sexual arousal intensity modulates copulatory behavior and semen quality in Arabian stallions: Effects of age,...

Stallion sexual behavior during semen collection can be influenced by multiple factors, yet the role of sexual arousal intensity remains underexplored. Understanding how arousal modulates behavioral and physiological reproductive traits is essential for improving artificial insemination (AI) efficiency and semen quality. This study aimed to evaluate the effects of sexual arousal intensity, age, origin, and semen collection method on stallion sexual behavior and the quality of fresh and frozen semen.

Thirteen Arabian stallions (7 Tunisian, 6 foreign parentage) aged 6-20 years (total ejaculates = 49) were assessed during semen collection using either a dummy or an estrous mare. Sexual arousal intensity was scored on a four-point scale (- to +++). Behavioral responses, mounting and erection parameters, and semen traits were recorded. Fresh semen was evaluated for volume, motility, concentration, and morphology; frozen semen was assessed for motility, viability, membrane integrity, and abnormalities. Data were analyzed using multifactorial analysis of variance with significance at p < 0.05.

High arousal (+++) increased vocalizations, anogenital sniffing, and Flehmen responses (p < 0.05) but prolonged preparation time (p = 0.05). Low arousal (-/+) prolonged full erection duration (p < 0.01) and improved sperm motility in fresh and frozen semen (p < 0.01). Stallions of foreign origin exhibited higher fresh semen motility (p < 0.01) but required longer preparation and collection times (p < 0.05). The estrous mare method improved fresh semen motility and concentration (p < 0.05) but did not affect frozen semen traits. Younger stallions produced larger semen volumes, but had higher abnormal sperm counts in fresh samples, whereas older stallions showed more abnormalities post-freezing (p < 0.01).

Sexual arousal intensity significantly modulates both behavioral and semen quality parameters in stallions. Lower arousal is associated with prolonged erection and superior sperm motility, suggesting dissociation between behavioral excitement and physiological semen traits. Collection from an estrous mare can enhance fresh semen motility, though the dummy remains safer for handlers. These findings highlight the importance of tailoring semen collection protocols to individual stallion profiles to optimize AI outcomes.