Failure Of Passive Transfer

What is failure of passive transfer? 

Failure of passive transfer (FPT) occurs when a new-born foal does not consume enough of the mares’ colostrum in the first 24-48 hours of life. The colostrum contains immunoglobulin antibodies (IgG and IgM) that are required for the majority of their immunologic protection against the pathogens they encounter in the first few days of life. The intake of this vital colostrum must occur before 48 hours (ideally in the first 8 hours) after birth as the cells required to transport the antibodies into the bloodstream are lost by the foal.

How do I know if my foal has FPT?

It is almost impossible to tell in the first few days of life if your foal has not ingested enough colostrum. The consequences of this will be seen as various recurrent infections in the first few weeks of life. Therefore what we recommend is that you have a vet perform a blood test on your foal in the first 12-24 hours of life and check the level of the IgG antibody. A reading of less than 200mg/dL indicates complete lack of transfer. A reading in-between 200 and 800 mg/dL indicates partial lack of transfer. Both readings require treatment. A normal reading is one above 800mg/dL.

What to do if my foal is diagnosed with FPT?

In cases where FPT is diagnosed after 12 hours, your foal will require an intravenous plasma transfusion containing the IgG antibody. These commercial sources of plasma are very safe as all donors are free of infectious disease. The amount of plasma given to an FPT foal will depend on the degree of failed transfer and the size of the foal, but is usually in the 2-4L range. The vet will test the blood after treatment to ensure an adequate level of antibodies.

What causes my foal to ingest inadequate colostrum?

Problems with the mare and problems with the foal can cause FPT. Examples of problems with the mare are early production of colostrum so it is expelled before birth, no milk production, poor quality colostrum production, lack of maternal cooperation and unfortunately mare death. With foals, premature birth of the foal can lead to problems such as inability to feed, or inability of the intestine to absorb the antibodies. In cases where you the know foal will not receive colostrum, ie mare death or early production, you can feed the foal colostrum from a previous colostrum bank or commercial frozen colostrum in the first 8 hours of life.

Ways to prevent FPT

As the prognosis for untreated FPT can be very poor, having ideas of how to minimise the risk are very useful. Having a colostrum bank or an alternative source of colostrum is a must. A colostrum bank is achieved by milking 250ml of colostrum off a mare after their foal has had its first suckle. If this is done from multiple mares, you will have enough for one foal. This colostrum can be stored at -4°C for up to 1 year. Other management strategies to undertake are observing all foaling’s to ensure normal parturition and early suckling, and to ensure a clean environment for foaling.

Artificial Insemination

Artificial Insemination (A.I) is a technique used to transfer semen from a stallion into the uterus of a mare during the correct stage of her oestrus cycle. A.I has become very popular in stud medicine for the advantages that it offers compare to natural covering (though not allowed in racing thoroughbreds), but, as much as it’s exciting breeding from your own mare, it’s important to understand how it works and the pros and cons before deciding to take this route.

What are the advantages of A.I

  • You can choose a stallion that is competing without interrupting his schedule
  • Allows you to choose the best stallion for your mare from all around the world and too far away to make natural covering viable
  • You can choose a stallion of which semen was frozen before his death or castration
  • Improve bloodlines for a rare breed also encouraging its geographical spread
  • Reduce risk of breeding injuries to both the mare and the stallion
  • More disease control by preventing skin contact such as in natural service and also by checking the stallion with swabs for Contagious Equine Metritis (CEM) and blood test for Equine Viral Arteritis (EVA) and Equine Infectious Anaemia (EIA) every year before the semen collection
  • Permits use of valuable stallions and mare with breeding problems
  • Allows mares to be bred at the best time for conception
  • Permits evaluation of semen at each collection and immediate recognition of minor changes in seminal quality.

 What are the disadvantages of A.I

  • Cost
  • AI with chilled or frozen semen generally has a lower conception rate (chance of producing an embryo) than natural covering
  • Risk to the mare when performing rectal examinations
  • Like for natural covering, AI does not always result in a live foal the following year.

