Background
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.
Differentiating between and preventing pregnancy toxaemia and hypocalcaemia are recurring issues for producers, particularly around the time of lambing. Both diseases can be prevented by close attention and suitable management of nutrition and husbandry in late pregnancy and lactation.
Pregnancy toxaemia
Pregnancy toxaemia, also known as 'twin lamb disease' occurs when glucose levels in the blood fall dangerously low.
The disease can damage the brain and result in dehydration, kidney failure and potentially death. It usually occurs in the last weeks of pregnancy, particularly in ewes more advanced in pregnancy, or carrying twins.
Pregnancy toxaemia occurs when the pregnant ewe does not receive enough good quality nutrition.
In Western Australia, autumn is a particularly precarious time for ewes because dry feed is minimal and of poor quality at the time the pregnant ewe’s nutritional needs are increasing, making her susceptible to pregnancy toxaemia.
Pregnancy toxaemia is more likely to occur in:
- ewes in late pregnancy, especially 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 that is high in water and low in dry matter and nutrients
- ewes that stop eating during extreme weather or ewes that are yarded for a period off feed.
Ewes experiencing pregnancy toxaemia may show the following signs:
- separation from the mob
- drowsy or comatose: indifferent to the approach of a person or dog
- loss of appetite
- nervous system signs, including tremors or blindness
- lying on their side for 3–4 days
- death occurring 3–4 days later.
Early diagnosis of the disease and treatment are essential to improve the chances of survival. A vet can perform several tests on a live animal to diagnose pregnancy toxaemia. A vet may consider inducing birth in the pregnant ewe or performing a caesarean section.
Consult with a vet about the most effective treatment for your animals.
Treatment includes:
- a glucose drench or injectable glucose every 6–12 hours to rapidly increase the ewe’s blood sugar levels.
- offering good quality hay and oats if the ewe is able to eat.
If ewes do not respond to treatment within 12 hours, they should be humanely euthanised.
- Good nutrition and careful management are the most effective prevention measures for pregnancy toxaemia.
- Lambing ewes may require more than 1,500 kg/ha dry matter during lambing. If this is not available, provide a supplementary source of energy, such as good quality hay and grain.
- Avoid making sudden feed changes 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.
- Introduce grain slowly to prevent grain poisoning.
- Pregnancy scanning is recommended to identify twin bearing ewes to then be separated and preferentially fed to minimise the development of pregnancy toxaemia.
- See DPIRD’s livestock calculators, including the supplementary feeding calculator for pregnant and lactating ewes for recommended supplementary feeding rates.
Hypocalcaemia
Hypocalcaemia, also known as 'milk fever', is a condition caused by low calcium levels in the bloodstream which causes muscles not to contract properly, including the heart, gut and leg muscles.
Ewes in their last 6 weeks of pregnancy and in the first month of lactation are most at risk. 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.
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 which is 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.
- rapid onset
- stiff uncoordinated gait
- muscle trembling
- weakness
- sitting down on the brisket and unable to get up
- death within 24 hours.
A vet can help by treating affected sheep with a calcium supplement directly into the bloodstream. Recovery is often almost instant and provides a diagnosis.
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).
- Treatment can be repeated every 4–6 hours for animals that do not make a full recovery.
If ewes do not respond to treatment within 24 hours, they should be humanely euthanased.
Like pregnancy toxaemia, prevention relies on good nutrition and careful management. Prevention measures include:
- providing good quality hay and grain to stock about to lamb
- avoiding sudden changes in feed or a short, sudden period of starvation such as yarding
- adding 2% limestone to grain rations
- supplementing with a loose lick which contains calcium.
| 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 DPIRD vet 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 abcess, 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. |
| Disease | Pregnancy toxaemia | Hypocalcaemia |
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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 unexplained neurological signs, contact your local DPIRD vet or private vet and ask them to check if the case is eligible for a department-subsidised veterinary investigation and an incentive payment.
Early detection of exotic disease
Producers play a vital role in the early detection of exotic diseases in Australia.
If you see any of the following in your stock:
- unusual disease signs
- abnormal behaviour
- unexpected deaths.
contact your private veterinarian, the local DPIRD vet or the Emergency Animal Disease hotline on 1800 675 888.
Early recognition and reporting of an exotic disease helps minimise the spread and enables economic containment if present. Veterinary investigations that confirm a suspect exotic disease is not present also provides supporting evidence of freedom from market sensitive diseases. This evidence enables Australian livestock and livestock products to enter important international markets.