Abstract
Simple SummaryGoat semen was previously considered to be problematic to freeze because of reactions between the semen and the components of the freezing media that were available at the time. However, there have been reports of several successful attempts to freeze goat semen in recent decades using various protocols, resulting in usable post-thaw sperm samples. In the present study, we adapted some of these methods to suit the particular conditions under which we had to work. We were able to produce thawed samples with acceptable sperm quality which were sent to a sperm bank for long-term storage.Although several protocols for cryopreserving buck semen are described in the literature, they differ widely in factors such as season and method of semen collection, extender and sperm concentration. Therefore, choosing a protocol that is suitable for a particular on-farm situation can be problematic. In the present study, semen was collected by artificial vagina from seven bucks on a farm located approximately 90 minutes’ drive away from the laboratory, about 6 weeks before the start of the goat breeding season. The semen was immediately extended in warm semen extender containing soy lecithin and was placed in an insulated box with a cold pack for up to 4 h, during semen collection from the remaining bucks and subsequent transport to the laboratory. Following centrifugation at 4 °C and resuspension in the soy lecithin extender to a sperm concentration of 800 × 106 spermatozoa/mL, 0.25 mL plastic straws were filled and frozen in racks 4 cm above the surface of liquid nitrogen. This simple protocol resulted in an acceptable post-thaw quality for all seven bucks, with a mean post-thaw motility of 55 ± 21% and mean fragmented chromatin of 3.27 ± 1.39%. Normal sperm morphology was >90% in all ejaculates. The semen was sent to a gamete bank for long-term storage.
Highlights
There are relatively few papers on freezing goat semen compared to the considerable volume of literature available for species such as the bull, but the reports that are available for buck semen present a bewildering array of protocols
Seven Landrace bucks were transported to a goat farm in Sweden that was certified to be free of caprine arthritis/encephalitis virus (CAEV), where they were held in isolation for 6 weeks prior to semen collection according to the regulations laid down by the Swedish
Teasers were brought into estrus, two ejaculates were collected from each buck, a non-egg yolk containing extender was added, the semen was transported, cooled, and the seminal plasma was removed by centrifugation before resuspension to the final concentration for freezing in liquid nitrogen vapor
Summary
There are relatively few papers on freezing goat semen compared to the considerable volume of literature available for species such as the bull, but the reports that are available for buck semen present a bewildering array of protocols. Some examples are given in (2 h, 4 h), what the final sperm concentration should be (ranging from 50 × 106 /mL to 1000 × 106 /mL), pellet or straw, size of straw (0.25 mL or 0.5 mL), and the method of freezing (dry ice for pellets, vapor freezing or controlled rate freezing for straws) All of these factors could influence post-thaw sperm quality. The range in sperm concentration among the various studies may reflect the intended use of the semen: artificial insemination (AI), in vitro fertilization (IVF), laparoscopic insemination, etc., but could have an effect on the ability of the spermatozoa to survive freezing These different studies reflect the wide variety of conditions under which buck semen might conceivably be collected for freezing, but each of the factors involved could have an effect on sperm cryo-survival.
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