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Parturition - Farrowing

(305) To appreciate the intricacies of the farrowing process it is necessary to understand the anatomy of the pelvis and the reproductive tract at farrowing. As farrowing approaches the vulva becomes enlarged, together with the vagina that leads to the cervix or opening into the womb. A small lubricated hand and arm can be inserted into the vagina to just beyond the cervix without damage. The neck of the cervix opens into the two long horns of the womb that contain the piglets. (Fig.8-10). The umbilical cord of the piglet terminates at the placenta which is attached to the surface of the womb. Nutrients pass from the blood of the sow across the placenta and into the developing piglet. The placenta also extends around the piglet as a sac which contains fluids and waste materials, produced by the piglet during its growth. The placenta and the sac are referred to as the afterbirth.



How does farrowing start

This is an intriguing mechanism activated by the piglet once it reaches its final stage of maturity, at approximately 115 days after mating. The sequence of events is depicted in Fig.8-11. The piglet activates its pituitary and adrenal glands to produce corticosteroids. These hormones are then carried via its blood stream to the placenta. The placenta then produces prostaglandins which are circulated to the sow's ovary. As you will have seen earlier, the corpora lutea in the ovaries are responsible for the maintenance of pregnancy. Prostaglandins cause them to regress, thus terminating the pregnancy and allowing the hormones that initiate farrowing to commence.

Length of pregnancy

The mean length in the sow is between 114 - 115 days with a range from 111-120. Gilts tend to have a shorter pregnancy. The variation within the range is influenced by the herd, environment, breed, litter size (it tends to be shorter in larger litters and longer in smaller litters) and the time of year.

The farrowing process

This can be considered in three stages, the pre-farrowing period, the farrowing process and the immediate post-farrowing period when the afterbirth is expelled.

Stage 1 - The pre-farrowing period
The preparation for farrowing starts some 10 to 14 days prior to the actual date, with the development of the mammary glands and the swelling of the vulva. At the same time teat enlargement occurs and the veins supplying the udder stand out prominently. The impending signs of farrowing include a reduced appetite and restlessness, the sow standing up and lying down and if bedding is available chewing and moving this around in her mouth. If she is loose-housed on straw she will make a bed. Within 12 hours of actual delivery of piglets, milk is secreted into the mammary glands and with a gentle hand and finger massage it can be expressed from the teats. This is one of the most reliable signs of impending parturition. A slight mucous discharge may be seen on the lips of the vulva. If a small round pellet of faeces is seen in the mucous and the sow is distressed, farrowing has started and it is highly likely the first piglet is presented backwards. This small pellet is the meconium or first faeces coming from the rectum of the piglet inside. An internal examination is immediately required. The final part of stage 1 is the opening of the cervix to allow the pigs to be pushed out of the uterus, through the vagina and into the world.

Stage 2. The farrowing process
This can range from 3 to 8 hours and piglets are usually delivered every 10 to 20 minutes but there is a wide variation. Consult the sow and litter card to see if there have been any previous problems at farrowing. For example if a sow has had high stillbirth rates, monitor her more closely and take any necessary actions. There is often a gap between the first and second piglet of up to three quarters of an hour. The majority of pigs are born head first but there are more pigs presented backwards towards the end of the farrowing period. Immediately prior to the presentation of a pig the sow lays on her side, often shivering and lifting the upper back leg. This is an important point to take note of because it may indicate the presence of a stillborn pig. Twitching of the tail is seen just as a pig is about to be born.

Stage 3. Delivery of the placenta
This usually takes place over a period of one to four hours and is an indication that the sow has finished farrowing although some afterbirth will sometimes be passed during the process of farrowing. Once the sow has completed the farrowing process there are certain signs that should be observed.

  • She appears at peace, grunts and calls to the piglets.
  • The shivering and movement of the top hind leg ceases. If this is still occurring it is likely that a pig is still presented.
After the placenta has been delivered there will be a slight but sometimes heavy discharge for the next 3 to 5 days. Provided the udder is normal, the sow is normal and eating well ignore it, it is a natural post-farrowing process. Occasionally a pathogenic organism enters the uterus causing inflammation (endometritis). This may cause illness, requiring treatment.

What to do when there are farrowing problems

Step 1. Recognise that the sow is in difficulty. This is shown either by lack of piglets being born, the sow panting heavily and obviously in distress or blood and / or mucus at the vulva.

