ABSTRACT - The objective of this study was to determine the effects of morphometric measurements on race performance (m/sec) of Thoroughbre...
ABSTRACT - The objective of this study was to determine the effects of morphometric measurements on race performance (m/sec) of Thoroughbred horses. Data of morphometric measurements (withers height, rump height, chest girth, chest width, front chest width, chest depth, neck length, shoulder length, length of withers to rump, rump length, body length, head width, head length, and cannon circumference) were taken from 244 Thoroughbred horses chosen at random. A total of 2888 racing records were considered for race performance. The effects of environmental factors on morphometric measurements (stallion, gender, age, and mother age) and race performance (gender, age, mother age, year, hippodrome, race distance, racetrack, and race type) were analyzed using the least squares method. Principal component analysis (PCA) was performed for morphometric measurements, and then the factor loadings were rotated by Varimax method. Multiple linear regression analysis was applied for the significance of the obtained factors on race performance.
Significant effects for stallion on all morphometric measurements, except head length and width, and for gender on withers height, cannon circumference, and head width were determined. Race performance was significantly influenced by stallion, gender, age, year, hippodrome, race distance, racetrack, and race type. After PCA, four factors with eigenvalues >1 were attained. The effects of factors on race performance were not significant, according to the results of multiple linear regression analysis. Therefore, the effects of the morphometric measurements examined on the race performance were not significant in Thoroughbred horses. Keywords: environmental factors, morphometric measurements, PCA, flat racing Yavuzkan Paksoy1, Necmettin Ünal2* 1 Yeşiloba Hippodrome, Adana, Turkey. 2 Ankara University, Faculty of Veterinary Medicine, Department of Animal Breeding and Husbandry, Ankara, Turkey.
*Corresponding author: unaln@ankara.edu.tr Received: March 6, 2018 Accepted: April 10, 2019 How to cite: Paksoy, Y. and Ünal, N. 2019. Multivariate analysis of morphometry effect on race performance in Thoroughbred horses. Revista Brasileira de Zootecnia 48:e20180030. https://doi.org/10.1590/rbz4820180030 Copyright: This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction It is widely accepted that the horse was domesticated in the years 3000 BC, after dogs, sheep, goats, and cattle. After domestication, horses started to be used for various purposes, which have changed throughout history. Nowadays, horse breeding is mostly undertaken for sport and recreation purposes (Taylor and Field, 2014). Horses have been also used for transportation and farming in some countries (McManus et al., 2013; Tennah et al., 2014).
The Thoroughbred horse breed is mainly known for running, especially flat racing, but is also used in a variety of sports such as jumping, hunting, three-day eventing, dressage, and polo. Flat racing with Thoroughbred horses has a very important place in equestrian sports around the world. This breed has been improved for speed at middle - distances (1400-2400 m) (Evans et al., 1994; Taylor and Field, 2014). R. Bras. Zootec., 48:e20180030, 2019 Multivariate analysis of morphometry effect on race performance in Thoroughbred horses Paksoy and Ünal 2 Horse performance during the race is measured in various forms. In flat racing, speed (m/sec) is a measure largely used in assessing race performance. Many factors influencing race performance of Thoroughbred horses (e.g., husbandry, nutrition, exercise, race distance, racetrack, gender, handicap weight, age, mother age, and hippodrome) have been addressed in some studies (Oki et al., 1994; Barron, 1995; Ekiz and Kocak, 2007; Buxadera and Mota, 2008; Bakhtiari and Heshmat, 2009; Paksoy and Ünal, 2010; Park et al., 2011; Takahashi, 2015). Morphometric measurements of horses are considered a criterion in determining breed characteristics and body conformation. In addition, they are important in monitoring development during the growth period and in determining the suitability for breed standards in the post-growth period. Thoroughbred horses are required to conform to the breed characteristics in various body measurements. Many studies involving morphometric measurements in different horse breeds have been carried out (Anderson and McIlwraith, 2004; Staniar et al., 2004; Gücüyener Hacan and Akçapınar, 2011; Yılmaz and Ertuğrul, 2012; Padilha et al., 2017).
On the other hand, no research has been found on the impact of morphometric measurements of Thoroughbred horses on their race performance (m/sec). Only one study (Smith et al., 2006) reported that withers height, rump height, body length, and heart girth of yearling Thoroughbred foals were positively correlated with lifetime earnings and win percentage. Principal component analysis (PCA) is the simplest of the true eigenvector-based multivariate analyses. It is most commonly used to intensify the information included in a large number of variables, strongly correlated, into a smaller set of new composite dimensions, without much loss of information. It does so by composing new uncorrelated factors that successively maximize variance (Sadek et al., 2006; Park et al., 2011; Alpar, 2013). The purpose of this study was to evaluate the impact of morphometric measurements on race performance of Thoroughbred horses using multivariate analysis.
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