For all practical purposes, your breeding herd staff cannot control the standard operating and quality control procedures of semen-supplying boar studs.

They can, however, have a huge impact on the storage, handling and use of the boar semen after it arrives, states Kevin Rozeboom, director of research and education at Minitube of America, Verona, WI.

Reproductive performance, no matter what your measure of success, requires that an ample number of viable sperm cells be inseminated in the sow or gilt, he adds. Rozeboom addressed swine practitioners at the mid-September Leman Swine Conference in St. Paul, MN.

From semen collection and processing in the boar stud to the semen handling and insemination process in the sow herd, there is a multitude of opportunities for the process to run amuck.

The reproductive process is a complex one, Rozeboom admits, “but the number of viable sperm cells is the key.”

Steady Temps

Throughout the evaluation and processing of fresh boar semen, it is very important to maintain a constant temperature. But once it is extended and packaged, it is ready to be cooled to 63° F. (17° C.), the optimal storage temperature for fresh boar semen, he explains.

“The cooling process causes a gradual and constant reduction of metabolic activity to conserve sperm cell energy and viability,” Rozeboom points out. “Cooling reduces the risk of depleting the buffer and the nutrients provided by the semen extender. Once semen is cooled, it should be maintained at 63° F. until it is used for insemination.

“For each temperature fluctuation, up or down, of 3.6 to 5.4° F. (2-3° C.), sperm cell viability and shelf life may be decreased by as much as one day,” he says. “In short, when properly cooled and stored at a consistent 63° F., sperm cells will remain viable for a longer period of time.”

Suppliers' Quality Control

Breeding herd managers should verify their suppliers' quality control standards before boar semen is released to the farm, Rozeboom says. These standards should include monitoring of the analytical and hygienic procedures in the laboratory. Each semen batch should be quality-control tested after the semen is extended, then again after the semen is packaged (Day 1).

The quality-control evaluation of semen dose samples is the same as that used in the ejaculation evaluation procedure used to calculate the number of viable sperm cells per dose. The number of viable sperm/ejaculate is calculated using this formula: % gross motility × % gross morphology × total sperm cells = viable sperm.

For example, if the ejaculate displays 90% gross motility, 72% gross morphology and 70 billion sperm cells, 45.4 billion viable sperm cells are present (i.e. 0.90 × 0.72 × 70 billion = 45.4 billion.)

To calculate the number of doses/ejaculate, divide the total number of sperm cells by the number of viable sperm cells required per dose (i.e., 3 billion). Therefore, in the example above, 45.4 billion divided by 3 billion would equal 15.1 potential artificial insemination (AI) doses.

Rozeboom offers this quality control standards checklist for breeding herd managers:

  • Check AI doses for consistent volume (>70 ml.).

  • Test semen for sperm cell concentration, total sperm number, gross motility and gross morphology to calculate and confirm that each dose has at least 2.5 billion viable sperm cells at the time of insemination. Use the ejaculate evaluation procedures outlined above.

    “Acceptable results confirm that the initial evaluation of the ejaculate and the processing procedures were correct and the semen was properly handled,” Rozeboom notes. “Failure to meet these minimum standards indicates a deficiency and a potential to cause an inconsistency in reproductive performance, in which case the semen batch should be discarded.”

  • Evaluate sperm cell agglutination or sperm cell clumping. If more than 25% of the cells show clumping, the semen should be discarded.

  • Conduct quality control testing on Days 1, 3, 5, 7 and 10 (depending on the extender used) to ensure sufficient viable sperm cells.



Semen Shipping Standards

No matter how well semen doses are prepared, if they are not carefully transported, their reproductive performance is jeopardized. Whether transported by commercial carrier or in-house staff, the basic goals include gentle handling, stable semen temperature and minimal cost.

Rozeboom advises breeding herd managers to check their suppliers' shipping procedures:

  • Ship semen after cooling to 63° F.

  • Use insulated shipping containers that counteract ambient temperatures and minimize temperature fluctuation to no more than 1.8° F. (1° C.).

  • Use double-boxed containers, as they offer more insulation to maintain temperatures during increased delivery time and when environmental shipping conditions are more stressful. A small box containing the semen doses within the shipping container, often made of Styrofoam, can be surrounded by thermal packs. Air cavities within the boxes are filled with packing peanuts. This double packing insulates the semen doses from temperature fluctuations and protects them from rough handling.

  • Use high-low thermometers or data loggers to monitor temperature fluctuation. The high-low thermometers are the simplest, lowest-cost option and are limited to recording temperature highs and lows only. Digital data loggers monitor and record the temperature in the shipping containers and semen boxes at preset time intervals over a period of time. Data loggers are especially useful when temperature fluctuations during delivery are suspected as a potential cause for reduced reproductive performance, he notes.

  • Label shipping containers with “Live Semen Shipment.” Also, the shipping company should receive a handling protocol request for minimal thermal effect during transit, Rozeboom adds.



Boar Semen Storage Checklist

Once boar semen reaches the farm, the farm personnel accept full responsibility for proper handling and storage.

Kevin Rozeboom, director of research and education at Minitube of America, Verona, WI, offers this checklist for maintaining temperature and avoiding missteps in handling:

  • Record the arrival of all semen batches.

  • Use semen storage units with forced-air circulation that both heat and cool to maintain the crucial 63° F.

  • Do not warm semen once it has been cooled and equilibrated to 63° F.

  • Monitor the semen storage unit temperature daily. This is easily done by filling a bottle with 70 ml. (2.1 oz.) of water and placing it near the center of the semen storage unit. Simply insert a thermometer through the bottle stopper to obtain the daily temperature reading.

    “Thermometer readings confirm the accurate operation of the unit's temperature controller and digital readout or it will alert the technician to a possible temperature maintenance problem,” Rozeboom explains. “And, when temperature readings are taken, that is a good time to rotate semen doses.”

  • Do not overload storage units with warm semen.

  • Do not open the storage unit during the cooling process.

  • Use a high-low thermometer to record the high and low temperatures of the semen storage unit.

  • Store semen doses away from ultraviolet light.

  • Regularly clean the semen storage unit using a disinfectant such as Conflict or a bleach solution.

  • Do not return semen doses to the storage unit if their temperature has fluctuated more than 5.4° F. (3° C.). This holds true if the doses are temporarily removed from the storage unit and temperature fluctuations exceed the recommended range. Discard those doses.

  • Breeding herd managers should check semen doses for consistent volume (70 ml.), test semen for sperm cell concentration and number and check semen motility and morphology. Each dose should have a minimum 2.5 billion viable sperm cells.

  • Keep the semen storage unit in a temperature-controlled room, such as an office, with even airflow on all sides of the container. Avoid hot corners.

  • Plug storage unit into its own electrical circuit to avoid power surges and/or use a UPS surge protector.



“The bottom line for peak reproductive performance and profitability is setting and achieving high standards,” Rozeboom says. “Any compromise of these standards affects semen quality and causes reduction in reproductive performance.”