Determination of the relationship between sperm morphologic classifications and fertility in stallions: 66 cases (1987-1988).

The research article reviews the correlation between the morphological classification of sperm, which includes their shape and structure, in stallions and their fertility rate. The study found a significant relationship between these two factors, particularly noting that a higher percentage of sperm with severe defects resulted in lower fertility.

Objective and Methodology

• The underlying objective of the study was to observe the connection between sperm morphology, i.e. the structure and formation of sperm cells, and the fertility of stallions over 99 breeding seasons across two years.
• The researchers studied the breeding records of these animals and classified sperm cells from their semen based on their morphology. The classification involved defining normal sperm and those with major defects such as abnormal heads, proximal droplets, and abnormal midpieces.

Results

• The study found a substantial positive correlation (r = 0.34, P less than 0.01) between the percentage of morphologically normal sperm and the estimated per cycle fertility rate in stallions.
• The research also found a significant inverse correlation (r = -0.36, P less than 0.01) between sperm with major defects and the same fertility estimates. This indicates that stallions with a higher percentage of defective sperm had lower fertility rates.

Conclusion

• Multiple variable regression displayed that the variation in two morphological features categorized as major defects, specifically abnormal heads and proximal droplets, accounted for most of the fertility variation.
• The research concluded that a greater percentage of defective sperm, especially those with major defects or a combination of major and minor defects, was associated with a more significant reduction in fertility in stallions.