Application: There is an unmet need to maximize fertility in stallions through dietary intervention to improve genetic diversity and survivability of rare breeds. Further, there is potential to improve the commercial value of the individual stallion and advance success in sport horses. Welfare and environmental benefits may also be seen, through reducing the requirement for global stallion shipment.
Introduction: Recent advances in fertility, particularly in Artificial Insemination (A.I.), have improved success rates in equine breeding. However, sub-fertile stallions, both through semen quality and fertility limiting behaviour, limit their genetic and commercial success.
Research has shown that dietary supplementation can improve fertility, with evidence for a range of nutrients including l-carnitine, selenium, vitamin E, zinc and docosaheaenoic acid (Stradaioli et al 2004, Brinsko et al 2005, Contri et al 2011). The objective of the field study was to assess the efficacy of a novel complementary feed including these nutrients in an adaptogenic herbal blend for improving semen characteristics in fresh, chilled and thawed semen and promoting stallion behaviour. Improving post-thaw semen motility, particularly, has positive implications for new technologies, such as sexed semen.
Material and Methods: Eight stallions were recruited using sub-fertility as criteria. Sub-fertility was defined as poor libido, advanced age or poor semen characteristics including morphology, motility and concentration, in fresh, chilled and frozen semen. Mean age was 13yrs (5-25yrs), and breeds included Warmblood (5), Thoroughbred (2) and Gypsy Cob (1). Results were scored by the stud manager via questionnaire. The complementary feed was fed throughout one breeding season, and compared against the previous year. Stallions had previously either been on no supplement, or a simple Vitamin E and Selenium only supplement, which was discontinued prior to trial.
Results: Semen characteristics showed a significant (P<0.05) improvement, with increased concentration, motility and progressively motile sperm cells (PMSC). Individual observations included an extended breeding season with greater consistency throughout (Fig 1). Insufficient data was collected to assess stallion behaviour. Additional vigour, stamina and sexual interest were reported in observations of stallions that had previously exhibited fertility limiting behaviour.
Fig 1. Comparison of PMSC from ‘Black Pudding’ during 2018 (Vit E only) and 2019 (trial supplement)
Conclusion: Questionnaire results and observations from stallion managers showed a potential benefit of supplementing breeding stallions with the complementary feed. In particular, improvements in post-thaw motility provides an opportunity for diet to support technological advances in equine reproduction, improving the stallion’s value whilst improving welfare with a reduced requirement for multiple coverings or global stallion travel. Research is ongoing to extend quantitative data analysis in the future.
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