Advances in sperm cryopreservation of samples collected by vaginal artificial and electroejaculation from Blanca-Celtiberica goat breed

Abstract

Blanca-Celtibérica goat is an endangered autochthonous breed from Spain. To prevent the disappearance of these autochthonous breeds and in order to maintain the genetic diversity, the Food and Agriculture Organization of the United Nations (FAO) recommends the preservation of these breeds by in situ and ex situ conservation programs (FAO, 2010). The creation of Genetic Resource Banks (GRB) is a measure of ex situ conservation and allows us the storage of semen, oocytes and embryos indefinitely, being an essential tool in order to preserve the genetic diversity of species. The most widespread application in the development of GRB has been the semen collection and its freezing. This requires the knowledge of reproductive physiology as well as the suitable assisted reproductive technologies for each species. In the case of the Blanca-Celtibérica goat breed, the geographical location in addition to extensive production systems and the lack of buck center make semen collection by routine techniques not feasible. Thus, when animals can not be trained to semen collection by artificial vagina, there are other alternatives such as the electroejaculation, being possible to obtain semen of males living in the countryside. Besides the semen collection, the conservation of semen samples is also a key aspect. Up to date, although several studies have been carried out on sperm cryopreservation in caprine, most of them have used samples collected by artificial vagina. However, it is known that the semen collection method influences on the sperm production and composition of seminal plasma (Marco-Jiménez et al., 2005; Marco-Jiménez et al., 2008) as well as the cryoresistance of sperm samples (Álvarez et al., 2012). Another problem during the buck semen cryopreservation is the low seminal quality found after thawing when freezing extenders based on egg yolk or skim milk are used. Some components of egg yolk and skim milk have negative interactions with seminal plasma as a result of the production of toxic compounds to the spermatozoa. This effect could be more pronounced on sperm samples collected by electroejaculation since the volume of seminal plasma is higher than in samples obtained by artificial vagina. With this background, the general aim of this Doctoral Thesis has been to develop an optimal method in order to collect and cryopreserve buck semen of Blanca-Celtibérica breed which allow us to storage seminal doses to create a Germoplasm Bank.