Failure to deliver the piglets can be due to the following:

  • A large litter and inertia of the womb.
  • Very large piglets and a small pelvis.
  • Two or more pigs presented in the birth canal at the same time.
  • Illness of the sow, for example acute mastitis.
  • Rotation of the womb.
  • Failure of the cervix to relax and open.
  • Dead pigs inside the womb.
  • Mummified pigs.
  • Failure of the womb to contract (uterine inertia).
  • Nervousness of the sow, excitement and distress.
  • An over fat sow.
Step 2. Investigate. Never carry out an internal examination without a container of clean warm water containing a mild antiseptic and use a soft soap or preferably a special obstetrical lubricant. Do not use detergents, they are irritant and never be tempted to try and force a dry arm into the vagina of the sow.

Step 3. Wash the hands and arm well and in particular ensure the finger nails are short. It is preferable to use a plastic arm sleeve because this reduces contamination from the hands.

Examine the sow as she is lying down on her side. It is easier to use your left hand if she is on her left hand side and your right hand if she is on her right side. Occasionally you may have to examine the sow in a standing position.

Hold the fingers of the hand together and introduce the arm into the vagina in an arc as shown in Fig.8-10. Progress to the cervix and beyond so that you can feel the entrance to each horn of the womb. To do this your arm will have to enter up to the armpit.

Problems at farrowing

Uterine inertia - This is where the womb has just stopped contracting. Usually there will be two or three pigs waiting just beyond the cervix. If they are in an anterior presented position place the hand over the head with the first and second fingers around the nape of the neck. If the piglet is presented in a breech or backward position raise both hind legs and clamp the hands around using the first and second fingers as leverage around the points of the hock.

Difficult presentations - Occasionally (particularly in gilts) a large piglet is presented that is too big, but in most cases with gentle traction such a pig can be delivered. The best method is to use a piece of cord, 2 metres long (clean disinfected nylon cord is satisfactory) and loop the centre of it around the end of the third finger. Using plenty of lubricant pass the cord into the vagina to approximately 50mm behind the head of the piglet. The cord is then placed behind the left and right ears and finally brought down beneath the jaw. Twisting it lightly under the piglets chin may help to secure it. Traction can then be applied in a downward movement to bring the pig out. This is an excellent and simple technique and I would recommend that you familiarise yourself with it by cutting off the end of a wellington boot, place a dead piglet inside with its head presented to you and practice placing the cord around the neck.

Rotation of the horns of the womb - This sometimes occurs when very large litters are present. One horn crosses over the other. This distorts the cervix so that piglets cannot be pushed through and 2, 3 or 4 pigs form into a pouch below the cervix itself (many are presented backwards). When the hand is passed through the cervix (which has become elliptical) the pigs can be felt by reaching downwards and back towards yourself. In such cases it is necessary to take the arm full length into the sow (sow standing) and work hard to bring three or four piglets up. Once the piglets have been removed with the sow standing use a closed hand on the side of the abdomen, swing it to try and realign the piglets and horns of the uterus. If the sow has not passed further piglets within half an hour re-examine.

Stimulating a piglet to breath - If a piglet is delivered and it fails to breath take a small piece of straw and poke it up the nose. This will in many cases elicit a coughing reflex and remove mucus that has blocked the windpipe. Alternatively place the third finger across the mouth of the piglet with its tongue pulled forward. Place the rest of the hand around the head and hold the back legs. Swing the pig with a firm downward movement to propel any mucous from the back of the throat and the windpipe. (

Step 4. If after a manual examination you suspect some degree of uterine inertia, (through fatigue or some other reason the uterus has stopped contracting strongly) or the sow appears to have given up trying, a small injection of oxytocin (0.5ml) may be given. Normally it is not necessary because the pressure of the arm in the vagina stimulates further contractions. Well grown piglets passing through the vagina have the same effect but small mummified piglets do not, hence a stillborn piglet may follow after a mummified piglet. Piglets suckling the sow's teats also stimulate uterine contractions so gentle massage of the udder and teats with your hand may be helpful.

Step 5. If an internal examination has been necessary and the farrowing process has been completed an injection of antibiotic should be given . A injection of long-acting penicillin (10-15ml) should be adequate to prevent any potential infection.

If there have been dead possibly infected piglets present two antibiotic pessaries should be deposited through the cervix at the end of the third stage.

Step 6. Always monitor the sow frequently over the next 24 hours to make sure that infection is not developing in the udder or womb, that the placenta has been expelled and the sow is suckling her litter normally.

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