Genomic Diversity of the Retinta Breed Derived from Two Ancestral Bovine Lineages.

The Retinta breed, an autochthonous type of Spanish beef cattle, is highly adapted to breeding in its natural environment, which is characterized by a Mediterranean climate. The origins of this breed can be traced to two ancestral bovine stocks, which gave rise to distinct morphotypes differentiated primarily by coat color, alongside other significant traits such as growth, morphological conformation and temperament. Specifically, one morphotype comprises blond animals (Rubia Andaluza), genetically resembling the ancestral Bos taurus Aquitanicus, while the other encompasses brown- and red-colored animals (Retinta Extremeña) originating from Bos taurus Turdenatus stock. Over decades, these populations have undergone hybridization, leading to a unified population, albeit with the original subpopulations largely maintaining their genetic integrity. The objective of this study was to undertake genealogical and genomic characterization of these genetic lines, including a particular subpopulation within the blond animals (Tamarona cow). To achieve this, the genealogical records of 22,004 active animals were analyzed, and over 63,000 SNPs from a total of 1030 animals were examined for genomic characterization. Genealogical analysis revealed pedigree completeness and a high level of effective population size (Ne) across the entire population, yet relatively low Ne values within each pure line (ranging from 28.38 to 34.47). These findings underscore the ongoing efforts of the National Association of Retinta Breeders (ACRE) over the past decades to mitigate the loss of variability in this breed. The genomic characterization highlights the persistent differences within the original population and the predominant influence of the Retinto line within the current breed, as evidenced by principal component analysis (PCA) and admixture analysis. Furthermore, the identification of the Tamarona subpopulation within the blond lineage underlines its unique genetic composition, warranting its recognition as an official genetic line within the current Retinta breed. Given the small population size of these lines, particularly the Tamarona subpopulation, protective measures are imperative to preserve this distinct gene pool. Such measures would enhance the genetic diversity of the Retinta breed, which is essential for sustainable breeding practices in its natural habitats.