Preventing pregnancy toxemia in sheep comes down to one core principle: making sure ewes get enough energy in late gestation to fuel both themselves and their rapidly growing lambs. The disease develops in the final four to six weeks of pregnancy when energy demands spike and ewes can’t eat enough to keep up. With the right nutritional planning, body condition management, and flock sorting, pregnancy toxemia is largely preventable.
Why Pregnancy Toxemia Happens
Understanding the mechanism helps you see why each prevention step matters. In late pregnancy, lambs do roughly 80% of their growing. That growth demands glucose, and the ewe’s body has to produce it faster than at any other point in the year. At the same time, the expanding uterus compresses the rumen, physically limiting how much a ewe can eat. The result is a gap between energy in and energy out, called negative energy balance.
When a ewe can’t get enough glucose from her feed, her body starts breaking down fat reserves as a backup fuel source. That fat breakdown produces ketone bodies in the liver. In small amounts, ketone bodies are a normal alternative energy source. But when they accumulate faster than the ewe can clear them, they become toxic, causing fatty liver, neurological symptoms, and eventually death. Ewes carrying twins or triplets are at the highest risk because their energy demands are the greatest, and ewes that have lambed multiple times may have more difficulty producing glucose and clearing ketones, making them especially vulnerable.
Target the Right Body Condition Score
Body condition score (BCS) on the standard 1 to 5 scale is your most practical tool for assessing whether ewes are set up to handle late pregnancy. A BCS of 2.0 or less before lambing significantly increases the risk of pregnancy toxemia regardless of how many lambs a ewe is carrying. These thin ewes simply don’t have the reserves or the metabolic momentum to meet late-gestation energy demands.
On the other end, overly fat ewes are also at risk. Excess internal fat accumulates around the rumen, further limiting feed intake at exactly the time a ewe needs to eat more. This creates the same energy shortfall that triggers ketone buildup, just from a different starting point. The target for most ewes at lambing is a BCS of roughly 3.0 to 3.5. Research on triplet-bearing ewes found that a BCS of 3.1 to 3.2 at lambing appeared to be near the optimal range for both ewe health and lamb birthweight, and that lamb survival was near maximum when ewes reached lambing at BCS 3.2 to 3.5.
The practical takeaway: assess body condition at breeding and again at mid-pregnancy scanning. If ewes are below BCS 3.0 at scanning, you need to increase their nutrition well before the final month of gestation, because it’s much harder (and riskier) to put condition on ewes in the last few weeks when rumen capacity is already shrinking.
Scan and Sort by Litter Size
Ultrasound scanning at mid-pregnancy is one of the most cost-effective prevention steps you can take. Scanning tells you which ewes are carrying singles, twins, or triplets, and that information lets you feed each group according to its actual needs. A ewe carrying a single lamb has dramatically lower energy requirements than one carrying triplets. Feeding them all the same ration means you’re either overfeeding singles (wasting money and risking fat ewes) or underfeeding multiples (risking toxemia).
After scanning, mark ewes for litter size and sort them into feeding groups. Ewes in poor body condition should be bumped up a group. For example, a twin-bearing ewe with a low BCS should be grouped with the triplets so she gets the extra concentrate supplementation she needs before lambing. This targeted approach produces lambs at optimal birthweight, reduces mortality, and ensures ewes reach lambing with adequate body condition and colostrum quality.
Increase Grain Feeding in Late Pregnancy
Energy and protein requirements in late pregnancy increase rapidly. For ewes carrying twins, those requirements can roughly double compared to mid-gestation. Pasture or hay alone usually can’t meet this demand, especially as rumen capacity shrinks, so grain or concentrate supplementation becomes essential.
The general guideline is to supplement between one-half and one pound of grain per ewe per day, depending on ewe size, breed, and litter size. In colder climates or in flocks where triplets are common, start supplementation four to six weeks before the expected lambing date. In milder conditions with mostly twin-bearing ewes, starting at four weeks before lambing may be sufficient.
The critical rule is to introduce grain gradually over several days. A sudden jump in concentrate feeding can cause acidosis and actually reduce feed intake, making the energy gap worse. Start with a small amount and increase steadily over a week or more until you reach the target ration. For triplet-bearing ewes, you’ll likely be pushing toward the higher end of the supplementation range (closer to one pound per day or more), while single-bearing ewes in good condition may need little to no grain.
What to Feed
Energy-dense grains like corn, barley, or commercial ewe concentrate mixes are standard choices. The goal is to pack as many calories as possible into a small volume, since the ewe’s stomach space is limited. Some producers also use molasses-based liquid supplements or energy drenches containing propylene glycol or glycerol for individual high-risk ewes that are already showing signs of reduced intake. These provide a rapid, concentrated glucose source, but they work best as a targeted intervention for at-risk animals, not as a substitute for a well-planned feeding program across the flock.
Minimize Stress in Late Gestation
Any event that causes a ewe to stop eating, even briefly, can tip the energy balance in the wrong direction during late pregnancy. Stress triggers include transport, yarding for extended periods, severe weather events, sudden feed changes, and competition at the feed trough from dominant ewes pushing subordinate animals away.
Practical steps to reduce stress in the final six weeks of pregnancy:
- Adequate trough space: Make sure every ewe can access feed at the same time. If subordinate ewes are being pushed out, they’re the ones most likely to develop toxemia.
- Shelter and weather management: Cold, wet, or windy conditions increase energy demands. Providing windbreaks or shelter reduces the caloric cost of staying warm.
- Limit handling: Avoid unnecessary yarding, transport, or shearing in the final month of gestation. If shearing must happen, do it earlier in pregnancy and provide extra feed immediately after.
- Consistent routine: Feed at the same times each day. Irregular feeding schedules can reduce overall intake.
Know Which Ewes Are Highest Risk
Prevention is most effective when you concentrate your attention on the animals most likely to develop problems. The highest-risk ewes share a few common traits:
- Carrying multiples: Twin and especially triplet-bearing ewes have the greatest energy demands and the most rumen compression.
- Too thin or too fat: Ewes with BCS below 2.0 or above 4.0 at the start of late gestation are both vulnerable, though for different reasons.
- Older, multiparous ewes: Ewes that have lambed several times may have reduced capacity to produce glucose and clear ketone bodies.
- Ewes on poor pasture: If forage quality is low due to drought, season, or overgrazing, the baseline diet may not come close to meeting needs.
Identifying these animals early, ideally at scanning, gives you time to adjust their nutrition before the critical last month when things can deteriorate quickly.
Spotting Early Warning Signs
Even with good prevention, individual ewes can still develop problems. The earliest sign is usually a ewe separating from the flock and showing reduced interest in feed. She may appear dull, stand with her head down, or lag behind when the group moves. As the condition progresses, you may notice teeth grinding, muscle tremors, unsteady walking, and a distinctive sweet or acetone-like smell on the breath.
Handheld ketone meters designed for livestock can detect elevated blood ketone levels before obvious clinical signs appear. Routine spot-checking of high-risk ewes in the final weeks of pregnancy can catch subclinical cases early, when intervention is still effective. Once a ewe is down and unresponsive, the prognosis is poor regardless of treatment. Prevention and early detection are far more effective than trying to reverse advanced disease.