Abstract
Abstract: The objective of this work was to evaluate the development of the morphometric characteristics of Mangalarga Marchador horses through nonlinear models. The transversal method was used to collect data on height at the withers (HW), body length (BL), and thoracic (TP) and cannon (CP) perimeters from 200 horses (75 males and 125 non-pregnant females), aged between 6 and 153 months. The parameters of the Brody, Gompertz, logistic, and von Bertalanffy nonlinear models were estimated using the R software. Models were compared and selected using the coefficient of determination, the residual standard deviation, and the corrected Akaike information criterion. For adult females, HW, BL, TP, and CP ranged between 146.45-148.34, 148.59-151.64, 179.07-182.88, and 18.25-18.76 cm, respectively. For males, HW, BL, and CP ranged between 148.55-151.80, 150.77-154.88, and 18.95-19.41 cm, respectively. The logistic model best expresses growth in HW for males and females, as well as in BL and CP for males, whereas the Brody model is the best predictor for HW, BL, TP, and CP for females. The increase in the values of the morphometric measurements is more rapid and homogeneous between the ages of 6 and 24 months, stabilizing at 60 months in both sexes.
Highlights
The Mangalarga Marchador horse breed, originated from southern Minas Gerais, Brazil, has been rising in popularity in recent years due to its characteristics, including comfort and docility, which are attractive for leisure and equestrian competitions (Fonseca et al, 2017)
The morphometric variables determined were: height at the withers, measured from the highest point of the interscapular region, located in the space defined by the T5 and T6 spinal processes, to the ground; body length, distance between the cranial portion of the major humerus tubercle and the caudal portion of the ischial tuberosity; thoracic perimeter, circumference measured just after the end of the withers, between the T8 and T9 spinal processes, passing through the intercostal space of the eighth and ninth vertebrae until the joint between the last rib and the xiphoid process; and cannon perimeter, circumference measured in the median region of the left shin, formed by the metacarpal bones II, III, and IV
These differences in the fit quality of the models may be related to the breed biotypes: all horses are saddled, the Mangalarga Marchador breed was developed for work, while the other ones were developed for sport. Another explanation for these differences is the use of the transversal method for data collection in the present study, since the quality of the obtained fit may be related to the independence of errors due to nonrepeated measurements in the same animal (Carneiro et al, 2014); this shows the efficiency of the method and that it can be used to describe the growth of the Mangalarga Marchador breed
Summary
The Mangalarga Marchador horse breed, originated from southern Minas Gerais, Brazil, has been rising in popularity in recent years due to its characteristics, including comfort and docility, which are attractive for leisure and equestrian competitions (Fonseca et al, 2017). These models allow predicting animal growth and maturity, aiding in the management decision-making process, which helps to maximize animal production, considering the interpretation of the models’ parameters (Freitas, 2005; Carneiro et al, 2014; Teleken et al, 2017) In these models, animal growth is typically determined by morphometric measurements (Lawrence & Fowler, 2002; Cabral et al, 2004; Santos et al, 2007; Rezende et al, 2016), including height at the withers, body length, and thoracic and cannon perimeters. Morphometric measurements can be used to select animals capable of superior performance
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