Caring for a pregnant mare: stage by stage, the EHV vaccine, and the complications to know

By Sebastien Kister

Last reviewed 8 November 2026

A mare carries her foal for about eleven months, and for most of them she needs little more than she did before: the same forage, her exercise, her vaccines and her feet kept up. What changes is the last third, when the foal does most of its growing, and the foaling itself, where minutes count. This page takes the pregnancy stage by stage, with what the American veterinary sources say at each, the vaccines and paperwork that are particular to the US, then the complications worth knowing by their signs.

The pregnancy at a glance

The dates of each step, from the day she was bred, are on the foaling date calculator, which also gives the due date and the normal window around it. In outline:

Feeding her through the pregnancy

For most of the pregnancy, a mare needs no more than she did before she was bred. The National Research Council's 2007 figures, as the Merck Veterinary Manual gives them, leave her energy needs unchanged until month five, then raise energy, protein and lysine by "approximately 3–4% over maintenance each month". For a 1,100 lb (500 kg) mare not in work, that is:

Protein rises faster at the end: 21%, 25% and 30% above maintenance in months nine, ten and eleven. That is when the foal grows: the Western College of Veterinary Medicine puts 65 to 70% of its growth in months eight to eleven, and Merck's chapter on the mare and foal expects her to gain 150 to 200 lb (68 to 90 kg) over the last three months. The same college adds that before month eight, a mare on good feed needs nothing extra, which the NRC's few percent barely contradict.

How to give it matters as much as how much:

• Gradually. Merck asks for "a gradual, increasing plane of nutrition" in the last three months. The University of Kentucky's advice: raise her feed slowly, over seven to fourteen days, never by dramatic amounts.
• Denser, not just more. In the last two months the foal takes room, and Merck notes that she may eat less roughage. The ration's energy then has to come from a concentrate, Merck suggesting one of 12 to 14% protein, or, if she holds her condition on forage alone, from a ration balancer, as Kentucky advises.
• The same hay. Kentucky would keep her on the hay she knows; if it has to change, start the change at least a week to ten days before she foals.
• No tall fescue at the end. Tall fescue infected with its endophyte, extremely common in the "fescue belt" of the upper Southeast and the Midwest and found well beyond it, causes the foaling problems described below; Penn State advises taking her off high-risk pasture 90 days before she foals.

Her condition

Not too thin, not too fat, and the sources do not quite agree on the number. Merck's nutrition chapter keeps broodmares at a body condition score of 5 to 6 out of 9, 6 being ideal, and Kentucky aims for 5 to 6 in late pregnancy. Merck's chapter on the mare and foal puts the ideal at foaling higher, at 6.5 to 7.5. On why it matters they agree: a mare that is too fat runs more risk of metabolic trouble, laminitis and a difficult foaling; one too thin milks poorly and is harder to get back in foal, and, as Extension Horses notes, condition is very hard to put on once she is feeding a foal. The weight calculator tracks her from a tape measure.

Minerals: more is not safer

• Iodine. Merck reports iodine poisoning in pregnant mares eating as little as 40 mg a day, and goiter in mares and their foals, several cases from kelp supplements.
• Selenium. The margin between too little and too much is narrow, and some forages carry enough to poison. Too little in the mare's diet, and her foal can be born with nutritional myodegeneration, the muscle disease also called white muscle disease. Whether her ration needs selenium depends on where it was grown: ask your vet before adding any.
• Copper. Studies disagree on whether extra copper for the mare protects her foal's joints: one trial found fewer lesions, two later ones found no effect.

Exercise and riding

Merck asks for "adequate daily exercise in a paddock or pasture" right through the pregnancy. Riding is less settled. Two small studies found no harm from moderate work: mares exercised for 45 minutes six days a week from day 16 to day 80 of pregnancy all went on to deliver healthy foals, and in six pregnant Standardbreds put through short graded treadmill tests at about nine months, the foal's heart rate did not change. No veterinary body we found sets a date by which riding must stop, so how long to keep her in work is a question for your vet, and the answer may depend on her and on the work.

