By Dr Dorothea Mostert, CS Vet
As with all things in life, it is the little things that count, 45µm to be exact. This is the average size of one porcine sperm. Making use of extended semen and artificial insemination is widely practiced and an excellent way of ensuring that your farm obtains the latest genetic gain.
To optimise the genetic advantage, it is of utmost importance to handle the semen correctly from production right through to AI.At the AI station, the semen is processed and packaged in a highly controlled manner and made ready for dispatch. The semen is extended with a scientifically developed extender, which includes nutrients, electrolytes, buffers and sometimes also an antibiotic. It creates an ideal environment for the sperm to survive in and still be viable at time of insemination. Different types of extenders are used, giving variable shelf lives, from 3 to 10 days. The semen is cooled to and packaged at 17°C.
17°C is the magical number that should be maintained until the sachet is attached to the AI catheter. At 17°C the metabolism of the sperm inside the sachet is slowed down to a rate that will ensure that it stays alive and able to fertilise the ova. Getting from the AI station to the sow, the semen needs to be handled without any errors to ensure that it gives the desired result. A 2-3°C fluctuation in temperature to either side can decrease the shelf life of the sachets by up to a day.
If the temperature is higher than this, for example 20°C, the metabolism speeds up and the sperm is more active, using up precious energy. Metabolism also creates byproducts that can be harmful to the sperm. Semen stored at this higher temperature will not be viable for the expected period that the manufacturer has determined. At temperatures lower than 17°C, for example 13°C, the membranes around the sperm get damaged. Although they will still be able to swim normally, they will not be able to fertilise the ova.
As the temperature needs to be maintained from dispatch to delivery, semen is transported as soon as possible after packaging, in insulated containers. It can be of great benefit to the farm to have a temperature logger travel with their shipment. From this device data can be retrieved to see the exact temperature the package was kept throughout the journey. Doing this, errors can be picked up before a whole week’s production is lost.
When receiving the packaged semen on farm, it should be transferred to a semen fridge immediately. Old doses should be discarded before restocking the fridge. Pack fresh doses loosely to allow cool air to circulate. The semen fridge must be clean and in good repair. A high quality fridge that uses a forced air system and can both heat and cool is the gold standard. Putting a temperature logger inside and reading it on a regular basis can alert you to a problem in time. A minimum maximum thermometer can be used as an adjunct or alternative.
It is important to keep the opening of a semen fridge to a minimum as the temperature needs to stay as constant as possible. Sachets should be turned twice a day to re-suspend the sperm. As the sperm floats down under effect of gravity, they form a concentrated area at the bottom of the bag where they have little access to the nutrients provided in the extender. When handling the sachets, touching the sachets with your hands should be kept to a minimum as this increase the temperature.
Taking your required amount of doses in an insulated container to the service house must be done just before service. It is essential to avoid exposing the semen to sunlight as the UV rays will destroy the sperm. As the semen enters the reproductive tract during service, it warms up to the sow’s body temperature and through a process called capacitation, gets ready to fertilise the ova. Refrain from returning unused sachets to the fridge as they may have experienced temperature fluctuations and are now of inferior quality.
The better semen handling and storage is controlled up to service, the better chance the semen in the sachet has to give you successful results.