Body Condition, Metabolic Parameters and Semen Traits in Purebred Spanish Horses.

Overview

• This study investigates how body condition, specifically obesity, affects the metabolic health and semen quality of Purebred Spanish stallions.
• The research finds that obese stallions exhibit metabolic changes linked to poorer semen traits, especially lower sperm count and motility.

Introduction and Context

• The Purebred Spanish horse is an important breed with growing interest in preserving elite genetics.
• Assisted reproductive technologies rely on good reproductive performance, which is affected by the stallion’s systemic health.
• Body condition score (BCS) is used to classify overall fatness and health; this study focuses on how BCS relates to metabolic and reproductive parameters.

Research Objectives

• To assess how different body conditions in stallions (normal vs. obese) affect metabolic and endocrine markers in blood.
• To evaluate changes in semen quality parameters influenced by body condition and related metabolic changes.
• To analyze relationships between metabolic health indicators and semen characteristics using statistical methods like ANOVA and PCA.

Methodology

• Sample: 26 Purebred Spanish stallions were studied during February to May in 2024-2025.
• Body Condition Scoring: Using the Henneke scale, stallions were split into:
  • Low BCS group (4-6): considered normal condition (n=14)
  • High BCS group (7-8): considered obese (n=12)
• Data Collection:
  • Blood samples for metabolic and endocrine parameters like insulin, triglycerides, glucose, and cholesterol.
  • Semen samples for evaluation of sperm count, total sperm motility, and other quality variables.
• Data Analysis:
  • ANOVA used to compare groups on metabolic and semen parameters.
  • Principal Component Analysis (PCA) performed on blood and semen parameters to identify patterns and correlations.
  • Correlation analysis to examine associations between BCS and metabolic markers.

Key Findings

• Metabolic and Endocrine Changes:
  • Obese stallions (high BCS) had significantly higher insulin and triglyceride concentrations compared to normal condition stallions.
  • Positive correlations were found between BCS and insulin (r = 0.576) and between BCS and triglycerides (r = 0.525), indicating higher body fat relates to metabolic dysfunction.
• Semen Quality:
  • Stallions with high BCS showed a significantly lower total sperm count (p < 0.0001).
  • Total sperm motility was also reduced significantly (p = 0.0055) in obese stallions.
  • These differences indicate poorer semen quality associated with obesity.
• Principal Component Analysis (PCA):
  • Blood PCA identified a primary component (PC1) linking glucose, insulin, triglycerides, and cholesterol, highlighting a metabolic syndrome-like profile in obese stallions.
  • Semen PCA showed PC1 linked with general semen quality and PC2 linked with total sperm count.
  • Although no direct correlation was observed between PCA components and BCS alone, combining blood and semen PCA indicated that elevated insulin, triglycerides, and cholesterol are significantly associated with a reduced total sperm count.

Interpretation and Implications

• The observed decline in semen quality among stallions with high BCS appears driven more by metabolic and endocrine dysfunctions rather than adiposity itself.
• Higher insulin and triglyceride levels suggest insulin resistance and lipid metabolism disturbances, common in obesity-related metabolic syndrome.
• These metabolic changes negatively impact sperm production and motility, which are crucial for fertility.
• The study underscores the importance of monitoring and managing metabolic health in stallions used for breeding to maintain optimal reproductive performance.

Conclusion

• Obesity in Purebred Spanish stallions is associated with metabolic disturbances characterized by increased insulin and triglycerides.
• These metabolic changes correlate with poorer semen traits, particularly reduced sperm count and motility.
• Interventions aimed at metabolic health may improve reproductive outcomes more effectively than focusing on body fat alone.
• This research encourages breeders and veterinarians to integrate metabolic assessments into stallion reproductive management protocols.