Caring for a pregnant mare (Australia): the southern season, the vaccines, 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 feed, her exercise, her vaccinations 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. In Australia the calendar runs the other way to the books written in the north: the Thoroughbred covering season opens on 1 September, every Thoroughbred has its birthday on 1 August, and the risks that come with the seasons, from caterpillars in autumn to heat in summer, fall in months a northern guide does not expect. This page takes the pregnancy stage by stage, with what the veterinary sources say at each, then the complications worth knowing by their signs.

The pregnancy at a glance

The dates of each step, from the day she was covered, are on the foaling date calculator, which also gives the due date and the normal window around it. In outline, with the Australian vaccination program the University of Melbourne's prescribing guidelines give for a mare already vaccinated:

A season that runs the other way

For Thoroughbreds the calendar is set by the Rules of the Australian Stud Book. The covering season runs from 1 September to 31 May, the foaling season from 1 July to 30 June, and every Thoroughbred turns a year older on 1 August, the official birthday: a foal becomes a yearling on the first 1 August after its birth, though one that is 31 days old or less that day, from a mare first covered within the season, does not have to. The rule that matters at the covering is the other exception. A foal whose dam was first covered in June, July or August, outside the season, is counted as a yearling from the day it is born, whenever that is. And a Thoroughbred is bred by natural service only: the Stud Book does not accept the foal of any form of artificial breeding.

At the usual 340 days, a mare covered on 1 September is due at the start of the following August, and one covered on 15 December around 20 November; the normal window runs from 320 to 370 days, which the calculator shows for any date. Harness racing keeps a similar year: the Australian Trotting Stud Book's breeding season runs from 1 September to 31 August.

Two risks follow from the calendar that a northern guide puts in other months, or leaves out. The caterpillars that cause equine amnionitis and foetal loss are most dangerous to pregnant mares from March to June, by AgriFutures' reckoning, which for a mare covered in spring is the middle of her pregnancy (below, under Complications). And a mare covered in January is due between early December and early January, and foals in the heat.

Heat

None of the sources we found sets rules for a pregnant mare in hot weather, so the general ones apply. In the ACT one of them is mandatory: the code requires that horses have access to appropriate and sufficient shade and shelter at all times. Agriculture Victoria advises planning for days over 36 °C in dry heat, or less when it is humid, with shade and ample cool water, checking animals through the day, and moving or transporting them only in the cooler hours; it notes of livestock that heat stress can affect reproduction. In a horse, look for heavy sweating and a mare off her feed; it advises cooling one by hosing with cool water from the feet up, and scraping the water off afterwards unless there is a breeze.

Feeding her through the pregnancy

For most of the pregnancy, a mare needs no more than she did before she was covered. 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", to about 23% above maintenance in month eleven. Agriculture Victoria's feed-budget table gives the figures in megajoules of digestible energy. For a 500 kg mare:

The table shows where the real rise comes: after the foaling, not before it. The ACT's code says the same, putting a lactating mare's needs at about 70% more energy than those of a horse not in work. In the pregnancy, the last months are 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 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.

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.

Her condition

Not too thin, not too fat, and check which scale a number is on. 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. Those are on the 1 to 9 scale. Agriculture Victoria scores condition from 0, very poor, to 5, very fat, so a broodmare's 6 does not exist on it; on that scale, the ACT's code and Western Australia's standards keep every horse between 2 and 4. On why condition matters, the sources 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. Western Australia's standards note that pregnant and lactating mares should be fed appropriately and closely monitored for loss of condition. 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.
• Calcium on tropical pasture. If she grazes kikuyu or setaria, read the feeding guide on big head, and ask your vet how much calcium she needs.

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.

Competition and riding schools do set dates. At FEI events, the FEI's code of conduct for the welfare of the horse says mares must not compete after their fourth month of pregnancy or with a foal at foot. In Western Australia, a riding school or horse hire establishment must not use a mare more than six months pregnant, or one lactating in the first three months after foaling, unless on veterinary advice.

Vaccinations

The University of Melbourne's Australian Veterinary Prescribing Guidelines list the vaccines available for horses here as tetanus, strangles, Hendra virus, equine herpesviruses 1 and 4, Salmonella and rotavirus; there is no influenza vaccine on the list. Their protocol for a breeding mare that has been vaccinated before:

For a mare with no record, or an unknown one, the same guidelines give longer courses: two tetanus doses 4 to 6 weeks apart then one 4 to 6 weeks before foaling, Salmonella no later than 10 and then 6 weeks before foaling, and rotavirus in the 8th, 9th and 10th months. Zoetis's Equivac 2in1 covers tetanus and strangles in one injection.

The EHV vaccine. Zoetis's Duvaxyn EHV 1,4 is labelled for respiratory disease and "as an aid in the control of EHV-1 abortion", and its label has a pregnant mare that has been primed vaccinated in the 5th, 7th and 9th months of pregnancy. It states that the vaccine is safe for pregnant mares, and that a vaccinated mare may still abort. The AAEP's guidelines note that some vets add a dose at three months.

