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Artificial insemination
Using artificial insemination (AI) can help manage the fertility and health of the pig herd and increase the success of the pig breeding business.
Learn about:
- how and when to use AI
- which equipment and techniques can be used
- detecting oestrus in sows
- timing of insemination.
Whichever method is used, successful AI relies on understanding the:
- process
- correct storage and handling of boar semen
- equipment used.
Artificial insemination process in pigs
When using semen collected on-farm or buying it from an artificial insemination (AI) centre, successful insemination depends on:
- detecting oestrus in sows
- insemination timing
- correct technique
- storing and handling semen correctly.
Detecting oestrus
During a sow’s 50–60 hour oestrus or heat period she will mate but she is only very fertile for 24–32 hours.
Familiarity with signs during proestrus, oestrus and peak fertility ensures that insemination can occur during the best possible time frame.
Timing
The timing of insemination of sows is central to success in an artificial insemination breeding program.
Sperm and eggs are viable for only a limited period of time, so to achieve the best results perform inseminations within these time limits.
Correct technique
Using the correct insemination technique increases your chances of success. The technique should imitate natural mating as closely as possible. For CAI cleaning the area around the sow’s vulva, manually stimulating the sow in the presence of a boar to induce the mating stance and careful insertion of the catheter will help to obtain a positive outcome.
When using the PCAI method the sow should be stimulated by a mature boar and then allowed to relax for 30 minutes before insemination procedures commence The vulva should be cleaned to ensure particles and micro-organisms are not passed into the uterine body.
Boar stimulation during insemination is not required.
Storing and handling semen
Use the correct equipment and take care of equipment when collecting boar semen.
AI success can be compromised by poor quality semen, due to:
- rough handling
- temperature changes
- delays in transport
- exposure to light.
Tips for success
- When handling the sow, be firm but not aggressive.
- Ensure staff are trained in the movement and handling of pigs.
- Implement sound workplace health and safety practices.
- If a sow or gilt first stands to back pressure in the morning when near a boar, inseminate late in the afternoon of the same day and again the following morning.
- If a sow or gilt stands in the afternoon, inseminate her the following morning and again late that afternoon.
- If only doing a single insemination, inseminate her the following morning and again late that afternoon.
- If mucous is present, it should be creamy in colour rather than clear. If it is clear, it is too early to inseminate.
- Use clean equipment for every insemination and ensure the sow is adequately stimulated before insemination.
- Carefully lock the catheter into the cervix and be patient and allow the semen to flow slowly.
- When using the CAI method, continue stimulating the sow during insemination and continue to handle the sow firmly but not aggressively.
- When using the PCAI method allow the sow to relax for 30 minutes after inter action with the spotter boar before commencing the insemination procedure.
- When using PCAI method do not stimulate sow by boar contact during insemination.
- Be alert for catheter blockages and semen back-flow.
- Record date and time of actions plus identity of inseminator for future reference.
Advantages and disadvantages of aritificial insemination of pigs
The success of a pig breeding business is dependent on herd fertility.
Purchase of semen from an AI centre or semen collection on farm enables owners and managers of piggeries to breed their animals through artificial insemination (AI). Artificial insemination provides herd owners and managers with the opportunity to introduce superior genes from top performing boars into the herd.
Advantages
- Semen from several breeds and from a range of top performing boars (that have been tested) is available from AI centres.
- Superior sire line genetics (i.e. the genetic influence of good boars) can be spread more widely across the herd.
- Compared with bringing in live pigs, AI is a safe, and cost-effective method of introducing new genes into pig herds, especially into herds classified as specific pathogen-free, minimal disease or high-health status
- It may be used during temporary shortages of boars due to death, lameness or refusal to work decreases the number of boars in the herd that are fit for service.
Disadvantages
- Semen is temperature sensitive and lower than average results can occur when chilled semen is stored for longer than 72 hours.
- Disappointing results can occur when AI is poorly timed or performed incorrectly due to operator fatigue.
