Caring for a pregnant mare (Canada): stage by stage, the national Code's rules, and the complications to know

By Sebastien Kister

Last reviewed 8 November 2026

A mare carries her foal for about eleven months, 341 days on average, give or take 15, in the figure of Canada's national Code of Practice, and for most of them she needs little more than she did before. What changes is the last third, when the foal does most of its growing, and the foaling itself, where minutes count. Two things are Canadian. The Code sets Requirements for the pregnancy and the foaling, from turnout to a mare watched twice a day near her date, and in Quebec, Prince Edward Island and Newfoundland and Labrador they are law for every horse owner. And when the last months fall in a Canadian winter, the cold adds to what she needs. This page takes the pregnancy stage by stage, 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:

What the national Code requires

The Code of Practice for the Care and Handling of Equines was published in 2013 by the National Farm Animal Care Council (NFACC). It separates Requirements, the minimum "to be implemented by all persons responsible for farm animal care" and enforceable where a federal or provincial regulation says so, from Recommended Practices. Its Requirements for a pregnant mare and her foal are few, and each has a reason:

• Before breeding: do not breed unless you know the basics of care the Code sets out for the mare and the foal, and can provide them.
• The pregnancy: a mare that needs medical care during gestation must receive it, and she "must have some form of exercise or turnout", unless she is on stall rest for medical reasons or severe weather makes it temporarily impossible. Her diet must keep her healthy and let her provide adequate nutrition to the foal.
• The foaling: "a plan must be in place for the foaling process, including a plan for getting prompt expert advice or help if needed", and mares close to foaling "must be observed at least twice a day".
• The foal: it must be watched to make sure it can rise and suck unassisted, given appropriate care without delay if anything is wrong, and it must receive colostrum or alternative care.

Who it binds depends on the province. In Quebec, every owner or keeper of a horse must comply with its Requirements since 10 February 2024, except those on records, the parasite program and a written biosecurity plan, and the Quebec regulation adds one of its own: enough bedding wherever a horse is confined to absorb its urine and encourage it to lie down. In Prince Edward Island, horses, donkeys and mules count as commercial animals, and every owner of a commercial animal must comply with the codes listed in the regulations, the equine Code among them. In Newfoundland and Labrador, the 2013 edition's Requirements bind every owner of horses, ponies, donkeys and mules and the operator of any place they are kept, transport provisions and most appendices excepted. Elsewhere the Code is a reference that each province treats differently; the Canadian feeding guide goes province by province. The Code is being revised: public comments closed on 12 March 2026, and NFACC projects completion in April 2027.

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 500 kg mare not in work, that is:

That is when the foal grows: the Western College of Veterinary Medicine in Saskatoon 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 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.

The Code's recommendations for the last three months are practical:

• A little concentrate. 0.5 to 0.75% of her body weight: the foal compresses her digestive tract and she can hold less hay, poor hay may not meet her needs, and it prepares her for the larger rations of lactation.
• Enough protein: 11% of the diet in late gestation, 13.5% in the first three months of lactation.
• Slowly, and in more than one meal. Any increase in concentrate over 7 to 10 days, split into at least two meals, and no more than 0.5 to 0.6 kg of concentrate per 100 kg of body weight at any one feeding. The University of Kentucky's advice is similar: over seven to fourteen days, never by dramatic amounts.
• 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.

In the cold. Ontario's agriculture ministry puts the lower critical temperature of an adult horse in Canada at −15 °C, below which its maintenance energy rises 2.5% for every degree, and it notes that "in late pregnancy (9th month and beyond), energy requirements of mares increase and, consequently, cold tolerance decreases", although a winter-adapted, well-fed pregnant mare is at no higher risk than a gelding. Good hay is the easiest way to add the energy; the feeding guide has the winter figures.

Her condition

Not too thin, and the sources do not quite agree on how fat. The Code recommends keeping broodmares at a body condition score of 5 to 7 out of 9 through breeding, gestation and lactation, and at least 5 before she is bred: mares too thin at the start of the season or at foaling conceive less often and lose too much weight once they are feeding a foal. It also finds that a score of 7 at foaling is not associated with foaling problems, and warns that late in gestation the flank and the tail head are less reliable places to score her. Merck's nutrition chapter keeps broodmares at 5 to 6, and its chapter on the mare and foal puts the ideal at foaling at 6.5 to 7.5. At 3 or lower, or at 8 or higher, the Code requires corrective action. 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 goitre 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

On exercise the Code makes a Requirement: a pregnant mare must have some form of exercise or turnout, short of a medical reason or weather that makes it temporarily impossible. 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, and the Code recommends asking a vet or an experienced breeder what work suits her in late gestation.

