Choice of extender to optimize boar sperm production
The choice of boar semen extender in the process of artificial insemination in pig production has a significant importance. Some 90% of a typical semen dose consists of semen extender. The semen extender has a couple of important functions. One major function is to increase the volume of the semen to allow the production of several semen doses from one native boar ejaculate.
During the preparation of the semen doses, the native boar ejaculate is divided into many small parts. Each of these parts, which will later become the semen doses, must be extended to a minimum volume e.g., 80 ml for cervical AI and some 50 ml for post-cervical AI. The minimum volume of an AI dose is necessary as the sow’s uterus requires a minimum volume of liquid, so that the sperm cells can be transported via peristaltic movements towards the site of fertilization in the oviducts. The liquid of the semen dose works as carrier liquid for the sperm cells here.
Beside increasing the volume of a semen dose, the semen extender also needs to preserve the functional characteristics of the spermatozoa and must maintain an optimal fertility level. The sperm cells in a semen dose are exposed to many stressors on their way from semen collection, until the process of insemination. The semen extender has to protect the sperm cells against these stressors. Typical stressors include the transport of the semen dose from the boar stud to the sow farm. The transport distance and time can be quite significant and last several days. During this time the semen dose experiences e.g., temperature fluctuation, mechanical stress, and light exposure. Other stress factors for the sperm cells in the semen dose are metabolites and bacteria in the liquid semen and their metabolites as well. The dilution itself causes stress for the individual spermatozoa, as the diluent replaces the native environment of the sperm cells with semen extender.
Modern and especially long-term semen extenders, include several components to preserve the sperm function against the stressors. First, a pH-buffer is needed to stabilize the pH-value during storage. This pH buffer must have an optimal action in the temperature range for sperm storage. Antioxidants are required as well, as these scavenge potentially harmful oxygen radicals. Oxygen radicals are built up during cell metabolism and can damage the components of the sperm membrane. Minitube semen extenders contain cell shield plus (CSP) a proprietary ingredient, that integrates into the sperm cell membrane and that efficiently protects the functionality of the membrane. CSP makes the membrane robust against temperature fluctuations and physical stress. CSP is very important during long term storage, for preserving the fertilization potential of a sperm cell.
The most controversial discussed ingredients in boar semen extenders, are the antibiotics. On one hand, they have to be included in semen extender by law (EU semen regulation 2016/426), on the other hand the general use of antibiotics is responsible for antibiotic resistance of many bacteria that are pathogenic in animals and humans. Due to the legislation, the use of antibiotics cannot be completely omitted in boar semen extenders, but their concentration can be reduced by 50%, without losing the efficacy of action against bacteria. This is possible by adding another proprietary supplement (OBS; organic bactericidal supplement), that is effective against a wide range of bacterial strains. The OBS even allows antibiotic-free storage of porcine semen doses at 17°C under certain circumstances [1], but this is currently not allowed, if the semen doses are produced for intra-community transport in the European Union.
Not all boar studs require all components in the same extender and therefore Minitube offers different semen extenders with different preservation capabilities. Table 1 summarizes the preservation functions of Minitube’s range of long-term semen extenders for boar sperm.
Table 1: Protective function and ingredients in Minitube’s long term boar semen extender
* Variants of Androstar® Plus and Androstar® Premium are available with OBS.
References
[1] Luther AM, Nguyen TQ, Verspohl J, Waberski D. Antimicrobially active semen extenders allow the reduction of antibiotic use in pig insemination. Antibiotics 2021;10. https://doi.org/10.3390/antibiotics10111319.
During the preparation of the semen doses, the native boar ejaculate is divided into many small parts. Each of these parts, which will later become the semen doses, must be extended to a minimum volume e.g., 80 ml for cervical AI and some 50 ml for post-cervical AI. The minimum volume of an AI dose is necessary as the sow’s uterus requires a minimum volume of liquid, so that the sperm cells can be transported via peristaltic movements towards the site of fertilization in the oviducts. The liquid of the semen dose works as carrier liquid for the sperm cells here.
Beside increasing the volume of a semen dose, the semen extender also needs to preserve the functional characteristics of the spermatozoa and must maintain an optimal fertility level. The sperm cells in a semen dose are exposed to many stressors on their way from semen collection, until the process of insemination. The semen extender has to protect the sperm cells against these stressors. Typical stressors include the transport of the semen dose from the boar stud to the sow farm. The transport distance and time can be quite significant and last several days. During this time the semen dose experiences e.g., temperature fluctuation, mechanical stress, and light exposure. Other stress factors for the sperm cells in the semen dose are metabolites and bacteria in the liquid semen and their metabolites as well. The dilution itself causes stress for the individual spermatozoa, as the diluent replaces the native environment of the sperm cells with semen extender.
Modern and especially long-term semen extenders, include several components to preserve the sperm function against the stressors. First, a pH-buffer is needed to stabilize the pH-value during storage. This pH buffer must have an optimal action in the temperature range for sperm storage. Antioxidants are required as well, as these scavenge potentially harmful oxygen radicals. Oxygen radicals are built up during cell metabolism and can damage the components of the sperm membrane. Minitube semen extenders contain cell shield plus (CSP) a proprietary ingredient, that integrates into the sperm cell membrane and that efficiently protects the functionality of the membrane. CSP makes the membrane robust against temperature fluctuations and physical stress. CSP is very important during long term storage, for preserving the fertilization potential of a sperm cell.
The most controversial discussed ingredients in boar semen extenders, are the antibiotics. On one hand, they have to be included in semen extender by law (EU semen regulation 2016/426), on the other hand the general use of antibiotics is responsible for antibiotic resistance of many bacteria that are pathogenic in animals and humans. Due to the legislation, the use of antibiotics cannot be completely omitted in boar semen extenders, but their concentration can be reduced by 50%, without losing the efficacy of action against bacteria. This is possible by adding another proprietary supplement (OBS; organic bactericidal supplement), that is effective against a wide range of bacterial strains. The OBS even allows antibiotic-free storage of porcine semen doses at 17°C under certain circumstances [1], but this is currently not allowed, if the semen doses are produced for intra-community transport in the European Union.
Not all boar studs require all components in the same extender and therefore Minitube offers different semen extenders with different preservation capabilities. Table 1 summarizes the preservation functions of Minitube’s range of long-term semen extenders for boar sperm.
Table 1: Protective function and ingredients in Minitube’s long term boar semen extender
* Variants of Androstar® Plus and Androstar® Premium are available with OBS.
References
[1] Luther AM, Nguyen TQ, Verspohl J, Waberski D. Antimicrobially active semen extenders allow the reduction of antibiotic use in pig insemination. Antibiotics 2021;10. https://doi.org/10.3390/antibiotics10111319.
