Testosterone and progesterone in peripheral plasma during the oestrous cycle of the mare.

The research aims to understand the changes in the levels of testosterone and progesterone hormones in a mare during its oestrous cycle. The study shows that the testosterone levels peaked during the oestrus phase for most of the mares studied, and a smaller peak also occurred about two weeks before the next oestrus.

Understanding the Oestrous Cycle

• The oestrous cycle in mares refers to the period where the female horse undergoes reproductive cycle. This cycle plays an important role in the mare’s fertility and ability to reproduce. The cycle includes four phases, mainly the proestrus, oestrus, metestrus, and diestrus.
• During the oestrus phase, females are receptive to mating and their bodies prepare for potential fertilization of an egg. This research primarily focuses on the hormone levels during this phase.

Observing Hormone Levels

• The hormones being observed are testosterone and progesterone. These hormones are important for sexual characteristics, and reproduction.
• Testosterone, although typically associated with males, is also produced in females. In the context of this study, the researchers link testosterone levels to the horse’s fertility phase, noting that levels ranged from 15 to 70 pg/ml and were higher at oestrus.
• Progesterone is a hormone that prepares the uterus for pregnancy and maintains pregnancy once conception has occurred. Its levels usually rise and fall throughout the oestrous cycle.

Key Findings

• The researchers noted testosterone levels were higher at oestrus in 4 of the 6 mares studied, indicating a clear pattern of higher testosterone levels during the most fertile part of the oestrous cycle.
• The study also found that another testosterone peak occurred 11-13 days before the next oestrus in these 4 mares. This indicates that there may be a secondary peak in testosterone levels in anticipation of the next oestrus.
• Interestingly, this second testosterone peak either occurred before or after a fall in progesterone levels in 3 mares, suggesting there may be a correlation between these two hormone levels in a mare’s oestrous cycle.

Implications of the Study

• This research adds valuable knowledge to understanding the relationship between hormone levels and the oestrous cycle in mares. This could potentially aid in predicting the best times for breeding and could improve the success rate of conception.
• The observation that a secondary peak of testosterone occurs around two weeks before the next oestrus may serve as a helpful indicator for estimating the timing of the next fertility phase.
• The potential link between testosterone and progesterone levels offers an interesting avenue for further research around hormonal patterns in the oestrous cycle.