- Delays in the transport of semen between the collection centre and the pig breeding facility will have an adverse effect on success rate.
Timing of artificial insemination of sows
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.
Equipment used in pig artificial insemination
Facilities in a successful artificial insemination (AI) operation should include:
- appropriately sized holding pens for sows (to test for oestrus away from other sows and to allow sows to rest post-insemination)
- a boar-holding pen with designed to allow nose-to-nose contact with sows
- good lighting and a non-slip surface
- facilities for disposal of waste
- Personal Protection equipment (PPE) to reduce the risk of injury to or infection of the stockperson.
Catheter
- reusable rubber 'Melrose' with a spiral tip or disposable plastic catheters with several types of tip are commonly used for AI (all are easy to use and achieve good results)
- many inseminator staff prefer catheters with spiral tips that lock in (like the boar's penis) and reduce back-flow during insemination
- non spermicidal lubricant.
For post-cervical artificial insemination (PCAI), a catheter similar to a sponge tipped rod catheter is inserted through the vulva into the cervix. The semen is deposited into the uterine body by a sleeve that extends 200mm beyond the end of the rod catheter.
The disadvantage of reusable catheters is that scrupulous cleaning and hygienic storage is required between uses.
Semen bottles and tubes
Chilled semen bought from AI centres comes in ready-to-use inseminating bottles or tubes. A supply of clean plastic inseminating bottles is needed if semen is collected and used fresh or diluted on-farm.
Cleaning and storage
- Keep equipment clean (boar semen is an excellent medium for bacterial growth)
- Soak reusable equipment in cold water immediately after use so that semen or other material can be easily removed later
- Do not use soaps or detergents when cleaning equipment because they affect sperm viability
- Remove particles of gel with a brush
- Rinse, then boil rubber 'Melrose' catheters in distilled water for 10–20 minutes before reuse
- Do not use tap water for rinsing because it leaves mineral deposits on the equipment
- Store equipment in a dust-free cabinet or when completely dry, in a sealed plastic bag
Detecting oestrus in breeding pigs
Identification of oestrus needs to be carried out each day. A sow is in oestrus ('heat') for 50–60 hours and will mate during that time, but she is only very fertile for 24–32 hours.
Signs of oestrus
Proestrus
The period before oestrus proper lasts 2–4 days. The signs of approaching oestrus include:
- the sow mounting others when she is in a group
- swelling and reddening of the vulva (there is little mucous secreted from the vagina at this stage)
- sows honking, losing their appetite and appearing nervous and restless
- the sow looking for the boar.
Oestrus
The signs of the onset (beginning) of oestrus include:
- the sow accepts the boar's sexual advances (i.e. 'stands' or stands still)
- the vulva is still red and swollen and watery mucous is seen often after sexual stimulation
- the ability of only the boar to get the sow to stand and insemination (at this time) results in poor fertility.
Peak fertility
- Occurs in the middle of 24 hours of oestrus (i.e. it starts about 12 hours after the onset of oestrus)
- Boar and trained staff member can get a strong standing reaction (standing heat) during this time
- Swollen, red vulva has noticeably subsided
- Plenty of mucous and it has better lubricating qualities than the mucous that is produced at the beginning of oestrus
- Mucous colour changes from clear to greyish at peak fertility
- Sow stands for the boar in the last 12–24 hours but is less inclined to do this for the handler
- Insemination in the last 12–24 hours gives poor results.
Identifying oestrus by the presence of a boar
Oestrus in a sow may also be detected by the presence of a boar:
- introduce the boar and allow nose-to-nose contact with the sow
- allow the boar to attempt to mount the sow (this could take up to 2 minutes).
The boar should be removed if the sow does not stand or if she attempts to bite or fight the boar. Also, separate the sow and the boar if oestrus detection is for the purpose of using AI.
Techniques for artificial insemination
Use the right artificial insemination (AI) technique to increase the chances of obtaining the best results for the breeding program. The technique should imitate natural mating as closely as possible.