Semen presentation

Management of the mare and timing of insemination will be determined by which semen is chosen (fresh, chilled or frozen) but it is also very important to check in which of the three ways the semen is preserved best and travels best for the specific stallion.

Fresh semen

Fresh semen is usually used on studs and only lasts outside the horse for short periods of time. It always has the highest fertility but mares and stallions need to be at the same location for insemination. Also fresh semen is usually the least expensive method, because requires no processing and less frequent veterinary checks.

Chilled semen

The semen gets refrigerated immediately after collection and transported in chiller packs either by post or manual collection, staying viable for 2-3 days. The conception rates are greater than for frozen semen. With chilled semen it’s important to find out which days of the week the stud collects from the stallion and how much notice you will have to give for them to collect and send the semen.

Frozen semen

After collection the semen is separated and added to a preservative. It is then frozen and stored below freezing, usually in dry ice. The semen can then be transported great distances in liquid nitrogen container and last for many years as long as it is kept frozen. Once arriving at its destination it can be defrosted, re-awakening the sperm and inseminated into the mare. Compared to chilled semen, the freezing and handling process slightly reduces the viability of the sperm and conception rates, therefore requires mares to be inseminated immediately before or after ovulation. However advantages are that breeders can use stallions which are still competing and the semen can be sent well in advance of the mare being in oestrus, avoiding the last minute delivery of chilled semen, which may not arrive on time.

Pre-breeding check

Prior to embarking on an A.I. program it is important the mare is examined to ensure that she is fit to breed and asses for factors that may reduce fertility. The pre-breeding check, best if  performed safely in stocks, consist of a physical examination to evaluate vulval conformation, a rectal examination to check the cervix for any abnormalities and ultrasound scan to look for uterine cysts and to see at what stage of the cycle the mare is. At this time we will also be able to take clitoral swabs and, if required by the stud, to do blood tests to check your mare is free of venereal disease.

Timing the insemination

Mares cycle between February and October (cycles at the beginning and the end of the season can be very irregular) and have a 21-22 day cycle, with oestrus (the receptive period) lasting 3-6 days. To have a successful insemination resulting in pregnancy it’s important to place the semen in the uterus when the mare cycles regularly and at the correct stage of the cycle, so when she is in season and close to ovulation. Signs of oestrus in the mare include tail raising, opening and closing of the vulva (winking), frequent posturing and urination and some may, also, become anxious, aggressive, sensitive around their flanks and reluctant to work, though can be difficult to detect and irregularly shown. Ultrasound scans of the ovaries and uterus allows detection of the stage of the cycle and, measuring the size of follicle, we can predict when the mare is coming close to ovulation and inject her with drugs that induce it. The best time to inseminate varies with the type of semen used: for fresh and chilled, AI need to be done within 12-24 hours of ovulation whereas for frozen AI it needs to be done within 6 hours of ovulation, which means a greater number of scans are required both during day and night.

Pregnancy Diagnosis

The most appropriate time to determine the pregnancy is between days 14 and 16 following ovulation through a transrectal ultrasound. At this time it’s very important to check for multiple pregnancies and, if necessary, deal with it before the embryo becomes attached to the lining of the uterus and makes it difficult to “squash” the twin.

14-16 days embryonic vesicle

A further scan around 28 days to check the normal development by identification of the foal’s heartbeat is advised. This also reduces the risk of missing detection of a twin pregnancy. If the mare is not pregnant then she should go back in season again allowing the program to be repeated, hopefully, with a more favourable outcome.

2-3 month pregnancy scan

Fostering Foals

In the sad event that a mare is unable to nurse her own foal it may be necessary to foster the foal onto a mare that is not its natural mother. This process requires very careful planning and should be arranged as soon as possible and before the foal is 3 weeks of age.

The foster mare will usually be a mare which has lost her own foal, but should also be one who is suitable. The mare must be vaccinated, healthy, have a quiet temperament, be well handled and ideally have experience in mothering foals. In addition, the mare must be producing the volume of milk necessary to nourish the foster foal. Mares for fostering are often advertised on social media sites or via The Foaling Bank.