Vaccines, and who sells them

The Code recommends "regionally appropriate" vaccines for broodmares, a vaccination program built with a vet, and a record of every dose, and for guidelines it points to the American Association of Equine Practitioners. The AAEP's are explicit: a pregnant mare is 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. It names two vaccines licensed for the control of EHV-1 abortion in the US, Pneumabort-K and Prodigy, and both are on the list of veterinary biologics licensed in Canada by CFIA, as Pneumabort K + 1B (Zoetis) and Prestige Prodigy (Intervet). Like all 38 horse vaccines on that list, they are of US origin. The list gives no label claims, so which product, and its schedule, is your vet's call. The AAEP also has every horse on a breeding farm, or in contact with pregnant mares, revaccinated against EHV every six months.

The boosters before foaling. The Code's reason for them is the colostrum: vaccinations "should be boosted three to four weeks before the projected foaling date to optimize the antibody concentrations in colostrum". The AAEP's chart for broodmares says four to six weeks, for the core vaccines, Eastern and Western encephalomyelitis, tetanus, West Nile and rabies, along with influenza and an EHV vaccine labelled against respiratory disease; rabies can instead be given after foaling, before she is bred again. Two vaccines in the AAEP's broodmare column are not on CFIA's list at all: rotavirus and equine viral arteritis. 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 Canadian vaccination guide covers the rest of her program.

Who sells them. In Quebec, every animal vaccine is a prescription drug, and so are the common horse dewormers, and the law forbids giving your own horse one obtained without a prescription. In Ontario, licensed livestock medicine outlets, often farm supply, feed and tack stores, sell over-the-counter livestock medicines that need no prescription. Rabies vaccine may be sold only to a veterinarian, anywhere in Canada, save under the Minister's written permission for an emergency clinic or a remote area.

Deworming

The Code recommends making sure the pregnant mare is "appropriately vaccinated and dewormed", and 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 Canadian deworming guide explains the counts.

Feet, teeth and the Caslick

We found no guidance that changes a pregnant mare's routine hoof care: Merck's interval, a trim about every six weeks, still applies. For teeth, the Code recommends a dental examination at least once a year, and names broodmares among the horses that should be checked for problems in particular. 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.

Getting ready to foal

The plan. The Code's Requirement comes first: a plan for the foaling, including how you will get prompt expert advice or help. It also recommends asking a vet for a health plan for the pregnancy, with pre-foaling instructions and the number for emergency care, and arranging for a vet or experienced breeder to be available at the first sign of difficulty.

The place. The Code allows a stall, a paddock or a pasture: large enough for her to move and to lie flat on her side, then to make room for the foal. A box stall for a mare and a foal up to two months old should be at least 30% larger than the average stall, with solid walls, and fencing should not let her or the foal get a leg caught when she lies down. Penn State Extension, Nebraska Extension and Merck give at least 4.3 × 4.3 m (14 × 14 ft). The Code recommends a dry, sheltered area, moving her there several days before the expected date so that she knows it, and a familiar companion nearby if she foals apart from the herd.

The cold. Newborn foals have "very poor cold tolerance" (Ontario's agriculture ministry). The Code says a foal born in bad weather, or weak, premature or sick, should be dried off promptly and given extra shelter, bedding or a foal blanket, which it finds the most practical option. Heat lamps and space heaters can start fires or overheat a foal that cannot move away, and any foal that needs one should be checked often.

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 labour starts, wrap her tail and wash her vulva and udder (Nebraska, Penn State).

The signs. The Code lists the udder developing, the teats distending, the tail head softening, wax on the ends of the teats and the vulva lengthening, and warns that some mares foal without any of them; its Requirement is that she be observed at least twice a day. The milk tests that predict the night are on the foaling calculator.

The foaling, and its time limits

A mare's labour 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). The Code puts it plainly: "a normal foaling takes less than 20 minutes from the time the water breaks", and "if after ten minutes of active labour the foal is not visible, provide appropriate intervention without delay". When you call, be ready to say how many minutes it has been since the water broke.

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), 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 Code, 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 Code recommends a vet's examination of the mare after the foaling, above all if it did not go normally.

The first hours: the 1-2-3 rule

The foal stands within one hour, nurses within two, and within three passes its first manure (the meconium), while the mare passes the placenta: that is the AAEP's foaling sheet, and the Code lists a foal that misses any of the three among the signs of trouble, with lethargy, straining, milk in the nostrils or on the face, grinding its gums and colic. 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; the Code requires care without delay.

A foal takes its first antibodies from the colostrum, which a mare produces only once in each pregnancy, in her last two to three weeks. The Code notes that the foal absorbs them best right after birth and less well from six to eight hours; Merck and Cornell put the limit at 18 to 24 hours. That is why the vet's check of the newborn, which the Code recommends with a test for colostrum intake, and strongly if the foal has not sucked well in its first six hours, 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). The Code recommends planning colostrum with your vet before the birth, and keeping a frozen store of good colostrum or access to one, thawed in warm water, never in a microwave.

The Code recommends treating the navel in its first 24 hours with a product such as 0.5% chlorhexidine, dipping it for 30 seconds each time, and warns that caustic products such as 7% iodine do harm; Merck gives 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.

