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Fragile Foal Syndrome

By Amelia Campbell-Horne

With breeding, so many things can go wrong, so any risk that can be eliminated should be! Fragile Foal Syndrome (FFS) is one such risk that can be easily avoided. In this article, HQ chats with Dr Mareli Smalberger, South Africa’s local FFS expert, to help us understand how we can eliminate this risk in our breeding programmes.

HQ: Please tell us a little about yourself.

Dr Mareli:  I have done dressage pretty much my whole life, competing up to FEI Small Tour and have always wanted to be a vet. I really struggled to get into vet school, so I did a degree in Animal Science and then my Masters in Animal Nutrition. Halfway through my Masters, I was accepted into vet school (Onderstepoort), so then I did the two degrees simultaneously for two years and graduated as a vet in 2020. I sold my horse while I did the two degrees simultaneously because there wasn’t time to eat or sleep… But I have taken up riding again since graduating.

HQ: Wow, where there’s a will, there’s a way! So, on to Fragile Foal Syndrome (FFS), you did your research project on the topic?

Dr Mareli: Yes, my research project was titled ‘The Significance of Fragile Foal Syndrome in South Africa’. I attended the SAEVA (South African Equine Veterinary Association) Congress in 2019 and asked a question about FFS, and noone had any answers. I then realised it was one of our research project options, and since no recent research had been done, I pursued it. The idea was to develop a local genetic test and establish whether the condition was present or not in the country. There are Warmblood stallions who are offspring of confirmed carriers, and semen of confirmed carrier stallions is available to South African breeders, so there was potential for the condition to be present locally, but we were completely in the dark. My other reason for choosing this research topic was because of the heartbreak this genetic condition can cause and how easily such heartache can be avoided!

HQ: What is Fragile Foal Syndrome?

Dr Mareli: It is a genetic condition that affects connective tissue. Essentially the collagen linkage throughout the foal’s entire body is abnormal, which means they don’t have normal skin and joints. These foals have thin skin, severe bruising or lacerations, hyperextensible joints, and sometimes skeletal abnormalities. If they are born alive, it is impossible for them to survive, and they would need to be euthanised within a few hours of birth. These foals are often aborted late or stillborn. However, Fragile Foal Syndrome is a recessive genetic disorder, so with careful breeding, having affected foals can easily be avoided.

HQ: So, how did you go about your research?

Dr Mareli: In order to develop a genetic test, we had to verify the Warmblood horse genome and the location of the mutation with DNA samples from a known non-carrier and two known carriers. We also sequenced DNA from 18 Warmbloods who had confirmed carriers in their parentage to rule out any other mutations in that area of the gene. Once we knew the test worked, we tested a larger population of 110 Warmbloods that consisted of 82 Warmblood stallions with no suspicion of FFS in their pedigree and 28 horses with known or suspected carriers in their parentage. From this data, we drew our conclusions.

HQ: And Warmbloods were used because this is the breed in which most cases have been identified? How did you find the horses for the study?

Dr Mareli: I focused my research on Warmbloods because the condition was first discovered in Warmbloods, and it is the breed with the highest incidence of FFS worldwide. However, it has since been discovered in several other breeds. The horses were all from an anonymised database. All I knew was that the horses were Warmbloods in South Africa and whether they were mares, stallions or geldings; had dressage, jumping or dual-purpose bloodlines; if they were suspected to be carriers based on their parentage; and whether they were imported or bred locally.

HQ: So, what were the key findings?

Dr Mareli:  We found that 19% of the horses tested were carriers! Since the study tested a targeted population to verify the genetic test and establish the presence of FFS in South Africa, it was too small to draw conclusions from for the general Warmblood population. Our study was also skewed because 28 of the horses were suspected to be carriers based on their pedigree, and 53% of those were carriers. Of the horses with no suspicion of FFS in their pedigree, we found that 7% of those were carriers, one of which was locally bred, meaning the gene has already been carried to our local breeding population.

HQ: Were there any other significant findings?

