Sheep Gestation: How Long Ewes Are Pregnant

Author: Elliott Garber, DVM

A ewe is pregnant for about 147 days, roughly five months. Most healthy ewes lamb somewhere in a range of about 142 to 152 days from breeding, with some variation by breed, litter size, and individual. To find your due date, count 147 days forward from the day the ewe was bred, then plan your late-gestation feeding, vaccinations, and lambing setup around it.

How long is a ewe pregnant?

The normal gestation period for a ewe is approximately 147 days, according to New Mexico State University, which puts the usual range at 144 to 152 days. Montana State University Extension cites an average of about 147 days with individual pregnancies varying from roughly 138 to 159 days. So while five months is the number worth memorizing, do not be surprised if a given ewe lambs a few days on either side of it.

Several things nudge the actual length:

• Breed. Some breeds run consistently a couple of days shorter or longer than the 147-day average. If you keep good records across seasons, you will learn your own flock’s tendencies.
• Litter size. Ewes carrying twins or triplets often lamb slightly earlier than ewes carrying a single lamb.
• The individual ewe. It is not unusual for individual ewes to vary in gestation length by three to five days from one pregnancy to the next.

Because the window is fairly tight, an accurate breeding date is the single most useful thing you can have on hand. If you run a ram with the flock, a marking harness (a crayon that leaves color on the ewe’s rump when she is bred) tells you who was covered and roughly when, which is how you turn a vague “sometime in October” into a real due date.

Counting forward to your lambing date

The math is simple: take the day the ewe was bred and add 147 days. That lands you in the middle of the normal range, which is exactly where you want your preparation to peak. Then work backward from that date to schedule the two things that are genuinely time-sensitive: the pre-lambing CD&T booster (about two to four weeks out) and having your lambing area ready (a week or two out, so an early ewe never catches you flat-footed).

Keeping the breeding date, the calculated due date, and each ewe’s history in one place is where a records system earns its keep. In Creatures you can add each ewe as an animal, log her breeding date, and set a reminder for upcoming care so the CD&T booster and lambing-prep dates surface on their own instead of living in your head. If you want a quick starting point for the estimate, the parent sheep species hub links out to the rest of the flock-management guides in this series.

The three trimesters, and where the work is

Ewe pregnancy is usually split into early, mid, and late gestation, but the effort is very lopsided toward the end.

Early and mid gestation (roughly the first 15 weeks). The embryo implants and the placenta develops, but the fetus itself stays small. A ewe on decent pasture or good hay at maintenance usually needs little more than that, plus clean water and free-choice minerals. Do not over-condition her here. A fat ewe going into late gestation is at higher risk of trouble, not lower.

Late gestation (the last 6 weeks). This is the part that matters most. Around 70% of fetal growth happens in the last four to six weeks of pregnancy, according to Oregon State University Extension. The lambs are packing on weight fast, and at the same time they are taking up so much room that the ewe physically cannot eat as much bulky forage as she could earlier. That combination, high demand plus shrinking rumen space, is the whole reason late-gestation nutrition is where problems appear.

Feeding the ewe in late gestation

Getting the last six weeks right prevents most pregnancy problems and sets up healthy lambs and a good milk supply. Getting it wrong, in either direction, is how ewes end up in metabolic trouble.

The core idea: energy and protein need to climb in late pregnancy, but the increase has to be gradual. A ewe carrying twins needs substantially more energy than one carrying a single, and one carrying triplets more still. In practice that usually means adding some grain or a higher-energy ration on top of good forage during the last four to six weeks, introduced slowly over one to two weeks so the rumen adjusts and you avoid a grain-overload situation. Your local extension office or veterinarian can help you build a ration to your ewes’ body condition and expected litter size, since the right amount depends heavily on both.

A few principles hold regardless of the exact numbers:

• Feed to body condition, not to a fixed scoop. Thin ewes need more; over-conditioned ewes are a problem you should have headed off earlier. Run your hands over the loin and check condition through the fall so you are not trying to fix it in the last three weeks.
• Make every change slowly. The rumen is a fermentation vat with a resident microbe population, and abrupt feed changes are a direct trigger for metabolic disease (more on that below).
• Keep clean water and free-choice minerals available. For deeper coverage of what those minerals should include, see the sheep minerals guide, and for building the base ration, the sheep feeding guide.

Pregnancy toxemia (ketosis)

Pregnancy toxemia, also called ketosis or twin-lamb disease, is the metabolic disease every shepherd needs to understand before lambing. It happens in late gestation when the ewe cannot take in enough energy to meet the demand of her growing lambs, so her body starts breaking down its own fat for fuel, which floods her system with ketones. The Merck Veterinary Manual describes the primary cause as inadequate energy intake in late pregnancy, made worse by the reduced rumen capacity that comes with a belly full of lambs. Untreated, it can be fatal, and death rates in untreated cases are high.

The ewes most at risk are those carrying twins or triplets, ewes that are either too thin or too fat, and any ewe whose feed is suddenly cut back or interrupted (bad weather, a move, running out of grain) in the last few weeks. Early signs to watch for include a ewe going off feed, standing apart from the flock, dullness or weakness, a wobbly or uncoordinated gait, and sometimes apparent blindness or teeth grinding.