The paperwork: reportable diseases and the foal's registry

Reportable diseases. Contagious equine metritis, a disease spread at breeding, and equine infectious anemia are federally reportable: an owner, a vet or a laboratory must report a suspected case to CFIA. In Ontario, laboratories report a positive EHV-1 result to the province at once, with CEM and EIA. In Quebec, CEM and EIA are among the diseases whose every sign an owner or keeper must report, and a vet must declare them without delay, as the French version sets out.

The Coggins. CFIA does not require an EIA test to move a horse within Canada, but shows, races, events and sales ask for one, a horse leaving the country needs one, and a horse that tests positive is ordered destroyed, with compensation of up to $2,000. The Canadian papers guide has the border rules, for a mare going to a stallion in the US.

Registering the foal. Each breed has its own rules, so read yours before the foal arrives. The Canadian Livestock Records Corporation keeps the registries of some two dozen horse breed associations, among them the Canadian Horse, the Canadian Sport Horse, the Belgian, the Percheron and the Clydesdale. The Canadian Horse Breeders Association asks for foals to be registered at birth, with fees that depend on the foal's age, then a kit with a microchip for the vet to implant and a DNA parentage test from a hair sample. A Canadian-bred Thoroughbred is registered with The Jockey Club and the Canadian Thoroughbred Horse Society: a Live Foal Report within 30 days of foaling, then a kit for the microchip and a DNA hair sample, and registration within a year of birth to avoid the society's late fee.

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 scan 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 season. Only a scan 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, 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 field (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 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).

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; the Code says that colostrum can be milked and frozen for the foal, and the foal's IgG should be 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 in six days — with a painful swelling underneath, reluctance to walk, laboured 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 caesarean (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 labour. 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 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 (the Code, 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. A donkey's pregnancy runs longer than a mare's, about 365 days, give or take 20, in the Code's figure.

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 (Canada) — the core four, rabies, EEE, and Equestrian Canada's six-month rule
• Horse deworming schedule (Canada) — egg counts, resistance on Canadian farms, and Quebec's prescription rule
• Horse papers in Canada — the Coggins at the border, brand inspection out west, and the EID
• Horse feeding plan (Canada) — the national Code province by province, and feeding below −15 °C

Sources

• National Farm Animal Care Council — Code of Practice for the Care and Handling of Equines (2013), sections 2.2.1, 3.4.5, 4.1.2, 4.3, 4.5 and 7, and the revision under way
• Where the Code is law: Quebec, MAPAQ — guide to the regulation on the welfare of companion animals and equids, article 52, and summary of the regulation (in force since 10 February 2024) (in French); Prince Edward Island, Animal Welfare Act and Animal Welfare Regulations, section 26 and Schedule B; Newfoundland and Labrador, Animal Protection Standards Regulations, section 4
• Ontario Ministry of Agriculture, Food and Agribusiness — Management and feeding of horses in cold weather (2026)
• Vaccines: AAEP, Equine alphaherpesvirus vaccination guidelines (2025) and Adult horse vaccination chart (the broodmare column); CFIA — Licensed veterinary biologics (the list as downloaded on 8 November 2026)
• Who sells them: Gazette officielle du Québec, 7 February 2001 — Regulation respecting the terms and conditions for the sale of medications (Schedule IV) and the text in force (in French); Quebec's Animal Health Protection Act, sections 55.1 and 55.4 (in French); Ontario — Livestock medicine sales in Ontario; Health of Animals Regulations, section 134.2 (rabies vaccine)
• Reportable diseases: CFIA — Federally reportable diseases and EIA control program; USDA APHIS — Contagious equine metritis (how it spreads); Ontario — Notifiable hazards under the Animal Health Act, 2009; MAPAQ's notices to animal owners and keepers and to veterinarians on reportable diseases (February 2026, in French)
• Registries: Canadian Livestock Records Corporation — Associations; Canadian Horse Breeders Association — FAQ; Canadian Thoroughbred Horse Society — Foal registration
• 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; Parasite control during pregnancy; Parturition; Dystocia; The early postpartum period; Failure of transfer of passive immunity; Abortion in horses and its reproductive-system chapter; Retained fetal membranes; Neonatal encephalopathy (red bag); Hyperlipemia; Nutritional myopathies (selenium); Dental, coat and hoof care
• AAEP — Foaling monitor sheet (2025); Equine infectious abortion field diagnostic guidelines (2026); EHV-1 and EHV-4 guidelines; Internal parasite control guidelines
• Western College of Veterinary Medicine — The foaling mare; University of Kentucky — Broodmares' nutritional needs during late gestation (2012), Sustainable equine parasite control (2012), Placentitis research (2009), Manifestations of equine herpesvirus-1
• 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)
• Nebraska Extension G1874 — The foaling mare (2008); Extension Horses — Horse foaling management guidelines (2020); University of Minnesota Extension — Caring for your mare (no vaccines in the first 60 days); 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

The Code is being revised, guidance on pregnant mares is revised as studies come in, and the sources above disagree in places, which this page says where they do. Check the current Code and labels before relying on a figure here; 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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