Improvement of cryopreservation protocol in both purebred horses including Spanish horses

Abstract

There is a widely held belief that the semen of Purebred Spanish Horses (PRE) is of generally poorer quality than that of other breeds, and survives cryopreservation less well. To determine whether this is the case, sperm concentration, viability and morphological abnormalities were examined in a total 610 fresh ejaculates from 64 healthy PRE (N=47) and non-PRE stallions (N=17). Sperm concentration and viability were then re-examined after pre-freezing centrifugation, and once again after freezing-thawing. No differences were observed between the PRE and non-PRE stallions in terms of any sperm quality variable at any observation point. When considering all PRE and non-PRE samples together, differences in sperm viability were observed between fresh and fresh-centrifuged sperm viability (70.1±12.5% compared to 76.3±10.9%; p<0.01). After centrifugation the samples were also more homogeneous in terms of the total number of recovered sperm cells. Centrifugation also improved frozen-thawed sperm viability, reducing differences in sperm quality between individual stallions. For all centrifugations, a sperm:extender ratio of 1:5 was used. This would appear to provide better final results than those reported in the literature for the 1:1 ratio commonly used for PRE stallion sperm cryopreservation. In conclusion, obtained results show that the quality and frozen/thawed results of PRE stallion sperm are not lower than that of non-PRE breeds. In addition, using a 1:5 sperm:extender dilution ratio when selecting sperms by centrifugation prior to freezing, seems to provide better results than those usually reported when using a 1:1 ratio.