Livestock health
Pregnancy toxaemia and hypocalcaemia

Dave Jordan, Agency for Food and Fibre Sciences

Key points

• Pregnancy toxaemia and hypocalcaemia are two metabolic diseases of ewes in the late stages of pregnancy.
• Pregnancy toxaemia is usually the most common of the two diseases, which in severe cases often causes high losses of ewes and lambs.
• These diseases often initially appear similar, can be triggered by similar factors, and can occur together.
• First indications that late-pregnant ewes are affected by one of these diseases are often seen during mustering or yarding for the pre-lambing shearing or crutching.
• These diseases are fatal if left untreated. To be effective, appropriate treatment must be given early.

The diseases in brief

Pregnancy toxaemia (lambing sickness or twin lamb disease)

Pregnancy toxaemia is a dietary deficiency of digestible energy, resulting from a significant decline in the level of nutrition in the last two months of pregnancy when 70 per cent of lamb growth is taking place. It particularly occurs in ewes that are carrying twins and which have previously been on a good plane of nutrition earlier in pregnancy. While the ewes may appear to be in good condition, their level of nutrition will usually be found to have fallen recently, e.g. due to pasture damage from rain or frost or the more nutritious components having been eaten out. Losses in Queensland ewe flocks from the combination of poor nutrition in late pregnancy and pregnancy toxaemia in ewes carrying twins and heavy single lambs have been as high as 25 to 30 % of ewes and a majority of the lambs.

Hypocalcaemia (milk fever)

Hypocalcaemia is caused by a calcium deficiency in the bloodstream. It may be predisposed by a deficiency of calcium in the diet (e.g. ewes feeding on poor quality pastures or grain diets without added calcium) or by grazing oxalate-containing plants that bind calcium in the intestines, preventing absorption. Hypocalcaemia is most often seen in the last six weeks of pregnancy and the first three months of lactation when the ewe is providing calcium for lamb bone development and milk production.

Precipitating factors

While ewes in late pregnancy can tolerate quite low levels of energy and calcium whilst grazing undisturbed in the paddock, a number of factors can place extra stress and nutritional demands on the ewes and precipitate the onset of these diseases. These factors in late-pregnant ewes include:

• mustering for shearing or crutching;
• holding off-feed for long periods such as in the yards for shearing or crutching, or while trucking;
• severe cold, rain or wind cause ewes to seek shelter rather than graze and the extra muscular contractions required for shivering and maintenance of body heat exhaust low energy reserves; or
• sudden change of diet, e.g. onto lush pastures resulting in dietary upsets or being held in eaten-out holding paddocks.

Initial indicators of these diseases

Often the first indications that heavily pregnant ewes are affected by one of these conditions may be seen during mustering or yarding for the pre-lambing shearing or crutching. Ewes start lagging back on muster, are disinclined to move and appear to stagger. Closer examination of these ewes, their recent history and the signs they are exhibiting is necessary to determine the appropriate diagnosis and allow early treatment while it can potentially be effective.

Typical signs and indications that differentiate these diseases

Pregnancy toxaemia	Hypocalcaemia
Slow progression of the disease with death after 5-7 days	Rapid progression of the disease with death after 6-24 hours
Earliest signs include: Separation from the flock Apparent blindness with alert bearing but disinclination to move Standing still when approached Blundering into objects when forced to move and pressing the head into obstacles May stand in water all day lapping water.	Earliest signs include: Stilted proppy gait Muscle tremor, especially in the shoulder muscles Alert and struggles when approached Appears weak, staggers about and goes down. Once ewes go down, they tend to stay down unless effective treatment is given.
In the later stages: Marked drowsiness Tremors and spasms of the head, face and neck muscles with the head pulled back or sideways Abnormal postures, elevation of the chin ('star-gazing'), muscle tremors on legs, incoordination, falling and convulsions There may be a thick, often yellowish and candlewax-like discharge from the nose. Recumbency: Slow progression to recumbency 2-3 days after onset of initial signs Profound depression or coma until death 2-6 days after onset of signs.	Recumbency (lying down): Rapid progression to recumbency over 3-4 hours Sternal recumbency with the head stretched out and chin on the ground with legs folded beneath or stretched out behind the ewe is usual. Watery discharge from nose may occur. Vaginal prolapse may occur. Drowsy appearance rapidly gives way to severe depression and coma. Death is usually rapid, within 6-24 hours without treatment. Some cases may linger for up to 3 days.
Post-mortem findings: Liver is yellowish with a fine mottled appearance characteristic of pregnancy toxaemia. Abdominal fat shows white flaky or chalky patches indicative of fat breakdown.	Post-mortem findings: There are usually no significant and characteristic observable post-mortem findings.
Response to treatment: No response to hypocalcaemia treatment dose rates of commercial calcium solutions. Varied (but usually poor and slow) response to doses of glucose or energy, with best responses seen if treated whilst ewes are still alert.	Response to treatment: Rapid and good recovery after injection of treatment doses of commercial calcium solutions, even in the later stages. Signs of recovery seen from within a few minutes to about half an hour of the injection.

