Swine AI Guidelines for Beginners
Advantages of Using Artificial Insemination
There are several advantages to using artificial insemination (AI) in swine operations. First, few to no boars are needed, therefore alleviating the cost of feed, housing and medical supplies for intact males. Second, it can save time and labor during breeding and farrowing season when coupled with estrus synchronization. Finally, with proper management, time commitment and skill, you can improve herd quality with access to genetically superior boars while maintaining biosecurity on the farm.
The key to a successful AI program is detecting estrus (standing heat) in the gilt or sow. Females typically cycle every 21 days, but estrus cycles can vary. Cycles may range from every 16 to 25 days.
Signs of Estrus
- Swollen, red vulva
- Increased vocalizations
- Decreased appetite
- Pinning of ears
- Mucus discharge from vulva
- Mounting other females or standing to be mounted
It is ideal to heat check females every 12 hours by using a mature boar or sex odor aerosol (boar spray). Depending on the facilities, either allow the boar in the area with the female(s) for direct contact or allow the boar to stand on the outside of the pen and allow each female to smell the boar. Once the female approaches the boar, apply pressure to her back by pushing or gently sitting on her to detect estrus. If she “locks” into position by becoming immobile and pins her ears erectly in a forward position, she is in standing heat. If the female is not in standing heat, she will attempt to escape when pressure is applied to her back. Gilts typically exhibit estrus for an average of 38 hours and sows for 53 hours. It can be very helpful to keep records of estrus cycles on each female to maximize conception rates.
Synchronizing Estrus Cycles in Females
Synchronizing your females can be beneficial for time and financial management during both breeding and farrowing. There are natural and synthetic methods to synchronize sows or gilts.
Weaned Sows: Wean suckling piglets off sows all on the same day. It is suggested to wean piglets at three to four weeks of age. Sows will typically come into estrus four to seven days after weaning.
Prepubertal Gilts: Mature age for the reproductive tract in swine is around 160 days, but gilts typically don’t start cycling until around 200 days. To start estrus in prepubertal gilts (160 to 180 days old), there are several methods.
- Transport Method: Transporting gilts from one farm to another or mixing of prepubertal gilts can cause the onset estrus within five to seven days.
- Boar Method: Exposing gilts to the sight, scent, sound and physical presence of a mature boar (over 12 months of age) for at least five to 10 minutes daily can cause estrus typically within 10 to 14 days. Most operations will use both the transport and boar methods to increase success of estrus in prepubertal gilts.
- Using PG600: This pharmaceutical compound is a combination of two, naturally occurring hormones – equine chorionic gonadotropin (pregnant mare serum gonadotropin) and human chorionic gonadotropin. Gilts can show signs of estrus within five to 10 days after treatment. This method is often used with the boar method for best results. Typically, waiting to breed gilts until the second to third estrus cycle will maximize the number of ovulations and increase litter size.
Sows and Cycling Mature Gilts: Once females reach puberty and begin to exhibit normal estrous cycles, boar exposure and PG600 cannot be used to synchronize estrus due to a hormone called progesterone. Therefore, strategies for synchronizing estrus in mature sows and gilts need to create a situation in which the decrease or removal of progesterone occurs at the same time in all animals.
A synthetic product is approved and available on the market by the name of Matrix. Recently, similar products containing altrenogest have been approved and made available for use. Matrix is manufactured by the company Intervet/Merck Animal Health. Matrix can be used at any stage during a female’s estrous cycle and is administered orally at 6.8 milliliters (15 milligrams altrenogest) per female daily for 14 days. Treat gilts on an individual animal basis by top-dressing Matrix on a portion of each gilt’s daily feed allowance. To produce the desired synchronization of estrus in a group of gilts, treat all of the gilts daily for the same 14-day period. Typically, 85% to 90% of females treated with Matrix show signs of estrus within four to nine days – most often five to seven days after the last dose.
Inseminating Gilts and Sows
Females should only be bred when in standing heat. Females need to be inseminated before ovulation; however, it is hard to detect exactly when a female will ovulate. Therefore, it is recommended to inseminate females twice during standing heat for higher conception rates and larger litter size. Sows typically stand longer than gilts, but it also can depend on genetic makeup, environmental factors and individual females.
Ovulation occurs at the end of the estrous cycle in both gilts and sows. Suggested guidelines for insemination in gilts is 12 hours after the first detection of estrus. A second insemination should follow 12 hours after the first. Sows should be inseminated 24 hours after the first detection of estrus and a second insemination should occur 12 hours later. If a female stands for three days, a third insemination may be beneficial for optimum timing of ovulation and success in conception.
The insemination process on gilt or sow is fairly easy with a little practice.
- AI breeding rods
- Non-spermicidal lube
- Rag or damp paper towel
- Mature boar or boar spray
There are several types of inexpensive, disposable AI breeding rods to choose from, such as foam-tipped, spiral and deep uterine. Choose which works best for your operation and preference.
Steps to Take
- Bring a boar to the female, place the boar in an adjacent pen and allow nose to nose contact. If a boar is not available, use boar spray and spray on the female’s snout. “Acting” as a boar may be needed, such as pushing on her shoulders, sides and back.