Vaccines: the two licensed against EHV abortion

The AAEP names two vaccines licensed for the control of EHV-1 abortion, Pneumabort-K and Prodigy, and its guidelines have a pregnant mare vaccinated "during the fifth, seventh, and ninth months of gestation using an inactivated EHV-1 vaccine licensed for prevention of abortion". Many vets add a dose in the third month, and some one at breeding. Merck Animal Health's label for Prestige Prodigy asks for the same three months, and for maiden and barren mares kept with pregnant mares to be vaccinated on the same schedule; the AAEP has every horse on a breeding farm, or in contact with pregnant mares, revaccinated against EHV every six months.

The vaccine lowers the risk; it does not remove it. In the study behind Prodigy's US license, mares vaccinated at five, seven and nine months were exposed to the virus 20 days after the third dose, and 2 of the 19 still pregnant aborted an EHV-1-positive fetus, against 7 of 22 unvaccinated mares. The one modified-live EHV-1 vaccine is indicated against respiratory disease, and is not among those the AAEP counts as licensed against abortion.

The boosters before foaling. Four to six weeks before she is due, the AAEP's chart for broodmares boosts the core vaccines, Eastern and Western encephalomyelitis, tetanus, West Nile and rabies, along with influenza and an EHV vaccine labeled against respiratory disease, so that her colostrum carries the antibodies to the foal. Rabies can instead be given after foaling, before she is bred again, which takes one shot off the list before the birth. Where the risk calls for them, the same chart adds Potomac horse fever and a killed strangles vaccine at the same time, and two three-dose courses that start in the eighth month: rotavirus, and botulism for a mare never vaccinated against it. The equine viral arteritis vaccine, which the chart keeps for high risk, is the exception: a mare in foal is vaccinated only after foaling, and no less than three weeks before she is bred.

Early in pregnancy, the sources hold off: the University of Minnesota gives no vaccine in the first 60 days, and Merck's chapter on the mare and foal says vaccination is avoided in the first 90. The vaccination guide covers the rest of her program.

Deworming

Deworming is safer than many owners think. Merck says "most anthelmintics are safe for use throughout pregnancy", provided the warnings on the label are followed. The label is where the exceptions are: fenbendazole was tested in mares at every stage of pregnancy with no effect on reproduction, but its five-day larvicidal course, against the migrating larvae of the large strongyle, "has not been evaluated" in pregnant mares. In a study of ivermectin with praziquantel, twenty mares dosed at three times the dose every two weeks until they foaled, and their foals, showed no ill effect.

Around the foaling, the sources disagree outright. Merck advises ivermectin or a benzimidazole one to three days before foaling, against the threadworm Strongyloides westeri, which reaches the foal through the milk. The AAEP's parasite guidelines say there is "no basis" for that practice at present, and the University of Kentucky's parasitologist Martin Nielsen advises treating pregnant mares like any other adult, having found no rise in their egg counts around foaling. Others deworm the mare after the foaling instead, from within 48 hours (another Merck chapter) to about a week (Colorado State). Which your vet follows is their call; a fecal egg count says whether she needs a dewormer at all. The deworming guide explains the counts.

Feet, teeth and the Caslick

We found no guidance that changes a pregnant mare's routine care: Merck's intervals, a trim about every six weeks and teeth checked at least once a year, still apply (the farrier and dental guides have the detail). If work on her needs a sedative, that is your vet's decision: the studies of sedatives in pregnant mares are small.

A mare stitched with a Caslick (a vulvoplasty, which closes the top of the vulva against infection) must be opened before she foals, or the foal will tear her. Merck says about two weeks before, Nebraska Extension at least 30 days. EquiDiary's pregnancy plan offers it as a step of its own.

The paperwork: Coggins, CEM and the foal's registry

Shipping her to the stallion or a foaling farm. Every state requires a negative Coggins test, for equine infectious anemia, before a horse crosses its line, dated within six or twelve months or by calendar year depending on the state, and most want a certificate of veterinary inspection from the last 30 days, which only a licensed vet can issue (USEF). The horse papers guide has the detail.

Contagious equine metritis. A disease spread at breeding, by artificial insemination with infected semen and on hands and instruments. The US is considered free of it, so it is reportable at both federal and state level; mares and stallions imported from countries that have it are quarantined and tested before they enter, and it was last detected here in 2024. A stallion carries it without signs; in a mare it shows as a vaginal discharge, infertility or an abortion (USDA APHIS).