When there is a rapid progression of the above signs associated with pregnancy toxaemia, with rapid collapse and death with or without convulsions, hypocalcaemia is usually also involved.

Under more intensive sheep-raising conditions, these diseases are a lot easier to tell apart because the sheep are observed more often and for longer periods so that the earlier signs can be more easily differentiated.

If these signs are seen during mustering, do not force affected ewes to continue. Retrieve them in a vehicle, hold them in the yards or small holding paddock and treat as necessary.

Pregnancy toxaemia

Treatment

If ewes are treated appropriately soon after the earliest signs are seen and while they are still reasonably alert, they are more likely to recover. Treatment once ewes have become drowsy produces poor responses.

An energy solution (e.g. molasses) or a glucose¹ or propylene glycol² drench can be given, followed by a subcutaneous injection of a commercial calcium solution³ (with added glucose). Dose according to the instructions on the label. Follow-up treatments may be necessary. The injections are not recommended as the sole treatment as relapses often occur, however they have the advantage of treating any hypocalcaemia that may also be present.

Drenching with up to 1 litre of water may be necessary to overcome dehydration. Accessible water and shade and the provision of adequate soft feed such as grain or lucerne hay is necessary to keep the digestive system working and supplying energy.

Subcutaneous injections of commercial calcium mixtures should be administered under the skin of the neck, shoulder or over the ribs. The injection site can be massaged to help distribute the solution. Larger doses should be administered over more than one injection site. If you suspect that your ewes may be susceptible to pregnancy toxaemia, be prepared and have a preparation of these treatments on hand. They are readily available from your local agent or veterinarian.

Once ewes start exhibiting signs of pregnancy toxaemia, energy supplements should be provided to the mob as soon as possible to minimise the chance of further cases.

Prevention

Prevention of pregnancy toxaemia is far better than trying to cure it. You can avoid pregnancy toxaemia by recognising and anticipating the decline in the level of nutrition in the pasture, and providing better pastures or energy and protein supplements to meet the increased nutritional requirements of pregnant ewes and the extra requirements for pre-lambing management.

To ensure that ewes take to the supplement in time to improve their energy status before any mustering, shearing, crutching or lambing, feed energy supplements for two to three weeks before the anticipated event. If necessary, continue the feeding during shearing or crutching. Where possible only hold the first run of heavily pregnant ewes in the yards overnight when shearing or crutching and minimise the time they are in the yards.

Hypocalcaemia

Treatment

Affected sheep will respond quickly to an injection of a commercial calcium solution. However, hypocalcaemia may also be accompanied by pregnancy toxaemia, therefore commercial calcium solutions³ (with added glucose, magnesium and phosphorus) are the ideal medication to keep on hand for both conditions. These include Calcigol Plus and Flopak Plus (4 in 1) that are readily available from your local agent. Dose according to the instructions on the label. To be prepared, and help minimise losses, ensure you have one of these commercial preparations on hand.

Prevention

Preventative measures include minimising stress to ewes that are heavy in lamb, providing a well-balanced diet and avoiding placing hungry stock and/or pregnant ewes in paddocks heavily infested with plants containing oxalate. When supplementing with grains, which are low in calcium, the inclusion of 1.5% finely ground limestone (calcium carbonate) supplements these low levels. Where possible only hold the first run of heavily pregnant ewes in the yards overnight when shearing or crutching and minimise the time they are in the yards. Provide supplementary feed if necessary.

Further information

For further information contact the DPI Customer Service Centre on 13 25 23 (Queensland residents) or (07) 3404 6999 (non-Queensland residents) between 8 am and 6 pm weekdays, or e-mail callweb@dpi.qld.gov.au

This DPI Note is also published on the DPI's PrimeNotes CD-ROM.

¹ Vy-trate is a commercial glucose drench.

² Keton, Ceton and Protocol are commercial propylene glycol drenches.

³ Calcigol Plus, Flopak Plus, Glucalphos and Unical Four are commercial preparations.

---

Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.

---

File No: SW0107 . Date created: July 2002 . Reviewed: August 2003