Spermiostasis in stallions: a retrospective study of clinical cases

Abstract

Spermiostasis refers to the abnormal accumulation of spermatozoa in the epididymides and ductus deferens. Affected stallions, commonly called ‘sperm accumulators’, may exhibit high concentrations and total numbers of sperm in their ejaculate, low sperm motility and a high proportion of sperm with head-tail separation (i.e. detached heads). Anecdotal accounts of the clinical syndrome have been described. However, there are few published reports of semen parameters from affected stallions. The goal of this study was to compare semen analysis data for stallions with spermiostasis versus clinically normal stallions. Semen parameters from 10 stallions with spermiostasis and 10 normal stallions were analyzed. Criteria for inclusion as an affected stallion included a high sperm concentration, high total number of sperm in the ejaculate and low total sperm motility in the initial collection which improved with subsequent collections. Client stallions were collected as needed until sperm concentration and motility normalized. The normal stallions were collected once daily for 8 consecutive days for comparison. Data were analyzed by one way analysis of variance with post-hoc Student’s t-test (SAS). The average ages of normal and affected stallions were 10.0 0.9 and 13.0 2.4 years (mean sem), respectively (p<0.05).