Artificial Insemination (AI) of swine is common. We have used AI exclusively since 1994 to incorporate new genetics into our herd. While it is not difficult, a little information can increase your chance for success.
We use no reproductive drugs to assist in breeding. Consequently, we only AI sows as they exhibit a more consistent estrus compared to gilts. Estrus is when a sow is fertile and will allow herself to be inseminated.
Swine semen is usually collected and shipped fresh, not frozen. It will stay viable for about a week after collection, but its potency is reduced as it ages. So it is important to synchronize estrus in the sows you want to inseminate so the semen will be used promptly.
The best way to synchronize estrus in sows is weaning. Sows consistently exhibit estrus 4-7 days after weaning. We wean the sows 4 days before our semen arrives.
The boar stud we use is Swine Genetics International (SGI). SGI collects its boars on Mondays and Thursdays. Semen is shipped next day air UPS and will arrive at the farm on Tuesdays or Fridays. So we wean sows on Fridays or Mondays.
Sows are housed as a group adjacent to a boar or boars. The sight and phermones of a boar stimulates return to estrus. If a boar is not available, an aerosol can of boar phermones can be used. Sows are fed ad libitum, (all they can eat).
Sows will begin to act squirrelly as they approach estrus. They will vocalize more and begin pacing around the pen. Their vulva will swell.
On the afternoon of the second day the boar is removed, preferably to another building. If the boar is allowed to remain next to the sows it will make estrus detection more difficult. This is because sows tend to fluctuate throughout the day in their expression of estrus. They will exhibit estrus strongly for several minutes, get tired, and then lie down and rest. If you are not observing constantly you will miss estrus detection in some sows.
On the morning of the third day, the morning before the semen arrives; we move a boar back within walking distance of the sows. We use our hydraulic trailer, which lowers completely to the ground, and have the boar locked in the front. We let two sows out of their pen at a time and gently walk them towards the boar. If they are in estrus they will stop by the boar and lock their legs. This is called ‘standing heat’. Often, their ears will waggle and they will emit a characteristic growl.
To test for standing heat, put some weight on the sow’s back with your hand. If the sow is in estrus she will stay locked in one place. If she is not in estrus she will try to move away from your pressure.
We wait and watch for a couple of minutes. Sometimes a sow will take a few minutes to lock into standing heat. If a sow is in estrus, she receives a chalk mark. If I suspect a sow is close to being in estrus she receives a different colored chalk mark. The sows are removed from the boar and put back into another pen. This continues until all of the sows are heat checked. We check for estrus twice a day, as close to twelve hours apart as possible.
Why don’t we just let the boar stand by the sow’s pen and observe the sows in their own pen? Some sows are less aggressive and will not exhibit estrus in this situation because they don’t want to crowd next to the more dominant sows which are standing near the boar.
Research has shown that on average, sows ovulate 40 hours after the onset of standing heat. To become pregnant, live sperm need to unite with ovum. Timing is the crucial element for successful insemination.
Once a sow is observed in standing heat, she is inseminated 24 hours later. She is inseminated a second time 12 hours after that. If observation of standing heat was accurate, this protocol should result in live sperm uniting with ovum.
Insemination is similar to heat detection on our farm. A boar is placed in the front of the hydraulic trailer. Two sows we want to inseminate our let out of their pen and shut in the back of the trailer. They should still be in standing heat and will lock themselves in place which makes it easy to work with them. A trick we use if a sow is uncooperative is to place a little feed on the floor of the trailer.
We use a paper towel to clean off each sow’s vulva. We then insert a breeding rod into each sow’s vulva angling the rod upward so it doesn’t enter the bladder. We use a foam- tipped breeding rod. Some rods are corkscrew shaped to resemble a boar’s penis. You must turn these rods counter-clockwise as you enter the sow’s cervix.
We gently push the foam-tipped rod into the sow until we feel we’ve entered the cervix. Gently tug the rod backwards. If there is some resistance, you are in the cervix and ready to inseminate. If the rod slides back easily you need to reposition.
The boar semen is in single serving plastic bottles designed to inseminate one sow. Boar semen is priced from $5 to $250 per bottle. We have found a way to stretch our dollar that seems to not affect conception rates or litter size. If we have two sows in heat at the same time we will use a half bottle for each sow.
Boar semen needs to be kept at 64 F until used. We store it in a double cooler in our basement. We also use a cooler to transport it to the breeding area.
We take a bottle of semen out of its cooler and cut off the tip with a pocket knife. We put the bottle in the end of the breeding rod and apply very gentle pressure. If a sow is expressing estrus well, she will actually have contractions that can suck out the contents of the bottle in a minute or less. This is almost too fast though and we are not concerned if it takes five minutes. If we are splitting a bottle we remove it from the rod when it’s half empty and use the rest on the other sow.
When finished, we pull out the rods and discard. We don’t reuse as this will prevent passing an infection between sows. Rods are priced at about 50 cents a piece.
Sows are returned to their pen. It is important to not overfeed sows the first month after breeding as this has been shown to reduce conception rates and litter size. We reduce their feed intake to about five pounds. It is also important to not stress sows for the next month. If they need to be moved to a different pen or group, moving immediately is best.
We have had conception rates from 50% to 100%. The average is around 70%. We have had the most success breeding in the March through May period. August is the worst month for successful breeding. We have not used AI in the coldest winter months as our facilities are outside and we are afraid the semen would freeze.