Rationale: Artificial insemination allows sport horse stallions within breeding programmes to breed and compete concurrently. The level of exercise of stallions complete during the breeding season is a controversial subject. Daily exercise at low intensities is important for the mental and reproductive well-being of the stallion, however higher intensities of exercise, as seen in competing stallions, may have detrimental effects on seminal quality. The purpose of this study was to gain a greater understanding into the effects of competition and discipline on equid stallion semen through analysis of seminal parameters. The identification of optimal competition management for breeding stallions may lead to increased stallion fertility and economic gain. Methods:This retrospective study evaluated the seminal data of 1130 stallion collections from two UK based stud farms between 2009 and 2015. Seminal volume, concentration and progressive motility were analysed for differences between competing and non-competing stallions, then for differences between stallion disciplines. Results:Competing stallion semen concentration and progressive motility was significantly lower than noncompeting stallions (p<0.05). Semen volume was significantly higher in competing stallions (p<0.05) than noncompeting stallions. Non-competing stallion semen count was significantly higher than that of competing stallions (p<0.05). Conclusion:The difference in semen quality between competing and non-competing stallions, as well as the difference between disciplines suggests endocrinological and physiological changes occur in relation to training intensity and competition. Further research into semen quality considering exercise and competition will allow for contextualisation as to why these differences occurred.

This publication is a compilation of all Research Abstracts presented at the Ninth International Conference on Equine Exercise Physiology. Unlike previous ICEEP conferences there will not be a conference proceedings of full length manuscripts. These abstracts succinctly summarise a wide array of investigations relevant to the equine athlete, and will be useful to veterinarians and others involved in management of horses used for sport, work and competition. The abstracts encompass the topics of Applied PhysiologyIntroduction: The ability to accurately assess equine oxygen consumption (VO2) under field conditions has been limited by the need for unrestricted gas exchange.Methods: Two variations of a mask and an associated electronics control module (ECM) were designed to enable breath-by-breath measurement of airflows with two 8.0 cm diameter pneumotachometers located 7.5 cm in front of each narus and connected to differential pressure transducers mounted on the outside of the mask. The ECM was comprised of electronics for signal filtering to the flow transducers, an oxygen sensing cell, and an analog-to-digital converter all powered by a lithium-ion battery. The battery also powered a pump connected to gas sampling ports between the nares and pneumotachometers. Airflow and oxygen content of inspired and expired gases were recorded through the ECM and electronically transferred to a notebook. VO2 was determined from these recordings by an operator using a customized software analysis program. One mask encased the lower head (E). The other left the jaw free so horse could wear a bit and be ridden (R). Multiple treadmill exercise tests were undertaken by 6 horses to measure VO2max and blood gases. Each mask was worn twice and results compared to those from an open flow-through system (O) by 2-way RMANOVA (P<0.05). Utility of the system was evaluated using the intraclass correlation coefficient of 4 independent raters.Results: Blood gases and VO2max (152.0 ± 4.0 (mean ± SEM; O), 147.7 ± 4.3 (E), 150.7 ± 3.3 (R) ml/(kg.min) were not different between masks. VO2 measures were reproducible for each mask. Agreement between the 4 raters was excellent (intraclass correlation coefficient = 0.99).Conclusions: Masks capable of measuring VO2 during field exercise were developed, tested and found accurate by multiple users.Ethical Animal Research: Studies performed were approved by the Institution's Animal Care and Use Committee (protocol #3807). Sources of funding: Institutional sources. Competing interests: Washington State University has filed notice of its intent to apply for a patent for facemask used in this study.Introduction: Exertional myopathies are a common cause of exercise intolerance in the equine athlete, and Polysaccharide Storage Myopathy (PSSM) is a widely described muscular disease. It is characterized by an accumulation of abnormal glycogen in myofibers due to a genetic defect in the skeletal muscle glycogen synthase (GYS1) enzyme. We hypothesized that energy production through oxidative phosphorylation (OXP...