Pedigree-Based Assessment of Inbreeding Effects on Conformation and Performance Traits in the Peruvian Paso Horse: Implications for Sustainable Genetic Improvement
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https://orcid.org/0000-0003-0015-6323
Abstract
The Peruvian Paso Horse (PPH) is a breed distinguished by its unique four-beat lateral gait. Nowadays, it faces significant genetic challenges related to declining genetic diversity and inbreeding depression, which may substantially affect conformation and performance traits. This study aimed to analyze inbreeding depression in PPH, focusing on its effects on gluteal temperature and morphometric and functional traits. A total of 35 traits were evaluated in 148 animals using pedigree records from 1945 to 2023 provided by the National Association of Breeders and Owners of PPH. Bayesian animal models were employed to estimate heritability and estimated breeding values (EBVs), accounting for fixed effects, including sex, breeder, gait velocity, and age. The findings provide suggestive evidence that both the inbreeding coefficient (F) and its rate of change (ΔF) could exert measurable effects on several traits, although these findings should be interpreted as exploratory. Pedigree analyses revealed that both parents were recorded for over 94% of the animals, indicating a good pedigree depth. Certain historical periods were identified as having reduced ancestral diversity, highlighting the importance of monitoring genetic diversity to prevent population bottlenecks in the future. Inbreeding was associated with reductions in key traits, such as withers height and scapulo-humeral angle. Furthermore, ΔF suggests a more immediate and pronounced effect on specific traits. Correlations between EBVs calculated with and without inclusion of inbreeding as a covariate were significant for certain traits, suggesting that inbreeding introduces estimation bias. Preliminary analyses suggest a tendency for inbreeding to be associated with variations not only in linear body measurements but also in anatomical angles, potentially reflecting the influence of pleiotropic genes affecting multiple morphological traits. Moreover, functional and physiological traits appear to be particularly sensitive to inbreeding effects, underscoring the need for strategic genetic management of this breed.
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