Dr Mareli: Well, the trends in this South African study matched international trends as 24% of the horses with dressage breeding that we tested were carriers, while only 15% of those with jumping breeding were carriers and 22% for the dual-purpose pedigrees. In Europe, there is a similarly higher incidence in dressage breeding, especially in the Hanoverians. This is because there are really prolific breeding stallions that have won Hanoverian stallion of the year that were carriers. Hence, they obviously disseminated the gene into the breeding population quite extensively. FFS gene seems to be in close relation to genes encoding for increased limb flexibility, so, especially in dressage this increased flexibility leads to more impressive paces and makes these genetics sought after.

HQ: Is there a way to find out if an international breeding stallion is a carrier?

Dr Mareli: Most stallion directorates will state whether a stallion is a carrier of FFS or not since there has been large-scale testing of stallions (mandatory and voluntary) overseas. If you are interested in a stallion for breeding, just check his status and make your decision based on that. It would be great if we could have similar transparency for our local stallions in future.

HQ: As I understand it, it is a recessive gene, so the only time a risk factor comes in is when you are breeding two carriers?

Dr Mareli: Yes, that is correct. So, if you breed a carrier to a non-carrier, you have no risk of having an affected foal. However, there is a 50% chance of breeding a carrier. If you breed two carriers to each other, then you have a 25% chance of having an affected foal, and these foals are unable to survive.

HQ: Do most of these affected foals go to full term?

Dr Mareli: Findings have shown that late abortions are characteristic of FFS foals, as well as stillbirths or weak foals born alive. There is also a high likelihood of dystocia (difficult births) as the foals have hyperextensible joints, and some have skeletal malformations as well. We do believe that instances of foals with FFS have been under-reported; we think a lot of these affected foals were born long ago, and where they were severely affected, they were just written off as malformed with no consideration of a potential genetic cause. Similarly, with late abortions (25% of which have no known cause), the foal might not look affected, and no further tests are done. There is still a lot of research required as although the gene was discovered in 2011, the first commercial test was available in 2013, and the first affected foal was described in 2015 – public awareness only began to grow around 2018!

HQ: So, although we have not had any known cases of affected foals born in South Africa (and we hope never to), there are still occurrences of late-term abortions and non-viable foals, so your recommendation is to have the test done in these instances?

Dr Mareli: If the foal is being sent for a post-mortem, you can specifically request the test. It is an inexpensive test, and then at least you know. Also, if you have a mare that has aborted in the past or given birth to a foal that you suspect might have been affected, you can have the mare tested for whether she carries the FFS gene.

HQ: I believe the test is R520, and you send a DNA sample?

Dr Mareli: Yes, R520, unless your horse is already on the Veterinary Genetics Laboratory DNA database, then it would be R320.00. For example, stallions (and mares) that have had DNA testing done for the SA Warmblood Horse Society would pay the reduced rate if the sample on the system is still viable. Either EDTA blood samples or hair root samples are acceptable.

HQ: Should you avoid breeding with a known carrier?

Dr Mareli: Not at all! Some of the best stallions in the world are carriers. It is important to remember that a horse that is a carrier of the FFS gene is physically normal and can make a fantastic competition horse. The only time you do need to be careful is when breeding two carriers. In essence, all you need to do is test your mares and stallions, and you can avoid having an affected foal.

HQ: So, what’s next with your research?

Dr Mareli: I would like to test a larger sample of the South African Warmblood population so we have more robust data that will be representative of the entire population. We might have a natural protective mechanism in our population due to our history of breeding with Thoroughbreds, who have a much lower incidence of FFS, but we can’t establish this until we have enough information. I would also like to check the occurrence in other breeds in South Africa where carriers have been identified, such as the Thoroughbreds, Appaloosas, Irish Sport Horses etc. The research possibilities are endless! [end box]

If you do decide to get your horse tested, please be sure to CC: when you send your request to The data will be kept completely anonymous, but if you are willing to provide a full pedigree, this will greatly assist in the depth of research that can be achieved!

And if you would like to learn more, you can check out Dr Mareli Smalberger’s Webinar on the SAWHS Youtube channel – ‘Fragile foal syndrome’.