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Life (Basel, Switzerland)2025; 15(11); 1661; doi: 10.3390/life15111661

The Role of Genetic and Environmental Factors in White Leg Markings: Prevalence and Heritability Analysis in Pura Raza Española Horses.

Abstract: White leg markings in horses are phenotypic traits influenced by genetic and environmental factors. This study analyzed their prevalence, symmetry, and genetic parameters in 38,825 Pura Raza Española (PRE) horses registered in the official studbook. White markings were scored using a binary (affected/unaffected) and a four-level ordinal scale. Most horses (38,341 out of 38,825; 98.8%) had at least one limb without white markings. The prevalence of white markings was higher in the hindlegs (17.9% LH; 14.5% RH) than in the forelegs (5.3% LF; 4.6% RF). Markings were most frequent above the fetlock (≈64%), chestnut horses showed the highest prevalence, whereas black coats showed the lowest. Genetic analyses using Bayesian animal models revealed moderate-to-high heritabilities, ranging from 0.488 for Right hindlegs to 0.574 for Left hindlegs in the multinomial model, which outperformed the dichotomous model (h = 0.030-0.515 for all legs and left foreleg, respectively). Additive genetic variance was highest in the left hindleg (σ = 7.904). Genetic correlations were high between contralateral homologous limbs (0.991 forelegs; 0.995 hindlegs), confirming strong bilateral genetic control, while diagonal correlations were lower (≈0.886). These findings confirm a substantial genetic component underlying white leg markings in PRE horses and highlight the importance of refined phenotyping and genetic evaluations for breeding strategies, particularly when markings are penalized as in the PRE breeding program.
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Publication Date: 2025-10-23 PubMed ID: 41302086PubMed Central: PMC12653778DOI: 10.3390/life15111661Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigates the occurrence and genetic basis of white leg markings in Pura Raza Española (PRE) horses, analyzing how both genetic and environmental factors contribute to these markings.
  • The research includes a large population sample to estimate heritability and genetic relationships of white leg markings, aiding in breeding decisions particularly when such markings are considered undesirable.

Research Purpose and Context

  • The study focuses on white leg markings, which are visible color patterns on horse limbs affecting their appearance.
  • White markings are known to be influenced by both genetics and environmental conditions.
  • Understanding the prevalence and genetic control of these markings can help breeders make informed decisions to manage these traits.
  • The Pura Raza Española (PRE) horse breed was chosen because it is well-documented and often subject to breeding programs where white leg markings may be penalized.

Study Population and Phenotyping

  • Data were collected from 38,825 PRE horses registered in the official studbook, providing a large and reliable dataset.
  • White markings on the legs were scored using two approaches:
    • A binary classification (affected/unaffected) indicating presence or absence of markings.
    • A four-level ordinal scale assessing the extent or size of the marking.
  • Most horses (98.8%) had at least one limb without white markings, indicating markings are not universally present.

Prevalence and Distribution of White Leg Markings

  • Higher prevalence of white markings was found in the hind legs compared to the forelegs:
    • Left hindleg (LH): 17.9%
    • Right hindleg (RH): 14.5%
    • Left foreleg (LF): 5.3%
    • Right foreleg (RF): 4.6%
  • Approximately 64% of markings appeared above the fetlock joint, indicating a common location pattern.
  • Variation in prevalence also depended on coat color:
    • Chestnut horses showed the highest frequency of white leg markings.
    • Black horses showed the lowest frequency of such markings.

Genetic Analysis Approach

  • Researchers used Bayesian animal models to estimate genetic parameters, which allow incorporating relatedness among animals and controlling for fixed effects.
  • Two modeling approaches were compared:
    • A multinomial model considering the four-level severity scale.
    • A dichotomous model based on the binary classification.
  • The multinomial model had better performance in capturing genetic effects.

Heritability and Genetic Findings

  • Heritability estimates indicate the proportion of trait variation due to genetics:
    • Moderate-to-high heritability was found for white markings using the multinomial model, ranging approximately from 0.488 (Right hindleg) to 0.574 (Left hindleg).
    • The dichotomous model’s heritability estimates were generally lower (h = 0.030 to 0.515), showing less precision.
  • Additive genetic variance, reflecting genetic diversity affecting the trait, was highest in the left hindleg (σ = 7.904), implying greater genetic influence there.
  • High genetic correlations were observed between contralateral limbs:
    • Forelegs correlation: 0.991
    • Hindlegs correlation: 0.995
  • Lower genetic correlations (~0.886) were noted for diagonal limb pairs, suggesting some shared but reduced genetic control across different limbs.

Implications of the Findings

  • The clear genetic basis for white leg markings supports their consideration in breeding programs, especially in PRE horses where such markings might be penalized.
  • Refined phenotyping using graded scales improves the accuracy of genetic evaluation compared to simple presence/absence scoring.
  • Understanding strong bilateral genetic control suggests symmetrical expression is genetically regulated and can be tracked across limbs.
  • Breeders can use these insights to select horses with desired marking patterns or reduce undesirable ones, aiding in maintaining breed standards.

Summary

  • This comprehensive study provides valuable epidemiological and genetic information on white leg markings in PRE horses.
  • The moderate to high heritability and strong bilateral correlations emphasize the importance of genetics over environmental effects.
  • Such data can significantly contribute to improving breeding strategies and phenotypic management within the PRE horse population.

Cite This Article

APA
Encina A, Sánchez-Guerrero MJ, Ligero M, Rodríguez-Sainz de Los Terreros A, Valera M. (2025). The Role of Genetic and Environmental Factors in White Leg Markings: Prevalence and Heritability Analysis in Pura Raza Española Horses. Life (Basel), 15(11), 1661. https://doi.org/10.3390/life15111661

Publication

Life (Basel, Switzerland)
ISSN: 2075-1729
NlmUniqueID: 101580444
Country: Switzerland
Language: English
Volume: 15
Issue: 11
PII: 1661

Researcher Affiliations

Encina, Ana
  • Departamento de Agronomía, Escuela Técnica Superior de Ingeniaría Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain.
  • Real Asociación Nacional de Criadores de Caballos Españoles (ANCCE), 41014 Sevilla, Spain.
Sánchez-Guerrero, María José
  • Departamento de Agronomía, Escuela Técnica Superior de Ingeniaría Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain.
Ligero, Manuel
  • Departamento de Agronomía, Escuela Técnica Superior de Ingeniaría Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain.
Rodríguez-Sainz de Los Terreros, Arantxa
  • Real Asociación Nacional de Criadores de Caballos Españoles (ANCCE), 41014 Sevilla, Spain.
Valera, Mercedes
  • Departamento de Agronomía, Escuela Técnica Superior de Ingeniaría Agronómica (ETSIA), Universidad de Sevilla, 41013 Sevilla, Spain.

Grant Funding

  • PRJ202304988 / This research has been partially financed by the VI PPIT-US. Resolución definitiva de la Convocatoria 2020 de Contratos de Acceso al Sistema Español de Ciencia, Tecnología e Innovación para el Desarrollo del Programa Propio de I + D + i de la US. (II

Conflict of Interest Statement

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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