ICSI has become an increasingly important tool in modern equine reproduction. But for breeders and horse owners, one question remains particularly important: does the way an embryo is produced affect the health of the foal? Two studies published in 2026 provide reassuring results.
Intracytoplasmic sperm injection (ICSI) allows a single sperm cell to be injected directly into an oocyte to create an embryo. Combined with ovum pick-up (OPU) and embryo transfer, the technique has opened new possibilities for sport horse breeding and for making the most of valuable genetics.
But with any advanced reproductive technology, it is reasonable to ask whether the process could influence the developing foal. Could ICSI affect birth weight, the ability to stand and nurse, early neonatal adaptation or placental development?
Two recent studies specifically investigated these questions. Although they examined different groups of foals and different parameters, their overall message is remarkably consistent:
Current evidence does not indicate that ICSI itself negatively affects the early health or adaptation of foals.
What did the first study investigate?
The study “Does the Reproductive Technique Affect Neonatal Health Parameters in Foals?” was published in Reproduction in Domestic Animals in March 2026.
Researchers analysed data from 102 foalings at two commercial breeding farms. The foals were produced using artificial insemination (AI), conventional embryo transfer (ET) or intracytoplasmic sperm injection (ICSI).
The researchers recorded several indicators of neonatal adaptation, including birth weight, time to sternal recumbency, time to stand, time to nurse and time to meconium elimination.
The result was clear: no significant differences were found between AI, ET and ICSI foals for any of the neonatal parameters evaluated.
In other words, the ICSI foals in this study did not show evidence of poorer early neonatal adaptation compared with foals produced through artificial insemination or conventional embryo transfer.
Source – Study 1: Alonso MA et al. (2026), Does the Reproductive Technique Affect Neonatal Health Parameters in Foals?, Reproduction in Domestic Animals, 61(3), e70192.
What does the second study add?
The second study, “The effects of ICSI on foal health and placental parameters”, looked at the question from a slightly different perspective.
The researchers evaluated 90 Warmblood foals born between 2020 and 2024. The foals were divided into three groups according to how the pregnancy was established: artificial insemination, embryo flush and transfer, or OPU-ICSI followed by embryo transfer.
This study went beyond basic neonatal observations. Researchers assessed foal and placental measurements, colostrum quality, time to first suckle, time to stand, meconium passage, passive transfer of immunity and placental expulsion.
Once again, the overall result was reassuring: foals from all three reproductive groups appeared clinically healthy and were broadly comparable.
No significant differences were found in foal body measurements. Placental measurements were also largely similar between the groups.
Source – Study 2: Van den Branden E et al. (2026), The effects of ICSI on foal health and placental parameters, Journal of Equine Veterinary Science, 164, 105982.
Were there any differences in the ICSI foals?
Yes – and this is where the details matter.
The second study found that ICSI foals took longer to begin suckling than the embryo-flush group and longer to pass meconium than the AI group.
However, the researchers did not interpret these findings as evidence of compromised health. The differences were considered compatible with normal short-term neonatal health.
Small statistical differences do not necessarily mean a clinically unhealthy foal. In this study, the ICSI foals were still considered clinically healthy overall.
This distinction is important when interpreting research. A statistically significant difference in one parameter does not automatically mean that the reproductive technique caused a health problem.
What does this mean for breeders?
For breeders considering ICSI, the results are encouraging.
The two studies used different populations and evaluated different aspects of neonatal health, yet both arrived at a similar overall conclusion: ICSI was not associated with evidence of poorer early foal health.
The first study found no significant differences between AI, ET and ICSI for any of the measured neonatal parameters. The second found that ICSI foals were clinically healthy and broadly comparable to foals produced through other reproductive methods.
This means that, based on the evidence currently available, the use of ICSI itself should not be considered a reason to expect poorer early health in the resulting foal.
ICSI does not guarantee a healthy foal
It is important not to overinterpret these findings.
The studies do not show that ICSI guarantees a healthy foal, nor do they prove that every ICSI foal will have exactly the same health outcome as every naturally conceived or conventionally produced foal.
Foal health is influenced by many factors, including genetics, mare health, pregnancy management, placental function, the recipient mare, nutrition, foaling conditions, neonatal care and the environment.
In the first study, for example, the researchers found differences between farms and breeds in some neonatal parameters, highlighting the importance of environmental and genetic factors when evaluating newborn foal health.
What about long-term health and sport performance?
This is where the research still has some important unanswered questions.
Both studies focused primarily on early neonatal health and adaptation. They provide reassuring information about the period around birth, but they cannot tell us everything about what happens as an ICSI foal grows.
For sport horse breeders, questions about long-term development are particularly relevant. Does an ICSI foal develop in the same way throughout its growth? What about musculoskeletal development, long-term health, fertility or athletic performance?
These questions require larger studies and, importantly, long-term follow-up of ICSI-produced horses.
The authors of the second study specifically highlighted the need for further research into the long-term health, development and sport performance of in-vitro-produced foals, as well as the possible influence of the recipient mare.
The bottom line for horse owners
Two studies published in 2026 provide reassuring evidence: ICSI does not appear to negatively affect early foal health, neonatal adaptation or most measured placental parameters.
For breeders, this is an important piece of the puzzle. Different reproductive technologies can offer different opportunities for managing valuable genetics, but the current evidence does not suggest that choosing ICSI puts the resulting foal at a disadvantage in terms of early health.
The most accurate conclusion is therefore not that “ICSI guarantees equally healthy foals”, but that ICSI foals in these studies were broadly comparable to foals produced through other reproductive techniques, with no evidence that ICSI itself compromised their early health.
As ICSI and other advanced reproductive technologies continue to develop, continued research will help us understand not only how these foals begin life, but also how they develop, perform and thrive over the long term.
Different reproductive pathways. Healthy beginnings.
For modern sport horse breeding, the latest research provides an encouraging message: ICSI can be a valuable reproductive tool without current evidence suggesting that it compromises the early health of the foal.
Scientific Sources
Study 1: Alonso MA, Dos Santos GR, Fonte JS et al. (2026). Does the Reproductive Technique Affect Neonatal Health Parameters in Foals? Reproduction in Domestic Animals, 61(3), e70192. DOI: 10.1111/rda.70192.
Study 2: Van den Branden E, Salamone M, Papas M et al. (2026). The effects of ICSI on foal health and placental parameters. Journal of Equine Veterinary Science, 164, 105982. DOI: 10.1016/j.jevs.2026.105982.
