The use of novel phenotyping methods for validation of equine conformation scoring results

Abstract

In this experiment, which is based on a cohort of 44 Lipizzan mares from the Austrian state stud farm of Piber, we present new statistical techniques for the analysis of shape and equine conformation using image data. In addition, we examined which strategies and procedures of image processing techniques led to a successful interpretation of the traits implemented in horse breeding programs. A total of 246 two-dimensional anatomical and somatometric landmarks were digitized from standardized photographs, and the variation of shape has been analyzed by the use of generalized orthogonal least-squares Procrustes (generalized Procrustes analysis (GPA)) procedures. The resulting shape variables have been regressed on the results from linear type trait classifications. In addition, the rating scores of six conformation classifiers were tested for agreement, yielding an interrater correlation (inter-class correlation) ranging from 0.41 to 0.68, respectively, a κ coefficient ranging from 0.16 to 0.53. From the 12 linear type traits assessed on a valuating scale, only the type-related traits (type, breed-type and harmony) revealed significant (P < 0.05) results in the regression analysis of shape variables on linear type traits. The other nine traits were characterized by a lower agreement between classifiers and did not result in a significant 'shape regression'. Finally, the 'horse shape space' defined by shape variables resulting from GPA procedures offered the possibility to assist in trait definition and in the evaluation of ratings, and it is an adequate biological and objective scale to human perception of conformation, which is expressed in numerical data only.

Genome‐wide association studies based on sequence‐derived genotypes reveal new QTL associated with conformation and performance traits in the Franches–Montagnes horse breed

“…; Druml et al . ). Furthermore, the number of horses ( n = 1077) is still quite limited to typical GWAS for complex traits in humans or even cattle.…”

Association of body shape with amount of Arabian genetic contribution in the Lipizzan horse

“…Previous analyses of shape variation and conformation judging preferences in the Lipizzan population of Piber (Druml et al, 2015(Druml et al, , 2016 demonstrated that the classical Iberian or baroque Lipizzan type represents the ideal breeding goal. The advantage of this image-based morphometric approach over conventional linear measuring methods is that the retrieved model horses can be easily understood and can be used for the adjustment of conformation scoring protocols and/or breeding goals in the context of breeding programs.…”

“…For the same set of animals, which represents the actual state-owned Austrian Lipizzan breeding population, we collected standardized digital photographs following the protocol of Druml et al (2015Druml et al ( , 2016) (see Fig. S1 in the Supplement).…”

“…Finally, the configurations are optimally rotated to minimise the squared differ- ences between corresponding landmarks, which is also called Procrustes distance d (Rohlf and Slice, 1990). The process is iterated to compute the mean shape (for further information see Druml et al, 2015Druml et al, , 2016.…”

The stability of conformation and movement traits evaluation tested in cold-blooded horses of different endangerment status

“…The optimum assessment of young horses seems particularly important because improvements in the breeding efficiency of cold-blooded horses are seen in shortening the generation interval (Mantovani et al 2013), especially as the expression of some traits in cold-blooded horses changes with age, which means that it is more heritable in young horses (Mantovani et al 2010;Suontama et al 2011). The type is a trait characterized by greater scoring conventionality both in our study and in other studies (Druml et al 2015). The scores and correlations obtained are largely dependent on within-breed variation in the studied traits (Komosa et al 2013), which was rather limited in the present study.…”