Foals are born without natural protection from infection. At birth they receive this via colostrum, the first milk, which they must ingest within the first 18 hours of life. To be suitable for fostering, a foal should have received adequate colostrum, either from their own dam or from a donor source. This ‘transfer of passive immunity’ can be checked by taking a blood test from the foal at 24 hours to measure IgG levels, which should be over 800mg/dl. If this has not been achieved a plasma transfusion should be given. Foals suitable for fostering should also be strong, able to stand unassisted and to suck well.

Preparation of the mare for fostering is a delicate process. If the mare has recently lost her own foal she should be left in a stable with it and, if possible the placenta should be kept. Once the foal for fostering is ready the dead foal should be gently removed from the mare and skinned. The skin of the dead foal can then be used as a coat for the foster foal and, if available, the foal can be rubbed with the placenta, to transfer the dead foal’s smell.

The mare and foal should be introduced to each other in a large, clean stable. The mare should be deeply sedated and held using a bridle. It is helpful if the mare’s bag is not overfull, as this may make sucking painful for the mare. In addition, the foal should be hungry when first presented, to encourage sucking. The mare should be positioned in a corner of the stable and the foal introduced at her shoulder so that she can see and smell the new foal. The mare must be closely monitored; nickering and ‘talking’ to the foal would be an excellent reaction, but she will often behave aggressively and require further restraint to allow the foal to approach. The mare and foal should not be left alone at this stage, as some mares will wait for an unguarded opportunity to show aggression. It is helpful to allow the foal to move around the box at some distance from the mare to allow her to get used to the foal. Mare milk replacer or milk pellets should be available to supplement the foal.

It may take days before the fostering process is complete and in some cases an alternative foster mare may be required. It is vital that the mare and foal are not left unattended until there is complete confidence that the process has been successful. Fostering can be a very satisfying process, making the best out of a less than ideal situation. Orphaned foals that are raised on foster mares are easier to manage, healthier and better developed physically and mentally than hand-reared foals. However, if there is no mare available or the foal risks injury from an aggressive mare, then hand rearing an orphaned foal may be the only option.


This is often a very stressful time for the owner, so here is a bullet point article to lead you through the whole process of foaling and making sure there are as few complications as possible. It will also help you to identify problems early and call in the cavalry (That’s us!)


1st stage labour:
This can last about 1-4 hrs, during which time the mare may become restless, start to sweat and show mild colic symptoms including flank watching. The rupture of the chorioallantois occurs near the end of the 1st stage of labour which will result in the release of allantoic fluid which will gush out of the vulva.

2nd stage labour:
The mare is usually laterally recumbent by now and will experience strong abdominal contractions. Within a few minutes the unruptured amniotic sac should appear at the vulva. This is WHITE in colour. If the membranes are RED in colour this indicates that the chorioallantois has not ruptured (RED BAG). This indicates premature placental separation and is an emergency. The membranes should be ruptured immediately and the foal delivered, even if this has to be started before the cavalry (That’s us again!) arrives.
Stage 2 should take no longer than twenty minutes until the foal is delivered. If the mare does not seem to be getting on with it during this period then you should call for veterinary assistance immediately.
When the foal is delivered the mare often lays down for a period of time. This should be encouraged as it gives time for blood from the placenta to flow into the foal before it detaches. The foal will often break its own umbilicus when it struggles to get up.

3rd stage labour:
This is the expulsion of the placenta after foaling. This should be complete within three hours.

Care of the newborn foal
The foal should be up and sucking within the first 2-4 hrs of birth. If not sucking by then it is important to get veterinary attention ASAP.
The foal’s digestive tract absorbs antibodies from the mare’s colostrum best in the first 8hrs of life. After this period the amount absorbed diminishes until 32hrs when no more can be absorbed. A sensible precaution would be to blood sample the foal about 18hrs after birth to see what its antibody status is and if low then plasma can be given intravenously to boost immunity. This is not without risk and so it is important to blood sample first to see if required.
The foal is at increased risk of low antibody transmission if it doesn’t suck well in the first 18hrs or if the mother is a maiden mare with poor colostral quality, or runs milk for a period of time before foaling.
The foal usually passes meconium (first faeces) in the first 2hrs of life. It is important this happens as if it doesn’t then it will become constipated and not suck. This meconium impaction leads to colic if not resolved quickly. Phosphate enemas are usually successful particularly if given early.
The foal’s navel needs treating soon after birth with a suitable product (iodine based) and ideally repeated twice a day for a couple of days.
The foal may have in-turned eyelids (entropian) which should be looked for in the newborn and if present corrected.
If any tendon contraction or laxity is present then speak to the vet as splints may need to be used and other techniques.

