Hormone Concentrations and Semen Parameters in Criollo Breed Stallions Under Training.
Authors: Rossetto Liliana, Farcey María F, Bilbao María G, Bartolomé Julián A, Gallelli María F, Miragaya Marcelo H
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Training Stress and Reproductive Function in Criollo Stallions Training regimens and competition participation raise circulating cortisol in working stallions, yet the consequences for semen quality remain poorly characterised in breeding populations. Researchers compared reproductive parameters between nine Criollo stallions undertaking daily exercise and competition against nine sedentary controls, collecting paired semen and blood samples fortnightly over the spring breeding season and analysing sperm motility, morphology, concentration and chromatin integrity alongside hormone profiles. Whilst testosterone and oestradiol remained unaffected by training (P = 0.28 and 0.97), the exercised group showed significantly elevated cortisol (P = 0.004) alongside measurable deterioration in gel-free seminal volume, progressive sperm motility, total sperm numbers, morphological normality and the combined count of viable, morphologically sound cells (all P < 0.001)—though crucially, all values remained within established equine reference ranges. For practitioners managing breeding stallions in active training or competition, these findings suggest that whilst acute physiological stress suppresses several markers of seminal quality, it does not necessarily compromise fertility; nevertheless, strategically scheduling semen collection, breeding demands and training intensity may optimise reproductive output in performance animals.
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Practical Takeaways
- •Training and competition stress elevates cortisol levels in stallions and reduces semen quality; breeding programs should account for reduced fertility during active training periods
- •Although exercise negatively impacts semen parameters, values remain within clinically normal ranges, suggesting stallions can maintain reproductive function despite training stress
- •Consider timing of breeding soundness examinations or breeding season relative to training intensity when managing Criollo stallion reproductive programs
Key Findings
- •Exercise training significantly increased cortisol concentration in Criollo stallions (P = 0.004) compared to control group
- •Training negatively affected multiple semen parameters including motility (P < 0.0001), normal morphology (P < 0.0001), and total morphologically normal motile sperm (P < 0.001)
- •Despite negative effects of exercise on semen quality, all semen parameters remained within normal ranges established for equine species
- •Testosterone and estradiol concentrations were not significantly affected by exercise training (P = 0.28 and P = 0.97 respectively)