Semen characteristics in a sub-fertile Arabian stallion with idiopathic teratospermia.

This research discusses the case of a sub-fertile Arabian stallion that has a high number of abnormal sperm, a condition known as teratospermia, despite having no observable health issues or reproductive abnormalities.

Research Background

• The researchers observed a 5-year-old Arabian stallion that was not able to breed successfully; the pregnancy rate achieved with its semen (fresh/extended) was 26.3%, significantly lower than average.
• Teratospermia is a condition that affects fertility in males and is characterized by the presence of sperm with abnormal morphology.

Observations and Results

• The stallion was found to be in good health and no abnormalities were found in its reproductive system.
• Upon examining several of the stallion’s ejaculates, researchers found the sperm production was consistent and within normal ranges. However, they also found that semen quality was extremely poor.
• The majority of the abnormal sperm exhibited defects in the head and mid-piece structures.
• Among these defects included microcephalic (smaller than normal) and/or tapered heads, as well as great variation in the dimension of sperm heads both within a single ejaculate, and among different ejaculates.
• Another peculiar defect observed was a swollen or roughened mid-piece of the sperms, which researchers attribute to the accumulation of cytoplasmic-like material and abnormally formed mitochondrial sheath.
• Other prevalent abnormalities included nuclear vacuoles, issues with the acrosome (a part of the sperm), and the presence of teratoids (abnormally formed cells).

Conclusions

• Despite the various sperm abnormalities found, researchers could not identify any visible causes like health problems or degenerative signs in the testicles that usually bring about teratospermia.
• Given this, along with the stallion’s normal sperm production rates and constant presentation of abnormal sperm, researchers suggest that an inherent (passed down) or congenital (present from birth) issue with spermatogenesis (the process of sperm production) is the probable cause of his sub-fertility.