Age affected: Gilts, sows.
Causes: Uterine inertia; large foetus; small gilt; mismanagement of farrowing.
Effects: No birth after >1 hour straining, >30 minutes delay between births, stillbirths, MMA.
Prolonged Farrowing (Dystokia)
Farrowing takes place between 111 and 115 days after service, takes 3-8 hours and is followed by a period of 1-4 hours when the placentas (afterbirths) are expelled. Piglets are delivered approximately every 15 minutes. Failure to begin farrowing by 115 days after all the behavioural steps have occurred can be because the cervix has not opened, there is torsion (twisting) of the uterus, physical blockage of the cervix (exit from the uterus) by a piglet which is dead, oversize, abnormally presented or malformed or illness of the sow resulting in uterine inertia.
Nervous sows may not begin farrowing when expected. After farrowing has started, piglets may take longer to appear or farrowing may be prolonged by the presence of dead pigs or mummies, physical blockage of the cervix by a piglet which is oversized, abnormally presented or malformed or by two piglets coming at once. Uterine inertia (in which the uterus is no longer capable of expelling the piglets) may then occur due to exhaustion, when there are large litters, in fat sows or as a result of illness in the sow. Uterine inertia may result in retention of one or more piglets and placentas.
The condition is not transmissible. When illness of the sow occurs, the illness itself may be transmissible. Prolonged farrowing is not an inevitable consequence.
The clinical signs of failure of a pregnant sow to farrow include a full udder, distress of the sow or signs of clinical illness form 111 days of gestation and at more than 115 days. When the cervix is open but piglets are stuck, the distressed sow may have mucus at the vulva. Where piglets are in respiratory distress at the cervix, foetal faecal pellets (meconium) may also be present. Foetal heartbeat can be heard using doppler equipment or a stethoscope and live piglets can be visualised by ultrasound.
If the sow is left untreated at this stage, the piglets die, infection may result and the sow becomes progressively more dull, fevered, congested and dies. Where the cervix opens, a thin reddish-brown offensive discharge may be produced. When the cervix is open and farrowing is interrupted or uterine inertia has occurred, piglets can be felt in the uterus close to the cervix by vaginal examination. In some cases, blockage may be detected and malpresented or oversized piglets felt. At the end of farrowing, the sow does not lie quietly until all piglets or placental material has been passed. Retained piglets or placental material often cause fever, bloody discharge, inappetence and agalactia.
Failure to start farrowing should be suspected when all of the signs which occur prior to farrowing are present and farrowing does not take place within 12 hours of the udder filling with milk and the vulva relaxing; or when farrowing does not take place by 115 days of gestation. When farrowing has started, delays of more than two hours since the last piglet suggest problems which indicate that prolonged farrowing is taking place. Prolonged farrowing is confirmed 8 hours after farrowing begins. The actual cause of the lengthened farrowing process must be established.
Unless ultrasound is available to identify the cause of the problem, manual examination through the vagina must be carried out. The vulva and adjacent perineum must be washed with soap and water and with a mild disinfectant. The hands should be washed and disinfected and inserted to establish the case of the problem. The presence or absence of an open cervix can be determined and the nature of any blockage identified. When the sow has not finished farrowing or when placentas have not been passed, then manual investigation through the open cervix is still possible for another 24 hours before closure of the cervix.
Sows which die during prolonged farrowing may be congested, have an engorged udder and a slack vulva. The actual cause of death may be toxaemia or heart failure. The heart may be grossly enlarged when valvular endocarditis is present.
Examination of the reproductive tract usually reveals a physical reason for the prolonged farrowing. There may be a dead or decomposing piglet stuck in the cervix or the whole uterus and its contents may be decomposing or there may be a uterine torsion. In sows which die during farrowing and which are examined while freshly dead, haemorrhages may be seen on the peritoneal surfaces of the abdominal organs and on the heart.
Treatment of prolonged farrowing depends upon the cause. Illness in the sow should be treated. When manual examination after washing and disinfection reveals an open cervix, deliver any piglets or placentas within reach. Manipulate jammed piglets into position for delivery and remove them. The interference should result in oxytocin release sufficient to stimulate the uterus to deliver further piglets and placentas without any additional treatment. Stimulation is enhanced if piglets already born are encouraged to suck or if the udder is massaged gently.
Where uterine inertia is confirmed and no piglets are presented or when mummies are being delivered, then 0.5ml of oxytocin should be given to stimulate contraction. The insertion of hands for any reason should be followed by injection of antimicrobial, such as penicillin and streptomycin or tetracycline to reduce the possibility of infection.
When the cervix is closed, where uterine torsion is suspected or where a blockage cannot be moved, the animals must be slaughtered or a caesarean section carried out by the veterinary surgeon. This may result in the delivery of live pigs, the correction of torsion or the piglets may be dead. Sectioned sows may develop agalactia and both sow and litter must be supported.