Pregnancy toxaemia strikes ewes carrying twins or triplets, 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 occur in 10% or more of twin and triplet bearing ewes.
Energy requirements of a ewe in the end stages of pregnancy are double that of a non-pregnant ewe, while twin and triplet bearing ewes need 2.5 to 3 times that energy. 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. 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 and triplet bearing, older ewes and early-lambing ewes preferential or supplementary feed, especially in the final six weeks prior to lambing.
Avoiding all management procedures that involve tipping sheep up (e.g. crutching, involve 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.
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 mobilised from the bone tissue, to provide for the growing lamb in the uterus and mammary development. 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
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.
Lying down on their sternum.
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 ewes are grazing on plantain in late pregnancy they should be lambed on the plantain to avoid calcium levels dropping suddenly.
Also take care not to hold ewes (especially in the last 60 days of pregnancy) off feed for longer than is absolutely necessary.
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 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 back.
If ewes are found dead in the paddock there may be signs of froth around the mouth.
Ask your 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.
Provide Causmag in a lick with salt and lime (crushed limestone).
Dust paddocks with magnesium oxide before grazing if you expect major problems.
Wear a mask when applying the powder.
Check the soil tests to see if potassium levels are excessively high as this can be a predisposing factor.