Morphometric characteristics of the Mangalarga Marchador horse breed determined by nonlinear models

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.

Growth curve for height at withers and body length of Mangalarga Marchador horses

“…The curve obtained by the plateau model showed that the age at which the growth plateaued varied between 65.4 and 67.5 months for height at withers and 67.3 and 72.1 months for body length for females and males, respectively, as evidenced by the growth curve (Figure 1 -B) and by the t 0 value (Table 1). This indicated that the plateau model overestimates age, as suggested by SOUZA et al (2019), who also reported this growth pattern in the Mangalarga Marchador breed.…”

“…An alternative is to use a cross-sectional method, where the variables can be collected once per individual. This methodology has been demonstrated to be effective in human (SPERANDIO et al, 2011) and equine (RIBEIRO et al, 2018;SOUZA et al, 2017;SOUZA et al, 2019) growth studies.…”

Growth predictability models in Mangalarga Marchador horses

“…In addition, the limited number of studies on the growth of morphological traits in horses demonstrated the difficulty of obtaining data. As confirmed by SOUZA et al (2019), MM horses, for example, grow until they are 5 years old, and the owners of the stud farm mostly sell the animals before reaching this age. Thus, to enable growth studies with a larger number of animals and to better understand the development of a given population, the use of cross-sectional data collection is recommended (SILVA et al, 2010;SPERANDIO et al, 2011), where the variables can be collected only once in each animal, as efficiently demonstrated by RIBEIRO et al (2018), SOUZA et al (2017), and SOUZA et al (2019 in horses.…”

Cross-sectional and longitudinal method for describing growth curve of rabbits

“…Commonly, studies of animal growth curves are performed using the longitudinal method, which seeks to monitor its evolution over time. However, some researchers have used the crosssectional method, which uses similar animals at different times, for example, animals of the same breed raised in the same environment (Ribeiro et al 2018;Souza et al, 2019). The von Bertalanffy model is also used for plants growth, and in some cases, the cross-sectional data methodology is used when it is not possible to use longitudinal data, especially in dry matter and drying studies (Macedo et al, 2017).…”

“…However, studies comparing methodologies using rabbit's data are still scarce. Some researchers have already used the crosssectional method as a substitute for the longitudinal method, as can be seen in the works by Ribeiro et al (2018) and Souza et al (2019) for 'Mangalarga Marchador' horses. Thus, for this type of growth curve analysis, comparing results using different methods is plausible, since the cross-sectional method may be a possible alternative for this type of study.…”