Registering the foal. Each breed registry has its own rules, so read yours before the foal arrives. The Jockey Club starts with a Live Foal Report, due within 30 days of foaling, then sends a kit for the microchip and a DNA sample from the foal's hair (as the Canadian Thoroughbred Horse Society, which registers Canadian-breds with it, sets out); it has required the microchip since the 2017 foal crop. AQHA registers a foal only once both parents have been DNA-typed and the stallion's owner has filed the breeding report, which is due by November 30.

Getting ready to foal

The place. A stall of at least 14 × 14 ft (4.3 × 4.3 m), say Penn State Extension, Nebraska Extension and Merck, which finds a double stall of 12 × 20 ft (3.7 × 6.1 m) better still. A small grass paddock works too; Penn State prefers it to a dry lot, and Merck notes that mares do well foaling outdoors on turf, weather permitting. Wherever it is, it is where she should already be living: the calculator dates the move.

The bedding. Straw, deep and clean. Penn State advises against shavings, whose dust raises the risk of respiratory infection, and Merck because they get into the newborn foal's nostrils and mouth.

The kit. The AAEP's foaling checklist names a clean tail wrap, an umbilical disinfectant, towels, warm water with a mild soap, scissors, gloves and a Brix refractometer, which tells you in seconds whether her colostrum is good enough. Colorado State's longer list adds a thermometer, milk-calcium test strips and foal IgG tests; Penn State's puts the vet's number at the top, with a flashlight, a halter and a lead rope. When labor starts, wrap her tail and wash her vulva and udder (Nebraska, Penn State).

The signs. How the udder fills, waxing, and the milk tests that predict the night are on the foaling calculator.

The foaling, and its time limits

A mare's labor has three stages, and the second is short: a foal held up in it, or with its cord squeezed, runs short of oxygen (the Western College of Veterinary Medicine).

What normal looks like. A white, glistening membrane (the amnion) first, then two front feet, soles down, one a hand's width ahead of the other (Merck puts it at about 15 cm, some 6 inches), then the nose lying on them, "a diving position", as Penn State puts it. Anything else is a call to the vet right away: one foot only, soles pointing up, a nose without feet, a tail, or a red membrane instead of the white one, which is the emergency called a red bag, below.

The placenta. Never pull it, and never cut it away. Tie it up so that she cannot step on it, and keep it for the vet, who checks that it came away whole (the AAEP, Penn State, Colorado State): a piece left inside can make her very ill. Handle it with gloves. A normal one weighs about a tenth of the foal (Merck).

The first hours: the 1-2-3 rule

The AAEP's foaling sheet gives it as: the foal stands within one hour, nurses within two, and within three passes its first manure (the meconium), while the mare passes the placenta. Colorado State's version is the same without the meconium. Merck is a little more patient: in nine foalings out of ten, the foal lies on its chest within an hour, stands within two and nurses within three. A foal behind those times needs the vet.

A foal takes its first antibodies from the colostrum, and can absorb them only in the first 18 to 24 hours (Merck, Cornell). That is why the vet's check of the newborn is usually made at 12 to 24 hours (Colorado State, Penn State, Cornell), with a blood test for IgG, the antibodies the colostrum passed on. Below 400 mg/dL at 24 hours the transfer has failed, and 400 to 800 is partial (Merck); below 800, Merck's chapter on the mare and foal has the vet give plasma. The Brix refractometer in the kit reads the colostrum before the foal does: above 30% is excellent, below 20% not enough (Cornell).

Merck has the navel dipped in 0.5% chlorhexidine or 1% povidone-iodine. Most foals pass the meconium within a few hours, some not for nine to twelve (Penn State); a foal straining without result, or none passed by 24 hours, needs the vet.

After the foaling

A reddish-brown discharge in the first week is normal; a white one may be an infection and needs the vet (Nebraska Extension). Colic after foaling needs more care: mild cramps are common, but in an older mare, colic with pale gums is the sign of the bleeding described below. Her foal heat comes 5 to 11 days after foaling in most mares (Merck). Mares bred after day 10 conceive more often, and Merck advises against breeding on it at all after a difficult foaling or a retained placenta. In a study of over 3,000 cycles on one Kentucky Thoroughbred farm, mares bred before day 22 were less likely to conceive and those bred before day 13 more likely to lose the pregnancy.

Complications, and the signs an owner sees

Most pregnancies run their course with none of what follows. Each is here for the signs an owner can see, because in most of them what decides the outcome is how soon the vet is called.