The uterine horns of a mature sow are up to 1.5m in length. Spermatozoa cannot travel this distance without help. Oxytocin secreted from the sow's brain in response to stimulation causes smooth muscles in the tract to contract. This pushes the spermatozoa towards the oviduct and is critical for successful insemination.
There are 2 methods of inseminating the sow:
- introduction of semen into the cervix (CAI)
- post-cervical (PCAI) or intra uterine method.
CAI method
The CAI method uses the reusable Melrose rubber spiral tipped catheter or disposable spirettes with anti-clockwise threads or a foam tipped catheter.
The catheter is inserted through the vulva to lock with the cervix. The semen is deposited at the cervix and the contraction of the uterus moves the semen along the uterus. The success of CAI is increased significantly if the sow is being stimulated by contact with a mature boar when being inseminated to encourage contraction of the uterus.
The CAI method results in high wastage of spermatozoa as it travels to the ova.
When using the CAI method:
- insemination should only take 5 10 minutes when a sow is well stimulated
- it's possible to let the semen gravity-feed into the catheter when using soft-walled bottles (gentle pressure may be used with any type of bottle, particularly the firmer types)
- back-flow may occur if the catheter is not inserted far enough or the trained staff member is too hasty. If this occurs, disconnect the bottle, reposition the catheter and delay insemination for 1–2 minutes
- semen is often squeezed out by abdominal pressure when the sow suddenly moves (e.g. when coughing or struggling)
- a small back-flow is not unusual and not detrimental provided enough semen with an adequate sperm count is used for insemination
- sexual stimulation should continue for several minutes after semen enters the sow's reproductive tract. This ensures that the uterus actively forces the sperm towards the oviducts where fertilisation of the eggs occurs. The catheter is left in place to assist with stimulation.
Stimulation is important in the sow because the sperm have to travel 1-1.5m in the uterine horns. When removing the catheter, ensure that the free end is higher than the vulva or semen may siphon out. Allow the sow to remain undisturbed following insemination.
PCAI method
The alternative system is the post cervical (PCAI) or intra uterine insemination method that introduces the semen into the uterine body, close to the uterine horn and fertilization site. The method has proved very successful with multiparous sows. However, results when inseminating gilts have been variable and in many herds a gilt specific catheter is used to improve success rates.
The PCAI method uses a foam tipped rod (catheter). Inside the rod is a second catheter or sleeve which is pushed through the rod and beyond the sow’s cervix. The sleeve threads through the cervix and deposits the semen directly into the uterine body. The success of PCAI relies on the cervix being totally relaxed as the semen is squeezed into the uterus. Boar stimulation during insemination does not encourage the cervix to relax and is not required.
The PCAI method reduces waste and leakage of semen and diluent compared with the cervix insertion method. A smaller volume of semen can be used in the PCAI method and the procedure is faster than the long establish CAI method. The cost of catheters for the PCAI method is higher than for the more popular CAI method.
When using the PCAI method:
- the sow must be well stimulated prior to PCAI by contact with a mature boar through a pen division
- remove boar and wait for the 30 minutes for sow to relax before attempting to inseminate
- clean the vulva with a paper towel to avoid drawing particles and micro-organisms into the female genital tract during insemination
- discard the paper towel after each action
- wait 1–2 minutes for cervix to relax before inserting rod (cannula)
- introduce the semen—there should be no reflux with PCAI
- gently squeeze the semen bag to accelerate movement of semen through uterine tract
- it might be necessary to use different size rods for gilts and mature sows.
Inserting the catheter
Before inserting the catheter:
- clean the sow's vulva and the area around it with a fresh, damp cloth or paper towel. This reduces the chances of introducing infectious material into the uterus and provides sexual stimulation
- discard the soiled cloth or paper towel after each action.
- manually stimulate the sow in the presence of a mature boar to induce the mating stance. This is done by applying pressure between her shoulder and midback, applying knee pressure to her flanks and massaging her vulva and udder.