Care of the mare post foaling
Most mares pass the placenta within 3hrs of foaling. If this has not happened by 6 hours then veterinary assistance should be sought as the mare soon becomes toxic if the placenta is not removed. Injectable oxytocin often helps coupled with antibiotics / antiendotoxins.
Once the placenta has been removed we would recommend copious flushing of the uterus with saline until the fluid runs clear followed by a few days of oral antibiotics. Never be tempted to pull hard on the placenta as it may tear leaving some inside which leads to uterine infections.
It is important to check the placenta to ensure it is complete and that no evidence of infection is present. It looks a little like a pair of pyjama bottoms. If in doubt as to whether all is present then it should weigh about 10% of the foal weight.
If the mare becomes unwell over the next 72hrs then it important to re-examine her as internal bleeding is possible, as are uterine tears or other problems.

It is worth stressing that all these problems are uncommon and most foaling goes without hitch. It is always worth getting us out to check the mare and foal between 12 and 24hrs after foaling even if everything goes well. If you have any concerns then err on the side of caution and call us out sooner rather than later.

Thinking Of Putting Your Mare In Foal?

Whilst the thought of having a lovely home bred foal which in time matures into your perfect riding horse is a lovely idea this may not be the reality. The decision to put your mare in foal needs much planning, time and effort.

There are four main questions that anyone considering breeding from a particular mare should ask:

  • Is she suitable for breeding? Conformation, temperament and performance are key. A mare shouldn’t be bred from simply because she is no longer suitable for any other purpose!
  • Are suitable facilities/expertise available? Including facilities not just for the in-foal mare but also for foaling, for the new born foal and in time for a growing youngster. Do you have the experience to deal with a foaling mare and potential problems or would she be better at stud?
  • Can I afford it? Stud fees, livery charges and routine and unexpected veterinary bills can add up to a substantial sum and there is no guarantee that a healthy foal will be produced/the foal will mature into a quality horse. Breeding can be a risky business for both mare and foal.
  • What are my plans for the foal? Are you breeding to sell or breeding for yourself? What will your circumstances be in 4 years time when the foal is grown up and ready for riding?

Having considered your options and decided to go ahead your next decision is which stallion to use. This is influenced by your mare in terms of conformation and abilities but also what the foal’s intended use is. Considerations include conformation, soundness, performance, temperament, fertility, cost and terms of the stud fee and availability of chilled/frozen semen.

So you have a suitable mare and have found the ideal stallion to complement her, what next?

Your vet will need to come out and perform some pre-breeding checks prior to commencing the process of actually getting her in foal to ensure the best chance of success. These include;

  • Swabs and blood tests to check for specific bacterial and viral diseases, namely Contagious Equine Metritis (CEM) and Equine Viral Arteritis (EVA) – It is worth getting these done early in the season to save time later on.
  • Gynaecological examination to inspect the mare’s vulva, vagina and cervix.
  • Ultrasound examination per rectum to ensure both the uterus and ovaries are normal and to check the mares stage of the oestrus cycle. Uterine swabs can be taken at this stage if there is any concern over infection/previous fertility issues to allow appropriate treatment.

If your mare is not in season at the first scan then she will be given drugs to bring her in to season. Once she is in season your vet will need to visit regularly to perform repeated ultrasound scans to ensure that she is inseminated at exactly the right time to optimise chances of pregnancy. If you are using frozen semen the number of visits and scans is much increased due to poorer semen quality. It is essential that you have adequate facilities to restrain your mare for these examinations, some mares need sedation for everyone’s safety.

Remember to liaise with the stud and ensure that the semen is available and delivered when requested accompanied by the correct paperwork – contact the stud with plenty of notice!