Pregnancy toxemia is an emergency. If you see these signs in a late-pregnant ewe, call your veterinarian right away rather than waiting to see if she improves. Prevention is far more reliable than treatment: keep late-gestation energy adequate, keep ewes in moderate (not fat, not thin) condition, and never let feed intake stall out in the final weeks. Cornell Small Farms has a useful primer on telling it apart from milk fever, which can look similar.

Milk fever (hypocalcemia)

Milk fever, or hypocalcemia, is the other late-gestation metabolic disease, and it is easy to confuse with pregnancy toxemia. It is a sudden drop in blood calcium, and in ewes it typically shows up in the last six weeks of pregnancy rather than after lambing (which is the opposite of the pattern in dairy cows). According to the Ohio State University Small Ruminant Team, onset is often abrupt and frequently follows within about 24 hours of a stressor: an abrupt change of feed, a sudden change in weather, or a short period of fasting caused by handling, shearing, or transport.

Early signs can include a stiff gait, unsteadiness, drooling, and a ewe that becomes weak and goes down. Like pregnancy toxemia, this is a call-the-vet situation, not a wait-and-see one, and the two conditions can occur together. The practical prevention overlaps neatly with everything above: avoid sudden feed changes, minimize stressful handling in the last weeks, and keep the late-gestation ration and minerals steady. If you must handle or move heavily pregnant ewes, do it gently and keep the disruption short.

Vaccinating and prepping the ewe before lambing

Two jobs in the final month protect the lambs before they are even on the ground.

The pre-lambing CD&T booster. CD&T protects against clostridial diseases (types C and D of overeating disease, plus tetanus). A newborn lamb is not born immune to these. It gets its protection secondhand, through antibodies in the ewe’s colostrum, the thick first milk. To load that colostrum with antibodies, you boost the ewe before she lambs. Michigan State University Extension and the widely cited Maryland small-ruminant program both recommend vaccinating the ewe about two to four weeks before lambing so those antibodies are at their peak in her colostrum. A ewe that has never been vaccinated needs two doses in late pregnancy (commonly around six and three weeks out) to be properly protected the first time. Follow the label and your veterinarian’s guidance on product and timing. For the full schedule, including the lambs’ own series, see the sheep CD&T vaccine guide.

Crutching. In the last couple of weeks, crutch the ewe: shear the wool away from around the udder and the rear end. This keeps the birth area cleaner, makes it far easier for a newborn lamb to find the teat instead of latching onto a wool tag, and lets you actually see the udder and vulva as lambing approaches. It is a small job that pays off in the first hour of a lamb’s life. If you are shearing the whole flock ahead of lambing anyway, the sheep shearing guide covers the full-body version.

Log the CD&T booster and the crutching date on each ewe’s health and medical record so next year’s schedule is already half-written and you can see at a glance which ewes are covered.

Preparing for lambing

As the due date closes in, set up lambing jugs: small individual pens, usually around five feet by five feet, where a ewe and her new lambs bond undisturbed for the first day or two. Have them clean, dry, well bedded, and ready a week or two before your earliest ewe is due, because the one time you skip this is the year a ewe lambs early. Stock a lambing kit nearby (clean towels, iodine or chlorhexidine for navels, colostrum on hand as backup, a lamb sling or scale, and your vet’s number) so you are not scrambling at 2 a.m.

Watch for the signs a ewe is close: udder filling and tightening, the vulva softening and swelling, the ewe separating from the flock, pawing at the bedding, and restlessness. The full play-by-play of a normal delivery, when to step in, and when to call for help lives in the lambing guide. If a lamb ends up needing supplemental feeding, the bottle-feeding lambs guide walks through it.

Once lambs arrive, add each one as an animal and record its birth date, dam, and sire while the details are fresh. If you keep pedigrees or plan to sell breeding stock, that record is what makes a lamb’s history real to a future buyer later on. You can see how the different profile tabs hold breeding, health, and lineage information as your flock grows.

Frequently asked questions

How do I calculate a ewe’s due date?

Add 147 days to the breeding date. That puts you in the middle of the normal 142-to-152-day window. Then schedule the pre-lambing CD&T booster about two to four weeks before that date and have your lambing area ready a week or two ahead.

Can I tell how many lambs a ewe is carrying?

Not reliably by eye. A veterinarian can ultrasound ewes in mid-gestation to count fetuses, which is genuinely useful, because it lets you feed the twin- and triplet-bearing ewes more heavily and separate them from the singles. Knowing litter size is one of the best tools you have for preventing pregnancy toxemia.

Why does late gestation matter so much more than early?

Because about 70% of the lamb’s growth happens in the last four to six weeks, while the ewe’s rumen is being crowded by that same growth. Energy demand is peaking exactly when her physical capacity to eat is shrinking, which is the setup for both pregnancy toxemia and milk fever if nutrition is not managed carefully.

Should I change my ewe’s feed right before lambing?

Increase energy in late gestation, yes, but do it gradually over one to two weeks, not overnight. Sudden feed changes are a direct trigger for both metabolic diseases. Any big shift in the last few days should be discussed with your veterinarian.

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