Twins

A mare's uterus cannot carry two: the placenta that two foals share is too small, and Colorado State puts the chance that a twin pregnancy ends with two live, healthy foals at under 10%. Left alone, twins are usually aborted at seven to nine months (Colorado State; eight to nine, says Merck), sometimes after the udder has filled early. This is what the first ultrasound at days 14 to 16 is for: the vet can see both embryos and pinch one out while they still move around the uterus, before they settle at about day 16. Thoroughbreds, warmbloods and draft breeds have twins most often (Colorado State), and twins were the cause of about 6% of the losses that diagnostic laboratories investigated in Kentucky and in the UK.

Early pregnancy loss

In 2,246 Thoroughbred pregnancies on 29 UK studs, 6.4% were lost between day 15 and day 42, and 1.6% more by day 65; another study put the loss from day 15 to day 65 at 7.9%, the odds rising with each year of the mare's age. There is nothing to see: the mare may simply come back into heat. Only an ultrasound finds it, which is what the later checks in the calendar are for.

Abortion, and what to do if it happens

Later in pregnancy a mare can lose her foal to an infection — of the placenta, below, or EHV, equine viral arteritis or leptospirosis — or to something else: twins, a twisted umbilical cord, fescue, a high fever or a severe illness (the AAEP's guidelines on infectious abortion). Often there is no warning at all. If it happens:

• Keep the fetus and the whole placenta and get them to your vet or the diagnostic laboratory, kept cool in a cooler with ice packs (the AAEP) but never frozen (Merck). Only a laboratory can say why, and the answer decides what the other mares need, though even two large Kentucky series of aborted fetuses, stillborn and newborn foals found no cause in about one case in six.
• Handle them away from other pregnant mares, somewhere easy to disinfect such as a wash rack, and do not spray or hose them, which can put the virus in the air (the AAEP's abortion guidelines); its EHV guidelines have them put in doubled plastic bags at once.
• Isolate the mare, move no in-contact mare out and no new one in until there is a diagnosis, and bag her bedding rather than spread it on a pasture (the University of Kentucky).

EHV-1 abortion

The equine herpesvirus aborts mares from about the seventh month, most often in the last third of the pregnancy, from two weeks to several months after the infection, and the mare shows nothing beforehand (Merck, the AAEP). The fetus is often born still inside its membranes. A mare infected late may instead have a foal that is ill from birth and usually dies within days. It spreads among pregnant mares, and although single cases are now the rule, outbreaks of several abortions still happen (Kentucky). The AAEP's guidelines keep exposed horses isolated until 14 to 28 days after the last signs in any of them. The vaccine at five, seven and nine months, above, and keeping pregnant mares away from horses that travel to shows (Merck) are the prevention, though a vaccinated mare can still abort.

Placentitis

An infection of the placenta, usually climbing in through the cervix, and one of the main causes of late abortion, of foals born early and of foals that die in their first day (Merck): the University of Kentucky puts it behind nearly a third of late abortions and of deaths in a foal's first day. The signs: an udder that fills, or milk that runs, weeks or months before she is due — an udder should develop in the last couple of weeks, Colorado State says, not months — and a discharge from the vulva. Call the vet promptly: treatment works best when it starts early, and does not always work (Kentucky). A Caslick for a mare whose vulva does not close well, and clean breeding, are the prevention (Merck). One form, nocardioform placentitis, first described in the US in the mid-1980s (Merck), was an important cause of chronic placentitis in the Kentucky series.

Milk before foaling

Milk that runs before the foal is born, whatever the cause (placentitis, twins, an abortion on its way), is colostrum the foal will not get, and Merck lists it among the reasons a foal fails to receive its antibodies. Call the vet, who may have it milked and frozen for the foal (Extension Horses), and make sure the foal's IgG is tested after the birth. The Brix refractometer grades the colostrum she has left: under 15% poor, 15 to 20% borderline, 20 to 30% adequate, over 30% good (the AAEP).

Hydrops

Too much fluid around the foal, usually the allantoic fluid (hydrallantois), building up over days to weeks in the last third of the pregnancy. The belly grows suddenly — in one reported case of hydramnios, from 230 to 320 cm around (about 91 to 126 inches) in six days — with a painful swelling underneath, reluctance to walk, labored breathing, colic or a mare off her feed. It is rare and an emergency, because the weight can tear the body wall. In a Kentucky hospital series of 30 mares over ten years, 27 of 30 mares survived, and 95% of those bred again had a foal.

