The timing of the artificial insemination (AI) of sows is important. There are ways to determine when to inseminate sows. The sow should be tested for a standing reaction (this should be performed twice daily). A sow stands more readily to back pressure when she can see, hear and smell a mature boar and when nose-to-nose contact is possible through a pen division.

Detecting the oestrus cycle is critical to timing of insemination. Briefly, insemination of the sow should occur twice. Once between 8 and 12 hours after the handler first gets the standing reaction and again 8–16 hours later.

If inseminating only once, it should be done 24–32 hours after the onset of standing heat. In practice, this insemination can be performed when checking for standing heat (twice daily). Inseminate about 24 hours after the sow stands to back pressure.

Successful timing of insemination

One of the most important factors that can affect the fertilisation rate and the success of an AI pig breeding program is the timing of insemination.

During ovulation, the ovaries shed eggs (ova) for 40 hours (this can range from 36–50 hours) after the onset of oestrus. Spermatozoa (freshly collected or chilled semen) have to mature for 2–3 hours in the female oviduct before they are capable of fertilisation.

After mating spermatozoa can be found in the oviducts of naturally mated sows for 24 hours or more.

Ova have a much shorter lifespan. In the oviduct, they are viable for less than 6 hours. Ideally, eggs should be fertilised within hours of being shed, as embryos created from older eggs tend to die more readily.

To achieve an optimum conception rate:

• inseminations with fresh or chilled semen should occur approximately 12 hours before ovulation
• insemination at 28 hours (about a day) after onset of heat should be performed (this is the best time as ovulation occurs approximately 40 hours after onset).

As the exact time of the onset of oestrus is difficult to pinpoint on-farm, inexperienced handlers should perform 2 inseminations (12–16 hours apart) to achieve the best results.