State-of-the-art of boar sperm preservation in liquid and frozen state

Abstract

Pig breeding is mainly conducted through Artificial Insemination (AI) in Western and developing countries. Apart from requiring specific catheters and trained staff, preserving boar semen in proper conditions is needed to ensure high reproductive performances. Although, at present, boar sperm may be preserved in liquid (15-17ºC) or frozen states, more than 95% of AIs are conducted using liquid semen. The present work reviews the state-the-art of these two preservation technologies. Thus, the composition and types of extenders for liquid-stored semen are discussed, together with the specific requirements for boar sperm, which are stored at 15-17ºC. Commercial extenders for liquid semen are compared and the effects of storage on sperm quality are also summarised. In the second part of the manuscript, the main features of boar sperm cryopreservation are described and reference to cryodamage is also made. These cryoinjuries mainly affect sperm motility, membrane permeability and chromatin integrity. Furthermore, the individual variability in the sperm resilience to withstand cryopreservation procedures is reviewed and a brief summary about freezability markers is also included. Final sections briefly discuss the improvement of freezing extenders with additives, such as seminal plasma and antioxidants, and highlight the relevance of using a proper AI technique to avoid dramatic drops in reproductive performance.

Preservation of boar semen: An update

“…A boar semen sample can become contaminated as a result of the infection of the male reproductive tract or during the collection and processing of the semen to obtain seminal doses (Bryła & Trzcińska, ; Kuster & Althouse, ); factors like glucose and storage temperature at 15–18°C also promote bacterial proliferation (Yeste, ). Maroto Martín et al () determined that 75% of the analysed samples were contaminated with at least one type of bacterium, with Escherichia coli being the most common; another study showed that Chlamydia suis remains viable and infectious, being capable of spermicidal activity after 7 days of storage at 17°C (Hamonic, Pasternak, Käser, Meurens, & Wilson, ).…”

“…Adequate temperature management during semen processing is central to the quality of the stored samples, since mammalian sperm, especially boar sperm, are sensitive to a rapid reduction in temperature due to the physicochemical characteristics of the membranes (Parks & Lynch, ), altering the lipid phase transition and the phase separation processes (Schulze, Henning, Rüdiger, Wallner, & Waberski, ), which occur at 18–24°C (Canvin & Buhr, ), reducing the lateral movements of the membrane phospholipids and causing irreversible changes in the membrane proteins (Canvin & Buhr, ; Yeste, ). There is a greater membrane protein/phospholipid ratio (1.26) and a smaller proportion of cholesterol (0.26) in boar sperm that lowers the tolerance to the effect on the temperature changes compared to other species like human and bull (Parks & Lynch, ).…”

“…Immediately after ejaculation, the semen pH is approximately 7.4 ± 0.2 (Gadea, 2003). Its descent causes a reduction in the sperm energy metabolism and motility (Yeste, 2017), which indicates the need to include buffers to the extender to control variations in the pH; in addition, the external pH could affect the flagellum movement of the sperm (Gatti, Chevrier, Paquignon, & Dacheux, 1993). Lactic acid is the main metabolite produced by the oxidation of glucose and fructose and can be used as a parameter to evaluate the quality of boar semen (Rigau, Piedrafita, Reverter, Canal, & Rodríguez-Gil, 1996).…”

Reproductive performance of sows inseminated with semen doses stored for up to seven days in long-term extender in a field condition

“…In swine production, artificial insemination (AI) is used with liquid-stored semen. Extenders are used to increase the volume of the ejaculate, provide energy to sperm, protect against cold shock, maintain a stable pH, ensure an adequate osmotic pressure, and prevent bacterial growth during storage (Yeste, 2017). The extenders are divided into two main groups according to the capability of promoting the viability of sperm cells over time: short-term (up to three days) and long-term (more than four days) (Yeste, 2017).…”

Assessment of Ageing-Dependent Effects on Sperm Functions following Semen Cryopreservation

“…1,2 Cryo-induced damage to spermatozoa is attributed to membrane deterioration caused mainly by the formation of intracellular ice and increased oxidative stress, resulting in a loss of the sperm fertilizing ability. 3 It is noteworthy that ageing-dependent processes in frozen-thawed semen occur in different sperm compartments, and are associated with membrane modifications of specific lipid-protein interactions, activation of an apoptosis-like mechanism and reduced genomic integrity, which consequently compromise sperm cryo-survival.…”