Enhancing stallion sperm functionality and fertility: techniques in isolation, preservation, and prediction

Aims and Overview In the equine breeding industry, the challenge of sub-fertile stallions within breeding programs prompts the need for advanced sperm technologies to improve reproductive outcomes. The broad aim of this thesis targets the three key stages in stallion sperm processing prior to insemination: sperm processing and isolation, quality diagnosis, and in vitro sperm storage. 1.Sperm processing and isolation: Current semen extension processes involve adding commercial extenders and may lack crucial steps like removal of seminal plasma, which can impact in vitro storage quality. Faster and simpler methods for isolating high-quality spermatozoa, without the need for specialized equipment, have potential to be widely adopted and enhance the outcomes of artificial insemination. 2. Quality diagnosis: Traditional evaluation of sperm function considers factors like ejaculation volume, sperm concentration, morphology, and motility. However, these parameters mainly detect severe impairments, not relative degrees of infertility. A unique correlation between oxidative stress markers and fertility in stallion spermatozoa opens the possibility of a diagnostic test to measure mitochondrial function, potentially providing a more nuanced assessment of ejaculate quality. 3. In vitro sperm storage: Equine sperm storage methods are vital due to unpredictable ovulation timing in mares. While chilling and cryopreservation are common methods, they pose challenges for certain spermatozoa from problem stallions. Further understanding of biochemical and structural changes during storage can advance the field of in vitro ambient temperature sperm storage in stallions. By addressing these key stages, this thesis aims to contribute to the improvement of stallion reproductive health and the overall success of equine breeding programs.