Caracterização racial de equinos Mangalarga Marchador: como aprimorar o registro genealógico e critérios de seleção?

Abstract

The Mangalarga Marchador (MM) constitutes a genetic group formed by saddle horses with a gait type called "marcha." The objective was to summarize the morphometric characteristics that showed greater variability in a subpopulation of adult MM horses, as well as to analyze the morphofunctional profile of offspring from different ancestors of this horse breed, aiming to improve the genealogical registration system and selection criteria applied in practice. Chapter I presents a literature review on the history, importance, breed standard, genealogical registration system, and studies on morphometric evaluation of the MM horse. Chapter II presents a scientific article in which a principal component analysis (PCA) was conducted to summarize the phenotypic variability (linear and angular measurements, "triangle" and "Z" of the gait, weight, and zootechnical indices for functional aptitude evaluation) of 273 adult MM horses registered in the MM-5 and MM-6 studbooks (with known genealogy) at the Brazilian Association of Mangalarga Marchador Horse Breeders (ABCCMM). Subsequently, a comparative analysis of the PCA scores for these morphofunctional characteristics, related to approximately 70% of the total variability of the studied phenotypes, was carried out with the gait and morphology scores obtained at the time of definitive registration of these animals. The low association of the calculated scores for the morphometric variables with the subjective scores for gait and morphology scoring of horses registered in the official genealogical control service of the MM breed, combined with the fact that only seven of the 12 mandatory linear measurements in this process were related to the variability of the studied animals, suggests a review of the current genealogical control system, aiming to improve the conservation and enhancement of phenotypic characteristics of interest in this genetic group of Brazilian horses. Chapter III presents a second scientific article in which, based on the PCA results described previously, the aim was to evaluate phenotypic divergences in the morphofunctional profile of 210 adult horses descended from 18 ancestors of the MM breed. There were some phenotypic divergences among the progenies of the different sampled ancestors, suggesting the existence of families within this horse breed. Progenies that presented values of chest width (≥ 27.63 cm), rump length (≥ 44.25 cm), and knee circumference (≥ 27.50 cm) were associated with their respective ancestors included in the MM elite studbooks. Therefore, a review of which body measurements should be part of the systematic definitive registration of the MM horse can contribute to the identification of superior animals, according to the criteria provided in the current breed approved by MAPA and controlled by ABCCMM.