Post-Thaw Quality of Spermatozoa Frozen with Three Different Extenders in the Murciano Granadina Goat Breed

SIMPLE SUMMARY: In caprine species, the semen quality of thawed samples still needs to be improved in order for this type of semen to provide an acceptable pregnancy rate when it is used for artificial insemination. It is therefore essential to have an adequate freezing protocol and extender for this species. By adapting freezing protocols that have proven successful in other species, such as pigs, together with the development of an extender that protects the sperm cells from damage caused by the freezing and thawing processes, and taking into account its composition in nutrients and cell-membrane-stabilizing substances, it has been possible, at least in vitro, to achieve high sperm quality in buck semen. In vivo studies of the fertilizing capacity of the semen cryopreserved in this way will be the next step to verify the effectiveness of the extender and semen-freezing protocol described in this work. ABSTRACT: Artificial insemination (AI) with frozen semen in goats still presents serious difficulties, especially in certain goat breeds, in spite of technological progress. The aim of this work is the in vitro study of seminal extenders adapted from those used on other species to evaluate the response of goat sperm to several homeostatic conditions in order to achieve optimal post-thaw semen quality. Three different extenders based on different activity principles were used: (1) extender according to the methodology proposed for pigs, (2) skimmed-milk-based extender according to the methodology proposed for goats in France, and (3) a new egg-yolk-based extender replacing membrane-protective surfactants with sodium dodecyl sulfate (SDS) and named by our team as extender “IMIDA”. The freezing guidelines were those proposed for the freezing of porcine semen. The results obtained show that the egg-yolk-based extenders have good parameters of sperm motility at thawing, studied objectively using the computer-assisted sperm analysis (CASA) system and also subjectively. In particular, in the sperm resistance test after five hours, the thawed sperm containing SDS in their composition showed an optimal average on every evaluated parameter. The new IMIDA extender provided the highest sperm quality averages, so it could be a good extender to use in cryopreservation of semen in the caprine species.