Hendra. Zoetis states that Equivac HeV has been found safe for pregnant mares, but not to be given in the first six weeks after conception or the two weeks before the expected foaling; the University of Melbourne's guidelines, in the table above, put the first window at 45 days. Every dose goes into the online registry. Foals of vaccinated mares start their own course at six months. The ACT's code adds advice for every horse: feed and water containers should never be placed under trees that flying foxes are likely to frequent.

Early 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 Australian vaccination guide has the rest of the program.

Worming

Worming is safer than many owners think. Merck says "most anthelmintics are safe for use throughout pregnancy", provided the warnings on the label are followed, and the label is where the exceptions are: on an American fenbendazole label, the drug was tested in mares at every stage of pregnancy with no effect on reproduction, but its five-day, 10 mg/kg larvicidal (large strongyle) course "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.

The 2025 Australian guidelines for equine internal parasite management treat adult horses by their faecal egg counts and say nothing particular about pregnant mares. Around the foaling, the international 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 worm the mare after the foaling instead, from within 48 hours (another Merck chapter) to about a week (Colorado State). For the foal, the Australian Veterinary Association advises no wormer before two months of age unless threadworm is a concern, then treatments at two and five months. Which your vet follows is their call; the Australian worming guide explains the egg counts and the resistance behind them.

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. In Western Australia, only a vet may perform a Caslick's procedure. EquiDiary's pregnancy plan offers the opening as a step of its own.

Getting ready to foal

The place. A box of at least 4.3 × 4.3 m (14 × 14 ft), say Penn State Extension, Nebraska Extension and Merck, which finds a double box of 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. Western Australia's standards ask for a safe and suitable foaling environment for a mare in the last month of pregnancy, and extra space for mares in foal. Wherever it is, it is where she should already be living: the calculator dates the move.

Watching her. In the ACT, mares in late pregnancy must be inspected at least twice daily, a mandatory standard; Western Australia's guidelines say a mare in her last month may need checking more than once a day, and often enough to catch a difficult foaling early. Western Australia also forbids tethering or hobbling a mare more than 40 weeks pregnant, or with a foal at foot.

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 bandage, 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 torch, a head collar and a lead rope. When labour 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 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 ACT's code lists a pregnant mare straining for more than 30 minutes without foaling among the conditions that may need prompt veterinary attention. The veterinary sources above call sooner, and theirs is the limit to keep.

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 straight 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 tread 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 droppings (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. The ACT's code and Western Australia's standards ask the same of whoever is there: watch the mare until the placenta has passed, within three hours, and the foal for its first 24, until it has passed the meconium, urinated, sucked and taken in its colostrum.

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. For a Thoroughbred, the Stud Book's advice is to start the foal's identification in its first hour, when the hair whorls are easiest to see.

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 foal's papers

• Thoroughbreds. A mare with a live foal needs a Mare Return lodged with the Australian Stud Book within 30 days of foaling. The Stud Book may extend that to 120 days, with a late fee, and past it reserves the right not to accept the foal. A mare that lost her foal, or missed, is returned within 12 months of her last service. The foal should be freeze-branded in time for the brand to be readable by 31 March of its first year, and is microchipped and DNA-sampled by a vet the Stud Book authorises.
• Standardbreds. The Australian Trotting Stud Book Regulations require the foaling to be notified to Harness Racing Australia on its form within 21 days.
• Western Australia. Every horse must carry a registered brand or an approved identifier, which can be a breed society's microchip, before six months of age in the South West Land Division, or 18 months elsewhere, or before it is moved if that is sooner.

The Australian papers guide covers the property registration and movement rules every horse lives under. When the foal is weaned, the ACT's code says not before four months and before nine; Western Australia's standards forbid weaning before four months unless on veterinary advice, and its guidelines advise not before six.

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 draught 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). In Australia, add the caterpillars, below. Often there is no warning at all. If it happens:

• Keep the foetus and the whole placenta and get them to your vet or the diagnostic laboratory, kept cool in an esky with ice packs (the AAEP) but never frozen (Merck). Only a laboratory can say why, and the answer decides what the other mares need: even two large Kentucky series of aborted foetuses, 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 paddock (the University of Kentucky).
• Some causes must be reported. Each state and territory sets its own list under its own law. Western Australia's reportable diseases and the Northern Territory's notifiable ones both include equine herpesvirus-1, equine arteritis, equine infectious anaemia and contagious equine metritis (Taylorella equigenitalis), and in both, an owner who knows or suspects one must report it, as must the vet. The Emergency Animal Disease hotline, day and night, is 1800 675 888.

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 foetus 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.

