Cell Shield Plus™ (CSP™) was first discovered by Minitube in 2008 to provide cold shock protection for sperm cells. This macromolecule is known for its cell membrane stabilizing properties, proving to be beneficial for many medical/pharmaceutical and biotechnology applications. As an active ingredient in boar semen extenders, CSP’s™ properties protect the membranes and functions of sperm cells to maintain their full fertilization capacity.
Boar semen is known to be extremely temperature sensitive and quickly suffers various degrees of damage when subjected to temperatures below 15°C. With CSP™, this damage is almost entirely prevented, even at storage temperatures as low as 10°C over several days. Fertility trials have been completed and show that sperm stored at 10°C in Androstar® Plus maintained higher motility for up to 96 hours of storage and increased litter size by 0.47 live born piglets in a 778 sow trial.
Feedback from the field has been very positive for all Minitube extenders containing CSP™. Minitube offers 4 semen extenders containing CSP™, including 10 day storage term extenders: Androhep® ApX² Plus and EnduraGuard® Plus, as well as 7 day storage term extenders: Androstar® Plus and Androhep® Plus.
Further scientific studies have now demonstrated two additional benefits of CSP’s™ ability to stabilize membranes:
1. CSP™ protects sperm cells from damage when exposed to low or high temperatures
Table 1 shows the results of 12 ejaculates extended with Androstar® Plus, which have been exposed to different temperature conditions for up to 7 days. Analysis of progressive motility and integrity of acrosomes show an average of over 80% in progressive motility and 90% or more intact acrosomes with all treatments up to day 7. The temperature conditions of treatments 4 and 5 are especially significant because they mimic the common conditions of shipped semen. In everyday practice, the actual temperature of semen during transport often fluctuates outside the conventionally accepted temperature range of 15°C to 18°C due to high and/or low ambient temperatures. Upon arrival, semen is kept at the ideal temperature of 17°C until the day of AI (here day 7 = day of the analysis).
| Treatment | 1 | 2 | 3 | 4 | 5 |
| 25°C | 17°C | 10°C | 25/17°C | 10/17°C | |
| % Progressive Motility Day 3 | 86.3 | 89.8 | 85.9 | 89.6 | 87.6 |
| % Progressive Motility Day 7 | 82.6 | 90.4 | 86.0 | 89.9 | 86.4 |
| % Intact Acrosomes Day 3 | 94.6 | 95.3 | 91.5 | 95.4 | 92.6 |
| % Intact Acrosomes Day 7 | 92.4 | 93.2 | 89.6 | 94.3 | 91.6 |
Table 1: Progressive motility and acrosome integrity of semen extended in Androstar® Plus, having been exposed to constant storage temperatures at 25°C, 17°C and 10°C for 7 days, as well as varying storage temperatures of 24 hours at 25°C (treatment 4) or 10°C (treatment 5) followed by 17°C up to day 7 (n=12 ejaculates).
2. CSP™ avoids damage to sperm cells when high dilution rates are applied
It is well known that high dilution rates provoke lower storage ability and fertility of boar semen due to the decrease of seminal plasma in relation to sperm. Table 2 shows the average impact of high dilution rates on progressive motility and acrosome integrity in 6 ejaculates. When compared to an extender without CSP™ (BTS), the sperm cells conserved in Androstar® Plus suffer considerably less on both quality parameters. Acrosome integrity remains intact with an outstanding average above 90%, even after 5 days of storage. This is due to the CSP™, which has proven to compensate for the otherwise detrimental high dilution of seminal plasma in ejaculates with high sperm cell concentrations.
| BTS 2.5 billion | Androstar® Plus 2.5 billion | BTS 1 billion | Androstar® Plus 1 billion | |
| % Progressive Motility Day 3 | 84.3 | 91.1 | 72.3 | 82.7 |
| % Progressive Motility Day 5 | 78.2 | 89.0 | 53.7 | 70.2 |
| % Intact Acrosomes Day 3 | 93.2 | 97.2 | 88.7 | 94.6 |
| % Intact Acrosomes Day 5 | 90.4 | 95.8 | 85.5 | 93.2 |
Table 2: Effect of high dilution rates (2.5 and 1 billion semen cells/80ml) and extender (BTS vs. Androstar® Plus) on progressive motility and acrosome integrity (n=6 ejaculates, storage temperature 16°C).
All "Plus" boar semen extenders produced by Minitube now contain the CSP™ component which effectively opens the temperature window from 10°C to 25°C (50°F to 77°F). Now, for the first time, the limiting temperature window from 15°C to 18°C, previously necessary during shipping and storage, has been expanded significantly.
With CSP™, Minitube’s research is once again offering the most advanced boar semen extender technology, exclusively available in all “Plus" extender products. Minitube’s “Plus” extenders, the next revolution in facilitating lower sperm cell concentration in the field, thereby increasing and maximizing the production of semen doses of all AI boars.
Trials are currently being finalized to further demonstrate the beneficial properties of CSP™, facilitating further advances in boar semen preservation technology by eliminating the need to immediately cool boar semen to the conventionally accepted target temperature of 17°C.
Scientific publications will soon be available to provide more detailed technical information about this exciting innovation in boar semen preservation.