- Check to see if the female is in standing heat by applying pressure to the females back. The “locked up” standing heat position will allow for the hormone oxytocin to be released, causing contractions of the uterus to transport semen into the uterus and oviduct.
- Clean the vulva with a rag or damp paper towel to prevent any debris from entering the reproductive tract.
- Lubricate the tip of the breeding rod with non-spermicidal lube or a few drops of the semen.
- Insert the breeding rod in the vulva at a slight upward angle, toward the female’s back, to prevent the rod from going into the bladder.
- If using the spiral-style breeding rod, gently turn the rod counterclockwise while inserting it into the vagina and cervix. The tip of the rod will “lock” into the cervix. The rod is typically inserted 8 to 10 inches before reaching the cervix. To test for the locked position, twist the breeding rod counterclockwise and release it. The rod will rotate back clockwise about a quarter of a turn if the rod is locked in the cervix. If you are experiencing difficulty getting the rod to lock, reposition the rod and try again. Be patient.
- If using a foam-tipped breeding rod, turning the rod counterclockwise is not necessary. Gently insert the foam tip the same way until you feel a “pop.” The rod will catch in the folds of the cervix. To test for the locked position, gently pull back on the foam-tipped rod to ensure it is caught in the cervix. Typically, if you hit the bladder, there may be urine backflow, or the female will be uncomfortable and move around. If this happens, be sure to remove the breeding rod and use a new one.
- Once the rod is locked into the cervix, gently mix the semen bottle. Snip the end of the bottle and insert it to the end of the breeding rod. Gently squeeze the bottle of semen to start the flow into the cervix. The female may take in the semen herself due to the contractions of the uterus. Be patient, this process could take up to five minutes. Work with the female and apply gentle pressure to the bottle as needed. A small amount of semen backflow is normal at the vulva; however, if there is a good amount of backflow, stop and reposition the rod and try again.
- Once the bottle is empty, remove the spiral rod by gently pulling it out while turning it clockwise. The foam-tipped rods can just be gently pulled back out.
- Once the rod is removed, continue to apply pressure to the females back with a boar in close proximity or use the odor spray to allow for continued contractions.
- Repeat the procedure and use a new breeding rod for any consecutive inseminations on the female or other females.
After the final breeding, check for standing heat 12 and 24 hours later. If the female is no longer standing after 12 hours, the optimum timing was likely achieved. If she is still standing administer another dose of semen. If the female is still standing after 24 hours and no doses of semen are available, the optimum timing was likely missed. If only a single dose of semen was administered and the female is no longer standing after 12 hours, optimum timing was likely met.
Do not try to administer a second dose of semen if not standing, this could have adverse effects on the breeding. Be sure to heat check on the females’ next estrous cycle dates. Recordkeeping is vital for a successful management plan. Keep records on breeding dates, estrous cycles, due dates, boars used, etc.
Proper Semen Handling
Proper handling and storage of semen is crucial to keep the quality of semen and conception rate high. Boar semen can be obtained from a boar stud or a reputable semen seller. There are plenty of operations and price options to choose from. Research each to find what suits your needs. Boar semen is typically collected two times a week to ensure high quality semen. An extender is mixed with the semen to allow the semen to live longer – fresh semen without an extender will only live for about 30 minutes.
Boar studs will ship cooled semen mixed with an extender in a cooler with gel packs using next day delivery. Keep semen at 60 to 65 F – 63 F is ideal. DO NOT put it in the fridge or freezer – this is too cold and will cause the semen to go into shock. Fluctuations in temperature will cause a shorter lifespan of semen.
Some producers use a wine cooler or place semen containers in the basement. A best practice is to keep a thermometer with the semen to ensure proper temperature. Discuss with the boar stud about what temperature they keep semen or other possible options to store semen until ready to use.
Tips for Keeping Semen Viable
- Gently rotate semen twice a day to suspend the semen and mix it with the extender, do not shake.
- Do not expose semen directly to sunlight.
- Semen with extender is typically viable for up to seven to nine days. Discuss with the boar stud the extender they use and typical lifespan of the semen for each boar.
- Personally check the quality of semen with a microscope.
Artificial insemination (AI) offers several advantages over natural breeding, such as genetic improvement, ability to choose from a wide selection of boars, fewer boars needed, and the financial and time management resources. The keys to a successful AI program are detecting and recording estrous cycles and proper semen handling. Estrous cycles can be synchronized in females and AI allows multiple females to be bred at the same time. The procedure of AI is fairly simple and can easily be learned with some practice.
Tasha Harris, WVU Extension Agent - Upshur County
Jesica Streets, former WVU Extension Agent - Tucker County
Board, N. (2015, October 08). Heat Detection. Retrieved September 04, 2020, from
Board, N. (n.d.). Swine Inseminator's Handbook: A Breeding Technician's Guide to
Inseminating Swine. Retrieved September 04, 2020, from https://porkgateway.org/resource/swine-inseminators-handbook-a-breeding-technicians-guide-to-inseminating-swine/