Equine amnionitis and foetal loss: the caterpillars

An Australian form of abortion in mid- to late-pregnancy. It was first identified in a series of abortions in Thoroughbred and Quarter Horse mares in the Hunter Valley between March and November 2004, and the cause was found to be the mares eating processionary caterpillars, Ochrogaster lunifer, the larvae of the bag-shelter moth. In experiments, mid-pregnancy mares given whole caterpillars or only their shed skins aborted, with few signs beforehand; a later study found that early pregnancies can be lost too. The caterpillars' fine hairs are the problem: fragments were found in the uterus of exposed mares, and the researchers judge that the hairs most likely carry bacteria in with them. Some foals are not aborted but born premature, weak and underdeveloped (AgriFutures). The Australian Veterinary Association reports that the caterpillar may account for up to a third of abortions in the Thoroughbred industry.

The caterpillars live together in silk nests over spring, summer and autumn, then the last of them leave to pupate in the ground, and their hairs are found in the nests, the shed skins and the pupation sites. The hairs travel on the wind: a 2019 study judged the risk of exposure high within 100 m of caterpillar activity. AgriFutures puts the highest risk for pregnant mares in March to June, when the caterpillars are on the move, and advises:

• inspecting tree trunks and branches for egg masses in October to December, and removing them, and the nests in January to March;
• disposing of them in a deep hole, burial being better than burning;
• moving pregnant mares off paddocks with nests where that is practical, though with nests so widespread, removing the nests is the more practical way;
• talking to your vet about ultrasound checks and targeted treatment for mares in high-risk paddocks.

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, 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 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% (20 of 21) 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 oedema, 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 15 to 20 minutes after the waters break, 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 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, endotoxaemia and laminitis (Merck). Do not pull it; tie it up and call the vet. Western Australia's guidelines, too, call for urgent veterinary advice when the placenta fails to pass.

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.

Hyperlipaemia 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.

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 in Australia — the 2-in-1, Hendra, and why there is no flu booster
• Horse worming in Australia — egg counts, resistance, and seasons that run the other way
• Horse papers in Australia — property registration, brands and microchips, and the state borders
• Horse feeding plan in Australia — the state codes, condition score 2, and the pastures that work against you

Sources

• Racing Australia — Rules of the Australian Stud Book (1 March 2019, the current version: official age, covering and foaling seasons, natural service, Mare Returns rules 4.6–4.11, branding rule 5.3, identification) and Australian Stud Book rules and services
• Harness Racing Australia — Australian Trotting Stud Book Regulations (breeding season; notification of foaling, regulations 16–17)
• University of Melbourne — Australian Veterinary Prescribing Guidelines, equine immunisation (vaccines available; Figure 16.2, the breeding mare)
• Zoetis Australia product information: Duvaxyn EHV 1,4, Equivac 2in1 and Equivac HeV
• Australian Veterinary Association — Hendra virus policy, Use of anthelmintics in equine practice and Vet Voice, Hairy caterpillars harm horses (2018)
• AgriFutures Australia — Keep an eye out for caterpillar eggs and nests during high-risk period (2024)
• Equine amnionitis and foetal loss: the case definition, 2009, abortion after experimental exposure, 2012, the 2004 Hunter Valley cases, 2013, early pregnancy, 2013, hairs in the uterus, 2014, where the hairs are, 2016, airborne dispersal, 2019
• ACT — Animal Welfare (Welfare of Horses in the ACT) Mandatory Code of Practice 2024 (S2.4, S6.5, G4.16, G4.17, G11, section 16)
• WA DPIRD — Standards and Guidelines for the Health and Welfare of Horses in Western Australia (G2.3, S14.3, S15.4, S15.6, G15.4–G15.9, S23.2)
• Reporting: WA DPIRD — Reportable animal diseases and NT Government — Notifiable diseases in animals; WA DPIRD — Identification and movement of horses and donkeys
• Agriculture Victoria — Feed requirements of horses (Table 1), Condition scoring and weight estimation and Caring for animals during extreme heat
• Australian Equine Parasitology Advisory Panel — Australian guidelines for equine internal parasite management, Australian Veterinary Journal, 2025
• FEI — 2026 Veterinary Regulations (code of conduct for the welfare of the horse: pregnant and recently foaled mares)
• Merck Veterinary Manual — Nutritional requirements of horses (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); Retained fetal membranes; Neonatal encephalopathy (red bag); Hyperlipemia; Nutritional myopathies (selenium); Dental, coat and hoof care
• AAEP — 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; Equine alphaherpesvirus vaccination guidelines (2025: the extra dose at three months); Internal parasite control guidelines (worming at foaling)
• 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 — 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; worming: 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; hyperlipaemia: 1992; rebreeding: 2012; tears: 2025

Guidance on pregnant mares is revised as studies come in, and stud book rules, labels and state codes change; check the current version before relying on any detail here, and confirm the program with your vet.

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

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