Endocrine and metabolic profile of peripubertal Standardbred colts.

This study investigates the hormone levels in growing Standardbred colts (young male horses) and their connection with puberty, testicular development, and fat accumulation. The research highlights that the onset of puberty, marked by increased testosterone, aligns with rapid testicular growth but is not linked to an upsurge in other studied hormones or body fat.

Methods of Study

• 23 healthy Standardbred colts were observed over a period of twelve months and blood was sampled every four weeks to measure the concentrations of different hormones.
• The horses’ weight, body fat percentage, and testicular volume were tracked and estimated using ultrasound.
• The advent of puberty was deemed when testosterone levels were found to be two standard deviations above the average of previous measurements.
• Hormones such as FSH, LH, leptin, estradiol-17β, androstenedione, IGF-1, insulin, inhibin-A, and inhibin-B were analysed over a span of seven months around the peripubertal period to gain deeper insights into the hormonal fluctuations during this phase.

Key Findings

• Puberty onset in the studied colts, who were born in spring, was estimated at 13 months of age. This was marked by a significant rise in testosterone.
• The onset of puberty was related to a rapid increase in testicular growth. This growth, however, was not connected with an increase in skin fat or the hormone leptin.
• Post-pubertal period showcased significant escalation in plasma inhibin-B levels, while the levels of inhibin-A, androstenedione, FSH, LH, or estradiol-17β did not demonstrate similar increase.

Conclusion

• The research concluded that in Standardbred colts, the commencement of puberty, denoted by a rise in testosterone, is associated with rapid testicular growth.
• However, it was not linked with an increase in gonadotropins, IGF-1, cutaneous body fat or leptin, suggesting that these factors may not play crucial roles in equine puberty.
• These findings provide a nuanced understanding of the puberty process in horses, and can potentially inform future research and equine health practices.