After insemination we will visit again to ensure that all has gone to plan, that the mare has ovulated and there is no adverse reaction to the semen. Some mares will need further treatment at this stage including further injections and flushing of the uterus.

Assuming all goes to plan then pregnancy diagnosis will be performed between 15-18 days and at 30 days where hopefully we will identify a heartbeat! Unfortunately many mares (especially older ones) won’t get in foal first time so be prepared to go through it all again!

In a nutshell consider your options carefully, contact us in plenty of time to discuss your plans, be aware that your mare will need several visits prior to insemination and then keep your fingers crossed for a happy bouncing foal!


Equine Abortion

An abortion is when the foetus dies and is expelled before 10 months of pregnancy. The foal is stillborn if it survives to 10 months but is dead at birth.

What to do if your mare aborts;

  • Call the practice to arrange for the mare to be checked and samples of the foetus to be taken.
  • Isolate aborting mare immediately and collect aborted foetus and membranes in leak-proof containers. These material must be handled hygienically.
  • If the mare has aborted in the field, corner off any contaminated ground.
  • Stop movement off the stud/yard pending diagnosis of the cause of the abortion. Do not allow any pregnant mare onto the stud until EHV-1 has been excluded.
  • Disinfect and destroy contaminated bedding, and clean and disinfect premises, equipment and vehicles used for horse transport.

Signs of impending abortion;

  • Unexpected enlargement of the udder, dripping or running milk. Especially before 320 days of pregnancy.
  • Vaginal discharge; mucous staining in tail.
  • Coming into season.
Infectious causes of abortion

Equine Herpesviruses 1 and 4 (EHV-1 & EHV-4)

A majority of mares will be dormantly infected with EHV. The infection is likely to re-awaken at times of stress. Abortions caused by EHV happen quickly and can spread rapidly through a herd; they are sometimes known as “abortion storms”.

Steps to prevent and minimise transmission of the disease;

  • Vaccinate mares (a course a three injection at the 5th, 7th and 9th month of pregnancy).
  • Minimise stress in late pregnancy. Try not to move mares during last month of pregnancy.
  • Minimise contact between mares in late pregnancy and avoid new introduction – especially younger horses (eg filly out of training).

Equine Viral Arteritis

This is a notifiable disease but is seen more commonly in continental Europe. Transmission can occur at teasing mating, insemination and contact with aborted material. Along with abortion, the mare may show conjunctivitis, neurological signs and peripheral oedema (eg swelling of lower limbs).

Although there is a vaccine available it is usually reserved for stallions. It is recommended that mares are regularly screened for EVA each year; this is done with a blood test. Stallions and semen should also be declared EVA free before use.

Bacterial and Fungal Infections

This can occur at any point from 3 months of pregnancy. They can be treated, so please call the vet if there are signs of vaginal discharge, matting of the tail or rubbing/itching of the behind. However, prognosis can be guarded in these cases.

Non-infectious causes of abortion

Non-infectious causes are the most common reasons for mares aborting. Some of which are, unfortunately, unpreventable.

Congenital and developmental abnormalities

Umbilical cord abnormalities account for approximately a third of all abortion within the UK. Excessively long or twisted cords can result in a lack of blood supply to the foetus, resulting in the death of the foal and subsequent abortion.

Twin pregnancy

The conception of twins present a problem for mares as they do not have the uterine capacity to support the normal development of more than one healthy foetus. If twins become established one or both are likely to die in the uterus resulting, usually, in an abortion or premature foaling. Not only is the pregnancy wasted, the health of the mare may also be compromised.

Natural reduction has a limited efficiency at reducing twin pregnancies, therefore it is very important to recognise twins at the earliest stage possible and carry out effective treatment to achieve a healthy singleton pregnancy.

Best way to ensure a singleton pregnancy is to scan the mare between 14 to 18 days after ovulation. This is before the embryo has time to be fixed within the uterus. One of the pregnancies can be manipulated and crushed, leaving only one pregnancy. It is possible to reduce a twin pregnancy after this stage but they are generally more difficult and carrier a greater risk of losing the remaining pregnancy.