Body wall tear and prepubic tendon rupture

Late in pregnancy, mostly in older mares and after hydrops, the wall of the belly, or the tendon that anchors it to the pelvis, can give way under the weight. The signs: a sudden swelling along the underside, often with a lot of edema, a mare unwilling to walk, and the udder pushed forward. Call the vet now. A mare with a torn wall cannot push the foal out herself, so the foaling is assisted or a cesarean (the Western College of Veterinary Medicine). In a series of 13 mares, foals did better when the birth was not induced.

Uterine torsion, and colic in a pregnant mare

The uterus can twist on itself in the second half of the pregnancy or at foaling, cutting the foal's blood supply. What you see is colic, severe or subtle, easily taken for gut pain or for the start of labor. It usually needs surgery; in one series, 97% of mares and 72% of foals survived when it happened before day 320, against 65% and 32% after. Any colic in a pregnant mare needs the vet: of the pregnant mares one referral hospital treated for colic, 70% went home, and a fifth of the pregnancies then ended badly.

A difficult birth (dystocia)

Most difficult births are a foal in the wrong position, rarely one too big to pass (Merck), and for the foal, minutes count. In a study of over a thousand births, a second stage longer than 40 minutes significantly raised the foal's risk of dying, and only 37% of foals survived once a dystocia had to be resolved at a hospital. Call the vet if there is no progress 15 to 20 minutes after the water breaks, or for one foot only, more than two, feet upside down, a nose without feet, feet without a nose, or a foal coming backwards (Extension Horses, the American College of Veterinary Surgeons). While you wait, walk her, so that she does not lie down and strain, and do not pull on the foal unless the vet tells you to (Penn State).

Red bag

The membrane that appears first should be white. If a red, velvety one appears instead, the placenta has come away from the uterus before the foal is out and the foal is losing its oxygen: Merck calls it the most acute cause of a foal's asphyxia. Call the vet, and do not wait for them: Merck, Colorado State and Penn State all say to cut or tear the red membrane open and deliver the foal, carefully, so as not to cut it, which is why scissors are in the kit. Colorado State links it to placental infection, fescue and stress.

Retained placenta

A placenta not passed within three hours is retained (Merck, the AAEP, Penn State and most others), which happens in 2 to 10.6% of mares, Friesians more than most (Merck). In a mare it is serious: it can bring an infection of the uterus, endotoxemia and laminitis (Merck). Do not pull it; tie it up and call the vet.

Bleeding after the foaling

An artery to the uterus can tear, most often in older mares: in Kentucky's post-mortem records, 78% of the 513 mares that died of it were 15 or older. Younger mares are not spared: in 73 cases referred to a hospital, the median mare was 14 and had had eight foals, the youngest was 5, and the authors found it can happen at any age and after any number of foals; 86% of those mares bled after the foaling rather than before. The signs are those of colic — pawing, sweating, rolling — then of shock, with pale gums and a racing heart; or sudden death. A mild case can pass for the cramps that often follow a foaling, which is why a mare that seems uncomfortable afterwards should be seen. Call the vet now.

Hyperlipemia in ponies, miniatures and donkeys

A pony, a miniature horse or a donkey that stops eating can flood her blood with fat until her liver and kidneys fail, and late pregnancy is the classic time (Merck): in a UK series, 9 of the 14 mares affected were in foal, and 12 of the 18 animals were fat. The signs are dullness, not eating, weakness, and later a swelling under the belly, colic and trembling. Call the vet the same day: two in three animals in that series died.

Fescue and mare reproductive loss syndrome

Two American problems. Tall fescue infected with its endophyte lengthens the pregnancy and brings a thickened or retained placenta, red bags, little or no milk and weak foals (Penn State, Merck): Penn State advises taking mares off it up to 90 days before foaling, which is the step the app offers unticked, for the mares that graze it. Mare reproductive loss syndrome struck Kentucky in 2001, when mares swallowing eastern tent caterpillars aborted early and late, and about 30% of that year's Thoroughbred foal crop was lost (Kentucky); controlling the caterpillars on the pasture prevents it.

