Pregnancy toxaemia and hypocalcaemia of ewes

Pregnancy toxaemia and hypocalcaemia affect lambing ewe flocks and have similar signs but different causes. As pregnancy toxaemia and hypocalcaemia require different treatments it is important to be able to understand, recognise and prevent both of these diseases in lambing ewe flocks.

Both pregnancy toxaemia and hypocalcaemia can be avoided if producers provide adequate ewe nutrition and minimise herding and yarding of ewes in late pregnancy and early lactation.

Surveillance testing subsidised to support market access

Each year Australia requires eligible sheep brains to be tested as part of the National Transmissible Spongiform Encephalopathies Surveillance Program (NTSESP). This helps demonstrate that Australia is free from TSEs including scrapie in sheep, which is needed to maintain market access for Australia's livestock and livestock products.

 

If sheep show signs of pregnancy toxaemia or hypocalcaemia or any other neurological signs, contact your local Department of Agriculture and Food (DAFWA) veterinary officer or private veterinarian and ask them to check if the case is eligible for a department-subsidised veterinary investigation and an incentive payment.

 

Report unusual disease signs, high death rates or abnormal behaviour in stock — call your veterinarian or the local DAFWA Veterinary Officer or the Emergency Animal Disease hotline on 1800 675 888.

Differentiating between and preventing pregnancy toxaemia and hypocalcaemia are recurring issues for producers, particularly around the time of lambing.

Pregnancy toxaemia

What is pregnancy toxaemia (twin lamb disease)?

Pregnancy toxaemia occurs when drastically low levels of glucose in the blood damage the brain and result in dehydration, kidney failure and potentially death. It usually occurs in the last weeks of pregnancy with the ewes most advanced in pregnancy affected before the rest of the flock.

What causes pregnancy toxaemia?

Pregnancy toxaemia occurs when the pregnant ewe does not receive enough nutrition. In Western Australia, autumn is a precarious time for ewes because dry feed is minimal and the pregnant ewe’s nutritional needs are increasing, making her susceptible to pregnancy toxaemia.

Which sheep are most at risk of pregnancy toxaemia?

  • ewes in late pregnancy and ewes with twin lambs
  • early lambing flocks when there is a late break and stubbles/dry feed have deteriorated
  • ewes feeding on new green pasture high in water and low in dry matter and nutrients
  • ewes that stop eating during extreme weather.

What are the signs of pregnancy toxaemia?

  • ewe is separated from the mob
  • ewe is drowsy or comatose
  • ewe is not eating
  • nervous system signs – tremors, blindness
  • lying on their side for 3–4 days
  • death 3–4 days later.

How can a veterinarian help?

Early diagnosis of the disease and treatment are essential to prevent further progression. A veterinarian can perform several tests on a live animal to diagnose pregnancy toxaemia. A veterinarian may consider inducing the pregnant ewe to birth or performing a caesarean section.

How can I treat pregnancy toxaemia?

Consult with a veterinarian about the most effective treatment for your animals. A glucose drench or injectable glucose every 6–12 hours will provide a rapid increase in the ewe’s blood sugar levels. 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 euthanased.

How can I prevent pregnancy toxaemia?

Good nutrition and careful management are the keys to avoiding pregnancy toxaemia. Lambing ewes require feed on offer of more than 1500 kilograms per hectare during lambing. If this is not available, provide a supplementary source of energy, such as good quality hay and grain. However, avoid making sudden changes to their feed or causing short sudden periods of starvation such as during yarding.

If extreme weather conditions cause ewes to stop eating or become stressed, provide supplementary feed. Take care to avoid grain poisoning by introducing grain slowly.

It is recommended to identify twin mothers using pregnancy scanning and then to separate and preferentially feed them to minimise the development of pregnancy toxaemia.

Hypocalcaemia

What is hypocalcaemia (milk fever)?

Hypocalcaemia, also known as milk fever, is a deficiency of calcium in the bloodstream which causes muscles not to contract properly, including the heart, gut and leg muscles.

Which sheep are most at risk?

Ewes in their last six weeks of pregnancy and in the first month of lactation are most at risk as during this time the ewe is providing calcium for lamb bone development and milk production.

Unlike pregnancy toxaemia, hypocalcaemia is not confined to pregnant ewes. Prime lambs or other sheep in good condition that are stressed after moving, trucking or yarding are susceptible to hypocalcaemia. Sheep that stop eating during extreme weather conditions are also at risk of developing hypocalcaemia.

What causes hypocalcaemia?

Hypocalcaemia is caused by the animal being unable to mobilise calcium from the bone quickly enough to meet demand. Cases of hypocalcaemia can be associated with grazing cereal regrowth (low in calcium) and pastures with a high oxalate content. Oxalate combines with calcium in the bloodstream, effectively removing it from the system and causing hypocalcaemia.

