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.
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.
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.