Effect of sexual arousal on gonadotrophin-releasing hormone, luteinizing hormone and follicle-stimulating hormone secretion in the stallion.

This study explores the impact of sexual arousal on the secretion of reproductive hormones (GnRH, FSH and LH) in stallions. It reveals that when stallions encounter an oestrous mare, there is a rapid increase in the pulses of these hormones.

Methodology

• The research study involved five stallions which were used as subjects for the experiment.
• It was conducted late in the physiological breeding season to ensure the stallions’ hormones were naturally at high levels.
• The stallions were fitted with indwelling pituitary venous cannulae. This equipment allowed for the smooth collection of blood from the hypothalamo-hypophyseal portal vessels and the pituitary, without causing distress to the stallions.
• The team collected blood samples from the stallions at intervals of five minutes for several hours while they were resting.

Initial Observations

• Before the introduction of the oestrous mare, the stallions showed pulses of gonadotrophin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) approximately once an hour.
• This stable baseline was necessary to identify any changes in hormone levels due to the introduction of the mare.

Experiment with an Oestrous Mare

• After the initial observation period, the researchers introduced an oestrous mare (a mare in heat) to each stallion individually for a duration varying between 8 to 30 minutes.
• This exposure to the mare was meant to stimulate sexual arousal in the stallions.

Outcomes

• The interaction with the oestrous mare led to rapid pulses of GnRH, FSH, and LH secretion in all stallions.
• The increase in hormone secretions highlights the influence of sexual arousal on the hormones along the reproductive axis.

Conclusion

• The research suggests that sexual arousal in stallions significantly impacts reproductive hormone secretion.
• This finding could be important for understanding and manipulating breeding behaviors and fertilization timing in horse breeding initiatives.