Spermatozoal acrosome dysfunction and its role in stallion subfertility

Area of Science:

• Reproductive biology
• Animal science
• Veterinary medicine

Background:

• Acrosome dysfunction has been a recognized cause of stallion subfertility since the 1990s.
• A severe form, Impaired Acrosomal Exocytosis (IAE), affects stallions with normal sperm parameters, notably in the Thoroughbred registry.
• IAE is linked to a specific susceptibility genotype (A/A-A/A) in the FKBP6 gene, exon 5.

Purpose of the Study:

• To review the role of acrosome dysfunction in stallion subfertility.
• To discuss methods for assessing acrosome function.
• To describe clinical findings of IAE in Thoroughbred and non-Thoroughbred stallions.

Main Methods:

• Review of existing literature on stallion subfertility and acrosome function.
• Clinical case observations of subfertile stallions.
• Genetic analysis for FKBP6 genotype.

Main Results:

• Stallions with normal sperm quality can exhibit severe subfertility due to IAE, often associated with the A/A-A/A genotype.
• Subfertile stallions from other breeds have been identified with reduced acrosomal exocytosis (AE) capacity, independent of the specific Thoroughbred genotype.
• Methods to estimate acrosome function are crucial for diagnosis.

Conclusions:

• Acrosome dysfunction, including IAE, is a significant cause of subfertility in stallions across different breeds.
• Genetic predisposition plays a role, but other factors may also contribute to impaired acrosomal exocytosis.
• Accurate assessment of acrosome function is vital for diagnosing and managing stallion subfertility.