Age affected: Gilts, sows.
Causes: Stress; large litter; crate too confined; mismanagement of farrowing; lack of exercise; dietary factors.
Effects: >30 minutes delay between births, stillbirths, MMA.
Uterine inertia (in which the uterus is no longer capable of expelling the piglets) may occur due to exhaustion when there is physical blockage of the cervix (exit from the uterus) by the presence of dead pigs or mummies, a piglet which is oversized, abnormally presented or malformed or by two piglets coming at once. It also occurs when there are large litters, in fat sows or as a result of illness in the sow. Illness in the sow can include infectious conditions such as erysipelas and non-infectious conditions such as heart failure and low blood calcium (hypocalcaemia). Uterine inertia may result in retention of one or more piglets and placentas.
Mode of transmission
Uterine inertia is not transmissible, but may occur following transmissible illness.
Uterine inertia shows as lack of progress with farrowing. In some cases the sow may be distressed or show signs of illness. If no piglets have been born, there may be mucus at the vulva and where they are in respiratory distress at the cervix, foetal faecal pellets (meconium) may also be present. 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.
When the cervix is open and some piglets have been delivered prior to the development of uterine inertia, 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. Where heart failure is present, the sow is dull, has a subnormal rectal temperature, congestion (purple colour) of the extremities, abnormal heartbeat and may die. Where hypocalcaemia is present, the sow becomes distressed, pants heavily and trembles. 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.
A delay of more than one hour since the last piglet was born or over 2 hours since straining began suggests that blockage of the cervix or uterine inertia may be present. The actual cause of the delay 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 with soap and water and with a mild disinfectant.
The hands should be washed and disinfected and inserted to establish the cause of the problem. The presence or absence of an open cervix can be determined and the nature of any blockage identified. Uterine inertia due to infectious disease may be identified by the clinical signs of the disease e.g. erysipelas. Non-infectious disease such as heart failure may be identified by congestion of the extremities confirmed by auscultation (listening to the heart with a stethoscope) and hypocalcaemia by noting the clinical signs of distress, panting and tremor. Confirmation is by giving intravenous calcium which restores the sow to normal.
Affected sows may die soon after uterine inertia occurs, even when the piglets responsible have been removed, or die some time later as a result of putrefaction of the uterine contents, particularly when the cervix is open. The carcass is usually congested and the abdomen is often distended. As would be expected, the udder is swollen and full of milk. There may be visible evidence at the vulva of the internal problems, with discharge or membranes protruding.
Prolapse of the vagina or rectum may be seen, but these may have occurred post-mortem due to increased intraabdominal pressure. On opening the abdomen, the uterus is distended and the outlines of any remaining piglets may be present. If putrefaction has begun, the whole uterus may be brownish or blackish. On opening the uterus, any piglets present will be visible and they any oversized piglets or those stuck at the cervix will be immediately obvious. The state of the cervix can be best seen by opening the pelvic cavity and then opening the vagina to expose the cervix. The distended uterus may have caused a rise in intra-abdominal pressure sufficient to push the diaphragm forward in the chest, reducing the lung area.
Treatment and prevention
Treatment of uterine inertia depends upon the cause. Illness in the sow should be treated where possible. Administration of cardiac stimulants may improve cardiac failure and intravenous administration of calcium borogluconate will restore sows with hypocalcaemia to normal. 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 0.5 ml 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. Piglets of sick sows should be fostered or supported.
When the sow is of particular value, and in companion animals, caesarean section can be carried out, but it may not save the life of the sow and piglets, and support for the latter must be made available. If it is clear that successful treatment is unlikely, the sow should be killed humanely.