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Pregnancy Toxaemia
Grass Tetany

Pregnancy toxaemia (twin lamb disease)

Pregnancy toxaemia strikes ewes carrying twins or one large lamb, usually in the last few weeks before lambing. It is caused by negative energy balance, as the ewe is unable to supply enough energy to meet her own demands as well as those of the fast-growing foetuses. The incidence of the disease may typically range between 1-5% of single-bearing ewes and 10% or more of twin-bearing ewes.

Energy requirements of a ewe in the end stages of pregnancy are double that of a non-pregnant ewe, while twin-bearing ewes need 2.5 to 3 times the energy needed to prevent a non-pregnant ewe lose weight. If sufficient energy is not supplied (by pasture or supplements) the first consequence will be reduced birthweight of the lamb, then breakdown of the ewe’s body reserves. If this is accompanied by bad weather or other stressors, the ewe will go into energy deficit and suffer depression, then lie down and die within 2 to 7 days.


Oral solutions for pregnancy toxemia.  These contain propylene glycol and are administered like a high-volume drench. e.g. Vytrate 160 mL of undiluted concentrate every 4-6 hours. Injectable solutions are also available. Response to treatment is usually slow, particularly if the ewe’s condition is advanced. Offer good quality hay and oats to the affected ewe if she is able to eat. If ewes do not respond to treatment within 12 hours, they should be humanely euthanised.

Pregnancy toxaemia can be prevented by:

Checking ewe body condition in mid pregnancy and not allowing them to become ‘overfat’ i.e. try to keep average BCS below 4

Ultrasound pregnancy testing all ewes and separating empties, singles and twin-bearing ewes

Giving twin-bearing, older ewes and early-lambing ewes supplementary feed, especially in the final six weeks prior to lambing
Avoiding all management procedures that involve tipping sheep up (e.g. crutching, shearing, foot-paring) in the six weeks prior to lambing, and other procedures (drafting, drenching, vaccination) in the two weeks prior to lambing

Avoiding all procedures (mustering, yarding etc.) that prevent ewes from feeding for more than 12 hours

Monitoring weather conditions and providing ewes with supplemental feed (e.g. palatable hay) in times of cold or wind

Hypocalcemia (milk fever)

Milk fever is associated with pregnancy in sheep. Despite the name "milk fever" the disease does not result in any raised temperature (fever) or infection. The disease occurs when insufficient calcium is absorbed by the digestive system or from the bone tissue, to provide for the growing lamb in the uterus. If the blood calcium levels continue to drop significantly, the muscles cease to contract properly and paralysis sets in. Cereal pastures in winter are often high in phosphate, which makes it difficult for ewes to ingest sufficient calcium and magnesium.

High risk animals:

Older ewes

Ewes in the last few weeks of pregnancy

Animals held off feed for more than 18 hours or in grazed out paddocks

Animals unable to feed due to cold, wet weather or due to management activities


Inability to walk

Nervous signs

Lying down on their sternum

Dilated pupils


Death can occur within 1-2 days of collapse



See your vet to determine the best treatment for your animal. An injectable product containing calcium borogluconate is a common solution to increase tissue calcium levels. Always follow the label when administering these products. Recovery is usually rapid (30 minutes or so) and the rapid response can be regarded as diagnosis of the condition. Treatment can be repeated every 4–6 hours for animals that do not make a full recovery.


Hypocalcemia can be prevented by supplementation of ewes with calcium provided in the form of lick blocks, or crushed limestone.

If your flock is fed grain or on a cereal crop, the provision of 1.5% calcium carbonate and salt in a lick will help to increase calcium levels.

Also take care not to hold ewes (especially in the last 60 days of pregnancy) off feed for longer than is absolutely necessary.

Metabolic Diseases

Grass tetany (grass staggers)

Winter pastures are often low in legumes and therefore calcium and magnesium-deficient. Sheep do not store magnesium in the body, so need to ingest it each day to ensure their daily needs are meet. Any situation that prevents sheep from eating (mustering, holding in shed before shearing, bad weather) can trigger grass tetany.


Low magnesium in the blood

It can occur both before and after lambing

Rapid changes in the diet to a high quality feed


Nervousness and slight shaking when disturbed

Walking with stiff legs, staggering and falling over when mustered

If the sheep goes down she will paddle with her legs and hold her head

If ewes are found dead in the paddock there may be signs of froth around the mouth

May also be seen in fast-growing lambs e.g. weaners that have been held in yards

Ask veterinarian to confirm diagnosis and advise the correct product and the way to give it. It may be necessary to consider milk fever, as outbreaks sometimes involve both diseases.


Dust paddocks with calcined magnesite before grazing if you expect major problems

Wear a mask when applying the dust

Check the soil tests to see if potassium levels are excessively high as this can be a predisposing factor


Provide Causmag in a lick with salt and lime (crushed limestone)

Further Reading

A Better Way To Buy