Tears in the birth canal

Most happen at a first foaling, with a large or badly placed foal or a forceful assisted delivery. They are graded from first degree to third, which runs through the anal sphincter; a foot pushed up through the roof of the vagina leaves a hole into the rectum, a rectovaginal fistula. Check her for tears after the foaling (Penn State); the repair usually waits four to six weeks.

Related guides

• Foaling date calculator — the due date, the normal window and every step dated from one day
• Horse vaccination schedule — the core vaccines and how often boosters are really due
• Horse deworming schedule — fecal egg counts, and why a dewormer every two months is out
• Horse papers in the US — the Coggins, health certificates and state rules
• Horse feeding plan — forage, concentrates and the fescue problem

Sources

• Merck Veterinary Manual — Nutritional requirements of horses (2026: the NRC's needs by month, condition, minerals) and its table of energy needs in pregnancy; Perinatal mare and foal care (feeding, condition at foaling, exercise, vaccines, the foal's first hours); Parasite control during pregnancy; Parturition (stages, the Caslick, red bag); Dystocia; The early postpartum period (foal heat); Failure of transfer of passive immunity; Abortion in horses and its reproductive-system chapter (twins, EHV, placentitis, MRLS); Retained fetal membranes; Neonatal encephalopathy (red bag); Hyperlipemia; Nutritional myopathies (selenium); Fescue poisoning; Dental, coat and hoof care
• AAEP — Equine alphaherpesvirus vaccination guidelines (2025: the vaccines licensed against abortion, the months, the six-month interval on breeding farms); Adult horse vaccination chart (the broodmare column: boosters 4–6 weeks before foaling, rotavirus, botulism, EVA); Foaling monitor sheet (2025: the kit, the time limits, the 1-2-3 rule, colostrum grades); Equine infectious abortion field diagnostic guidelines (2026); EHV-1 and EHV-4 guidelines; Internal parasite control guidelines (deworming at foaling)
• Merck Animal Health — Prestige Prodigy (manufacturer: the label's schedule, maiden and barren mares); USDA APHIS — Summary of studies supporting product licensure, Prodigy (compiled 2018: the challenge study in pregnant mares) and Contagious equine metritis
• USEF — Interstate travel for horses (the Coggins and the certificate of veterinary inspection)
• Registries: Canadian Thoroughbred Horse Society — Foal registration (The Jockey Club's Live Foal Report, the kit); The Jockey Club — microchips required from the 2017 foal crop (2016); AQHA, What is needed to register my foal and Filing the stallion breeding report
• University of Kentucky — Broodmares' nutritional needs during late gestation (2012); Sustainable equine parasite control (2012); Placentitis research (2009); Manifestations of equine herpesvirus-1; MRLS foal losses (2009)
• Colorado State University Equine Reproduction Laboratory — Twin management (2022); Red bag in horses (2025); Placentitis in mares (2025); Foaling out: easy as 1-2-3 and Foaling kit checklist (2024); CSU Veterinary Health, Foaling guide (2022)
• Penn State Extension — Foaling season: tips for delivery (2025); When to call the equine vet (2025); Tall fescue toxicosis and broodmares (2024)
• Nebraska Extension G1874 — The foaling mare (2008); Extension Horses — Nutritional considerations for broodmares and Horse foaling management guidelines (2020); University of Minnesota Extension — Caring for your mare (no vaccines in the first 60 days); Western College of Veterinary Medicine — The foaling mare; Cornell — Foal speed ahead (2023); American College of Veterinary Surgeons — Dystocia in horses
• Label: fenbendazole for horses (DailyMed, US National Library of Medicine)
• Studies — exercise: days 16 to 80, 2014, treadmill at nine months, 2009; deworming: ivermectin and praziquantel, 2003; copper: 1998, 2005, 2007; early loss: UK studs, 2018, 2019; causes of abortion: Kentucky, 1993, a second Kentucky series, 1993, UK, 2003; hydrops: Kentucky, 2022, 2021; body wall: 2008; uterine torsion: 2007; colic: 2021; dystocia: 2012, 2024; bleeding: 2008, Kentucky post-mortems, 2012; hyperlipemia: 1992; rebreeding: 2012; tears: 2025

Guidance on pregnant mares is revised as studies come in, and the sources above disagree in places, which this page says where they do. Vaccine labels and registry rules change too; check the current ones. Your vet sets your mare's program.

Next: the foaling date calculator — the due date, the window, and the calendar of the pregnancy.

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