OU researchers lead study on genetics of Puerto Rican horses

Researchers in Oakland University’s Department of Biological Sciences collaborated with researchers from the United States, Ukraine, Sweden and Belgium on a study examining the genetic ancestry of two horse breeds, the common Puerto Rican Non-Purebred and the Puerto Rican Paso Fino, a horse noted for its smooth, sure-footed gait.   

The study’s findings, published in the January 2022 issue of Scientific Reports, confirmed a long suspected genetic link between the two breeds, showing that the Paso Fino originated from the Non-Purebred, also known as the Criollo horse.

The results were based on mitochondrial DNA analysis and genome-wide genotyping of 200 horses, combined with publicly available Paso Fino genomes from other studies. They suggest that Criollo horses are descendants of the original genetic pool, a mix of horses imported from the Iberian Peninsula and elsewhere in Europe. 

From this admixture, the desirable traits in the horses were selected by Puerto Rican locals over a span of centuries. The Paso Fino was established on the island using the local Non-Purebred genetic pool with an important gene mutation already present – the DMRT3 “Gait keeper” mutation, which is associated with the Paso Fino’s signature four-beat, lateral ambling gait.

“Our study confirms that the Paso Fino is a native breed of Puerto Rico that has been shaped by centuries of selection by the Puerto Rican people,” said Walter W. Wolfsberger, the study’s lead author and a Ph.D. student in biological and biomedical sciences at Oakland University. The study also suggests that Criollo horses from Puerto Rico may be the source of other breeds of the Americas, such as the Peruvian Paso. 

In addition to Wolfsberger, the study’s OU-affiliated co-authors include graduate students Stephanie O. Castro-Marquez and Khrystyna Shchubelka, Special Lecturer Audrey J. Majeske and Assistant Professor Taras K. Oleksyk.

Wolfsberger, Shchubelka, Majeske and Castro-Marquez (who is Puerto Rican) worked at or attended the University of Puerto Rico at Mayaguez – a collaborator on the study – prior to coming to Oakland University. Oleksyk, the major and corresponding author on the study, taught there for over a decade before his arrival at OU in 2019. They said their ties to the island made the research especially gratifying.

Commenting on the study, Oleksyk referred to the Criollo horse as “a unique mixture of Puerto Rican horses and a valuable genetic resource that must be studied to better understand the genetics of equine traits such as appearance, behavior and gait.”

The researchers also demonstrated that the Gait keeper mutation is almost as common in the Non-Purebred as it is in the Paso Fino, a surprising finding given that no selection for gait was previously reported in regard to the Non-Purebred horses. 

“This observation has led us to explore a possible scenario in which the Paso Fino was not originally selected for the paso gait, but is a distinct horse breed that has been selected from local Non-Purebred horses in which the Gait keeper mutation was already established either by the founder effect or selective breeding by the local farmers,” said Castro-Marquez.

Along with the University of Puerto Rico at Mayaguez, Oakland University was joined in the study by Uzhhorod National University in Ukraine, Swedish University of Agricultural Sciences and Katholieke Universiteit Leuven in Belgium.

In response to the study, a bill has been introduced in Puerto Rico's House of Representatives to declare the Paso Fino a national and cultural treasure.