Chimera Horse or Chimerism in Horses

The concept of chimeras can be traced back to ancient times. In Greek mythology, the Minotaur had a man’s body and bullhead, and Pan was half man, half goat. Similarly, certain Egyptian gods, including Sobek, Anubis, and Horus, had a human body and a beast’s head. Since Antiquity, the idea of ”chimera” has gone through a semantic change.

“Chimera” was initially a proper noun designating a fabulous creature. In contrast, “chimera” describes a living organism in modern medicine that includes various genotypes’ cells or tissues.

Nevertheless, depending on the area, there are changes to the actual sense of this term. “Chimera” in embryology refers to a mixture of cells from multiple people. Chimera” describes the combination of two DNA molecules from different individuals or different chromosomes of the same individual in molecular genetics.”

What is a Chimera Horse

A chimera is a horse formed from two genetically-different DNA forms, which occurs when non-identical twin embryos merge into one at an early stage of development.

 When the embryo grows naturally, body parts, tissues, etc., are made up of various DNA, resulting in a ”genetic mosaic” organism whose body comprises a combination of cells of two different genotypes.

 In cats and even humans, chimerism was also known

Characteristics of Chimera Horse

Sometimes, chimeras have differentiated twigs in the coat. This striking coat pattern is more typical; for example, the twin embryos were bay and chestnut.

Whereas sometimes, as this phenomenon can be found in dogs and cattle, this distinctive coat is hereditary. The DNA test for male and dandruff samples can reveal two people, and the blood test will tell whether the specimen is a chimera. Chimeras may also show a distinctive bi-colored coat.

A study conducted at a Spanish university has cast a spotlight on the rarity among chimerism horses. An individual carries two distinct genetic make-ups.

The research, carried out at the universities of Seville and Cordova, focused on the recent breeding of purebred Spanish horses, the Pura Raza Español (PRE) breed.

The study team found that sexual chimerism in PREs is not linked to infertility, despite the unusual genetic configuration.

It is known that chromosomal anomalies are one of the principal genetic causes of infertility in horses.

However, a significant proportion of these cases still go undiagnosed, probably because the signs are non-specific and diagnosis is complicated.

According to the study team, this is the case with chimeric, strongly linked with twin births in domestic animals. Its prevalence and reproductive effects are still unknown in horses.

Chimera is a genetic disorder in which two zygotes (fertilized eggs) combine after fertilization to form one single zygote that usually develops.

Chimerism in Horse

Effect of Chimerism in horses

It is an important chromosomal syndrome in animals but not investigated in horses. Last time in 1972  a research on horses done by boaters who demonstrated results that 44% of twins are born in this condition.

Chimerism is considered a pathological or abortion issue in horses, however not observed in large horses.

National Purebred Spanish Horse Breeders made research on Spanish breeds to detect abnormal chromosomes in foals.

In the biological study, chimaerism first observed in human beings later in cattle and other animals. In genetics ‘’an organism with two distinct types of chromosomes is called a chimera’’.Chimerism is common in cattle where vascular communication between the placenta disturbed and produces freemartin calf.

Freemartin condition is very rare in horses. A few horse species reported to be freemartin or under chimeric conditions.


In genetics, a horse created from two different DNA types is called a chimera horse. It is basically a condition when two embryos fuse to form a new horse. These twins appear in different brindle patterns. Different studies evaluated on french and American pony breed for confirmation of this unique behavior.


Hi, I am Waqar and active in the horse world since 2012. I have MSc (Hons) in Agriculture from the University of Agriculture Faisalabad. I love to solve equine health care issues and note down in the form of research papers. I have written hundreds of equine health care, accessories, names, and history-related blogs. My equine related work is watering a lot of horse-related magazines and blogs.

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