Lubricate the tip of the catheter (Melrose type only) with a small amount of semen. Part the lips of the vulva and gently insert the catheter upwards into the vagina, ensuring that the tip does not penetrate the urethra (the bladder opening on the vaginal floor). Accidental penetration of the urethra allows urine to flow from a distended bladder through the catheter (urine harms sperm, so a fresh catheter should be used).
Gently push the catheter through the vagina until resistance is felt at the opening of the cervix. Rotate spiral-tipped catheters anti-clockwise and steadily push to lock into the cervix. The funnel-shaped cervix of a sow in oestrus is firm and well lubricated, so the trained staff member can apply positive pressure while locking in the catheter. The shape of the cervix helps to direct the catheter so insertion is seldom difficult (in some gilts the hymen membrane may cause resistance in the first 10cm).
Insert the catheter as far as it will go. The flange on the non-spiral catheter should be felt passing over the cervical folds. This type of catheter locks in when a gentle pull fails to free it.
When using the PCAI method the onset of oestrus is identified by contact with a mature “spotter” boar through a pen division. The optimum time for insemination is confirmed by the sow’s interaction with the spotter boar. Insemination of the sow commences 30 minutes after the spotter boar is removed. The PCAI method of insemination requires a foam tipped rod with an internal rubber sleeve. The rod locks into the cervix like any foam tipped catheter. The internal sleeve threads through the cervix and deposits semen directly into the uterus.
The critical step with the PCAI method is to allow time for the cervix to relax before attaching the semen bag which on large units could hold multiple doses. Allowing the cervix to relax makes it easier for the sleeve to negotiate the cervix. After attachment, the semen bag is squeezed to initiate the flow of semen into the uterus. The sow should remain calm during insemination and boar stimulation is not recommended and should be avoided.
Attaching the semen bottle
Spermatozoa lose their motility and settle to the bottom of the bottle when semen samples are stored within the appropriate temperature range (15–20°C). The bottles or tubes must be gently agitated or turned twice a day and before use to re-suspend the sperm.
Remove the chilled semen bottle from its pack and allow the semen to warm up 30 minutes before use (this can be done by placing the bottle in a warm place). Gently rock the insemination bottle to redistribute the spermatozoa immediately before use.
Cut the tip of the inseminating bottle with a clean, sharp knife. Grip the bottle by its cap and firmly fit the tip into the inserted catheter. Raise the bottle over the sow’s back and squeeze it a little to remove the airlock in the catheter. With the aid of gravity, semen is drawn into the sow by wavelike muscular contractions in her uterine horns. Continue sexual stimulation to promote contractions.
When using PCAI the semen bottle is squeezed to encourage flow of semen to the uterus. The sow should be calm with no sexual stimulation to encourage contractions as in the CAI method of insemination.
Common issues when using the CAI method
If semen does not flow freely from a soft-walled inseminating bottle or when gentle pressure is applied to a less pliable one, the following problems may occur:
- Opening at the catheter's tip may be blocked by a fold in the cervix – withdraw the catheter a little or slightly rotate the spiral tipped catheter.
- Sow may not be content or sufficiently stimulated – as the hormone oxytocin is responsible for uterine contractions during insemination. Aggressive handling, especially for nervous sows, triggers the release of adrenaline, a hormone that inhibits oxytocin. Boar presence, firm hand rubbing between the sow's shoulder and midback area, knee pressure in the flank and massaging the vulva and udder stimulate the sow. Periodic movement of the catheter also helps.
- There may be a blockage in the bottle –- if resistance is felt when the bottle is firmly squeezed. Remove the bottle and if necessary, the catheter, to check for a blockage. Gel particles, faulty equipment or a small opening in the semen bottle spout may cause blockages.
Common issues when using the PCAI method
- The cervix is not relaxed and semen rushes back into the semen bag—the sow needs to be calm for PCAI method.
- When semen rushes back into the bag, wait 1–2 minutes for the cervix to relax and try again.
© The State of Queensland 1995–2024
- Last reviewed: 08 Sep 2021
- Last updated: 08 Sep 2021