Diagnosis and management of spermiostasis in a Shetland stallion

Spermiostasis (or sperm accumulation) is an ejaculatory dysfunction of common occurrence in referral reproductive practice with stallions. The accumulation of sperm in the epididymides, ducti deferens, and ampullae results in ejaculates with a high concentration of degenerated sperm. It is estimated that 5% of light-breed stallions present this condition; however, the incidence is unknown in ponies as this condition has not been reported in these breeds. The present report describes the diagnosis and management of spermiostasis in a 16-year-old Shetland stallion presented for semen collection, evaluation, and cooling test. Semen collection resulted in 73 billion total sperm with necrozoospermia and 67% detached heads. Ten serial semen collections gradually improved sperm motility and morphology. There was no evidence of ampullary plugs in the semen filter throughout the collections. An additional semen collection was procured 48 h after collection 10 for a cooling test. Sodium caseinate cholesterol-loaded cyclodextrin extender resulted in superior sperm motility compared to the native phosphocaseinate extender up to 48 h post-cooling in two semen containers. Sixty days after the initial visit, the stallion returned for a semen freezing test. The ejaculate was normozoospermic, and the owner reported that the stallion had satisfactory fertility for live cover after discharge from the hospital. The thermal longevity test of the frozen-thawed resulted in excellent motility after 120 min of storage at 37°C. In conclusion, herein, we described, apparently for the first time, the occurrence of spermiostasis in a pony stallion. We foresee that other practitioners managing similar clinical cases could have comparable outcomes.