Problems of the Periparturient Ewe
Lambing time is always the busiest time of the year for those vets who do any sheep work. The problems occur from pre-lambing, through lambing and into the post-lambing period. A lot of the problems are related to nutrition, and therefore good management in this area can dramatically reduce problems.
|main causes of ewe losses|
Immediate postpartum losses
This is a common, potentially fatal, but preventable disease of ewes that normally occurs in the last few weeks of pregnancy when the ewe requires more energy than she is receiving. Factors that can lead to this condition include:
Several animals are normally affected over a few days. Affected animals will separate from the flock, appear depressed, inappetent (standing at feed troughs with the other ewes, but not eating) and sometimes seek water without drinking. They sometimes turn in circles or become blind (typically with a loss of menace response, but not pupillary light response) and some will be twitching, salivating and fitting which will progress, if untreated, to convulsions, recumbency and death within two to three days.
Treatment involves drenching with keto-glycol and nursing. If the ewe is very heavily pregnant and shows no sign of improvement it may be necessary to induce her to remove the pressure of the lambs' energy demands. Nutrition is critical to prevention and on farms where problems have occurred before, the only option is to give this area attention early in the year, at weaning time, to ensure the ewes are in the right condition score and not over fat. Nearer to lambing the condition and foetal load of the ewes must be considered to ensure feeding is appropriate.
is considered the most common metabolic disorder seen in ewes. The calcium requirements of a ewe depend on age, growth and reproductive stage. Calcium deficiency is often seen in the periparturient period, at any time from several weeks pre-lambing to 4-6 weeks after. As well as the clinical signs described below, occurances during lambing can have an effect on parturition, stopping the cervix from fully dilating. It can be precipitated by poor or imbalanced nutrition and external stressors. It is often referred to as ‘staggers’ by farmers which can be confusing as many of us are more used to this referring to hypomagnesaemia in cattle. The disease often lasts hours rather than causing sudden death and progresses from incoordination to recumbency and finally coma. Animals respond rapidly to an injection of calcium borogluconate. Diagnosis is often made empirically in the field, observing the response to treatment but blood levels can be checked. Attention to diet, feeding plan and delivery, condition score, foetal load and avoiding unnecessary stress is critical to avoiding this condition.
Hypomagnesaemia... is seen less frequently than hypocalcaemia. It has similar signs but the disease occurs more acutely and sudden death can occur. It is almost always related to insufficient magnesium intake and so prevention involves correct nutrition. Boluses can be used to protect ewes on susceptible premises but the condition is reasonably rare.
The main causes of abortion (excluding metabolic causes) are Toxoplasmosis, Enzootic abortion, Campylobacter, Salmonella, and Border disease. Whilst the details of these would require an article alone to do them justice, their significance to the periparturient ewe is worth mentioning. One area which can receive insufficient attention at this busy time of the year is recording of ewe and lamb events on farm; the problem can be exacerbated by many farmers' reluctance to record what they view as the "failures" of the lambing season as they can make depressing reading! This can lead to a delay in reporting problems. The sooner an abortion problem is identified and diagnosed the earlier control measures can be implemented. The aim is to reduce losses and ensure the fewest number of ewes are affected. Education of the farmer is critical to get aborted ewes isolated as quickly as possible (including placentae and foetuses) to minimise spread and further losses. Diagnosis of the causal organism for the abortions is essential to allow future control and preventative measures to be put into place, and in the case of enzootic abortion to inform the decision to use oxytetracycline in the face of the outbreak. If possible, an aborted foetus with placenta including cotyledons, should be sent for testing. It is also critical to advise farmers and anybody else working on the farm or in contact with the sheep, of the potential risk from ovine abortion to pregnant females, and in some cases the zoonotic risks to all connected with lambing.
Prior to lambing ewes can show oedema of the perineum, which may progress to involve the udder and closely related abdomen. This can predispose the ewe to clostridial disease as the tissues become more fragile and liable to puncture or tear during lambing. Infection can occur and progress rapidly postpartum. Affected animals develop pyrexia and quickly deteriorate with accompanying subcutaneous emphysema. Ewes rarely recover. Diagnosis by post-mortem is useful but difficult as the presence of clostridial infection and associated toxins encourages decomposition. Vaccination is the only way to protect animals against clostridial diseases but it should be accompanied by good hygiene during lambing.
Vaginal and Uterine Prolapse
Vaginal prolapse occurs before lambing whilst uterine prolapse occurs less frequently afterwards, often as a result of parturition problems. Vaginal prolapse cases can range from relatively mild, where part of the vaginal wall appears at the vulva when the ewe lies down, to traumatic damage of the cervix and prolapse of the intestines through tears in the vaginal wall.
Vaginal prolapse... occurs in about 1% of ewes, although some flocks will report no incidences whilst in others the rate can be as high as 7%. Prolapsed ewes have increased risk of abortion, dystocia, stillbirth and neonatal mortality, and prolapse is a significant cause of ewe mortality.
Predisposing factors for vaginal prolapse include:
Prolapse requires veterinary treatment and the use of epidural anaesthesia to return the tissue and apply sutures or a harness to help prevent further prolapse before lambing. Both sutures and harness must be removed once the ewe begins labour to allow the lambs to be delivered. The harness is a preferred option as it is better for the welfare of the ewe and in our experience, possibly even more effective than sutures. Prevention will be related in most cases to corrective nutrition in future years.
Failure of the cervix to dilate is called "ringwomb." It is one of the most difficult lambing problems to deal with. Occuring most commnoly in ewe lambs, true ringwomb does not usually respond to any medical treatment or to manipulation of the cervix. A caesarean section is usually the only viable option, and ewes who have experienced ringwomb should probably be removed from the flock. Selenium deficiency is considered to be a contributing factor, but the condition is not fully understood and its exact cause is unknown, though it is believed to have a genetic component.
Post lambing trauma can be due to severe cases of foetal oversize, unskilled intervention or excessive interference by the farmer during lambing. The result could be either uterine, cervical, vaginal or vulval tears or trauma, involving the rectum and/or anus. Death may occur due to severe haemorrhage or from the development of metritis leading to peritonitis or a fatal prolapse of the intestine.
Bacteria inevitably enter the ewe's reproductive tract post lambing, and usually the ewe can mount a sufficient immune response to remove these invaders before they cause harm. However, if any of the above problems exist then the bacteria can colonise the tract and lead to toxaemia and metritis.
Metritis presents with at least some of the following clinical signs:
Treatment includes the use of antibiotics, oxytocin and an appropriate NSAID. The prognosis is usually good for affected ewes, with a rapid response to treatment.
This article was provided by The Sheep Veterinary Society, for more information including details of their meetings aimed at recent graduates visit www.sheepvetsoc.org.uk