Many of the weeds that form a significant part of the ewe diet over summer such as goosefoot or mintweed (Chenopodium pumilo), fat hen (Chenopodium album) and the various salt-tolerant succulent weeds from around salt pans have significant levels of oxalate. Other green season plants such as soursob (Oxalis spp) and to a lesser extent sorrel (Rumex conglomeratus), the docks (Rumex spp) and doublegee (Emex australis) also contain oxalate. Where pregnant ewes have been grazing on these plants, the risk of hypocalcaemia increases and ewes’ tolerance of other compounding stress factors such as yarding or transport reduces.

What are the signs of hypocalcaemia?

  • rapid onset
  • stiff uncoordinated gait
  • muscle trembling
  • weakness
  • a ewe sitting down on her brisket and unable to get up
  • death within 24 hours.

How can a veterinarian help?

A veterinarian can help by collecting blood for testing to determine the calcium levels in the animal. Few changes are seen on post-mortem. A veterinarian can treat affected sheep with a calcium supplement directly into the bloodstream of the sheep. Recovery is almost instant.

What is the treatment for hypocalcaemia?

A range of injectable products containing calcium borogluconate will 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.

How can I prevent hypocalcaemia?

Like pregnancy toxaemia, good nutrition and careful management are the keys to avoiding hypocalcaemia. Provide good quality hay and grain to stock about to lamb and avoid sudden changes in their feed or a short, sudden period of starvation such as yarding. Adding limestone to grain rations or supplementing with a loose lick which contains calcium can help prevent hypocalcaemia.

Surveillance testing subsidised to support market access

Each year Australia requires eligible sheep brains to be tested as part of the National Transmissible Spongiform Encephalopathies Surveillance Program (NTSESP). This helps demonstrate that Australia is free from TSEs including scrapie in sheep, which is needed to maintain market access for Australia's livestock and livestock products. If sheep show signs of pregnancy toxaemia or hypocalcaemia or any other neurological signs, contact your local Department of Agriculture and Food veterinary officer or private veterinarian and ask them to check if the case is eligible for a department-subsidised veterinary investigation and an incentive payment.

Report unusual disease signs, high death rates or abnormal behaviour in stock — call your veterinarian or the local DAFWA Veterinary Officer or the Emergency Animal Disease hotline on 1800 675 888.

Table 1 Diseases that look like pregnancy toxaemia and hypocalcaemia
Disease Signs of disease Comments
Scrapie

Behavioural changes, tremors, unable to walk properly, constant scratching and evidence of wool pulling

Scrapie is not present in Australia. If you see signs of scrapie in your sheep, contact your local veterinary officer or private veterinarian immediately. Ask if the case is eligible for a subsidy under the National Transmissible Spongiform Encephalopathies Surveillance Program (NTSESP).

Rabies

Lack of coordination and paralysis

Rabies is not present in Australia. It is caused by a lyssavirus. If you see signs in sheep, contact your local veterinary officer or private veterinarian immediately.

Cerebral abscess

Weakness and involuntary movements

There are many causes of cerebral abscess, including bacterial or fungal infections.

Acidosis

Downer sheep, bloated, weak, comatose, death

Occurs when animals consume large quantities of grain or pellets to which they are unaccustomed.

Table 2 Comparison between pregnancy toxaemia and hypocalcaemia
 

Pregnancy toxaemia

Hypocalcaemia

Causes

  • Low levels of glucose in the blood
  • Increasing metabolic demand of pregnancy
  • Nutrition not meeting demand
  • Pregnant ewes feeding predominantly on green pick are at increased risk
  • Can be associated with yarding or transport
  • Can occur following severe weather.
  • Low levels of calcium in the blood
  • Can be secondary to eating plants containing oxalates
  • Nutrition not meeting demand
  • Pregnant ewes feeding predominantly on green pick are at increased risk
  • Can be associated with yarding or transport
  • Can occur following severe weather.
Signs
  • Ewes separated from the mob
  • Drowsy or comatose
  • Stop eating
  • Nervous signs – tremors, blindness
  • Go down and lie on their side for 3–4 days
  • Death 3–4 days later.
  • Rapid onset
  • Often a number affected
  • Stiff, uncoordinated gait
  • Muscle trembling
  • Down ewe sitting on her brisket unable to get up
  • Death within 24 hours.
Post-mortem changes
  • Twin lambs often found
  • Yellow liver.
  • No significant findings.
Treatment
  • Glucose drench or injection
  • Response poor to variable.
  • Calcium borogluconate injection
  • Response good if treated early.

Prevention

  • Good nutrition and careful management
  • Provide good quality hay and grain to stock that are about to lamb
  • Avoid sudden periods of starvation such as yarding.
  • Good nutrition and careful management
  • Provide good quality hay and grain to stock that are about to lamb
  • Avoid sudden periods of starvation such as yarding
  • Add limestone to grain rations or supplement with a loose lick containing a source of calcium.

DAFWA Veterinary Officer contacts

DAFWA Field Veterinary Officers can provide more information about pregnancy toxaemia and hypocalcaemia of ewes. To find the contact details of your closest DAFWA Field Veterinary Officer, go to the Livestock Biosecurity program contacts page.

Contact information

Anna Erickson
+61 (0)8 9881 0211
Page last updated: Monday, 28 November 2016 - 12:55pm

Author

Anna Erickson