Effect of the type of egg yolk, removal of seminal plasma and donor age on buck sperm cryopreservation

Abstract

This study was designed to assess the effect of different types of egg yolk used in buck sperm cryopreservation and its concentration depending on the presence or absence of seminal plasma on sperm freezability from males of one and two years old. The aim was to reduce the potential risk of microbiological contamination of the extenders by replacement of fresh by pasteurized powdered egg yolk, and also to study the effect of the clarified fresh egg yolk, obtained by centrifugation of fresh egg yolk twice at 10.000×g for 45min at 4°C. Briefly, fresh ejaculates (n=6) from six to eight bucks were collected by artificial vagina in two consecutive autumns. After collection, ejaculates were mixed and split into two samples. One sample was washed twice by centrifugation at 600×g for 10min. Then, the pellet was split into three equal aliquots and re-suspended in an extender containing 15% (v/v) of different type of egg yolk (powdered, fresh or fresh clarified) supplemented with 5% glycerol (v/v) in Tris-based medium. The other semen sample was directly split into three equal aliquots and re-suspended in the same extenders, but containing only 2% (v/v) of different type of egg yolk (powdered, fresh or clarified). All samples were chilled for 4h at 5°C and then frozen to −196°C. The results indicated that there was not superiority on the protective capacity of the different egg yolk types, either at 15 or 2% concentration on respective samples in post-thaw sperm analysis, regardless of donor age. Analyzed sperm parameters also showed better results in the washed samples than in the non-washed samples irrespective of the type of extender used and donor age. The use of clarified egg yolk did not offer any benefit to the fresh egg yolk, thus complicating the preparation process of such preservation media. Therefore, washing procedure of buck spermatozoa and the use of powdered egg yolk as a replacement for fresh egg yolk may be recommended for cryopreserving buck spermatozoa due to its efficiency and safety measures.