PSVII-16 - A method to analyse the vertical acceleration of the Peruvian Paso horse for animal breeding purposes

Abstract: The Peruvian Paso Horse (CPP in Spanish) is an equine local breed in Peru. In this kind of horse, the smoothness and harmony of its movement come from the combination of the mechanisms of movement during the “paso llano” and the correct degrees of execution of the overreach with the adornments. The Peruvian Paso horse is internationally recognized for the smoothness of its gait, which is known as "the smoothest riding horse in the world". This characteristic is evaluated in breed competitions. However, at this time, there is no measure available to determine the smoothness of the gait objectively, relying solely on the judge's perception during the evaluation. The objective of this research is to analyse the vertical acceleration of each animal (a_i) during the “paso llano” gait in CPP. Sixty-five stallions and sixteen mares were measured through video recordings using a camera with a resolution of 1920 x 1080 megapixels at 30 frames/s. The animals were pulled by an operator at a “Paso llano” with an approximate speed between 2.5 and 4 m/s. The gait of the horse was recorded by filming on a tripod with a fixed position positioned horizontally at 1.3 meters height and 12 meters from the middle of the line of motion. To identify the reference point for measuring, a 4 x 4 cm tape was attached to the left side of the croup. KINOVEA software version 0.9.5 (https://www.kinovea.org/) was used to analyse the vertical acceleration every 33 ms. The digitized coordinates are passed through the Butterworth filter at a cutoff frequency computed by estimating the autocorrelation of residuals and finding the frequency yielding the residuals that are the least autocorrelated. The filtered data set corresponding to this cutoff frequency is kept as the result. A graphical representation can be seen in Figure 1. Root-mean-square (RMS) for each horse was calculated as follows: RMS = √(∑ a²_i / n), (a_i with i = 1 . . . n). To determine normality assumptions, the Anderson-Darling test with p >0.05 was applied. To determine if there is a difference between sexes, an ANOVA with p< 0.05 was applied. Levene's test was applied to determine the equality of variances. The descriptive statistics are presented in table 1. The Anderson-Darling test obtained p=0.969, therefore, the assumptions of the normal distribution are fulfilled. Levene's test obtained a p=0.035, therefore, the assumptions of equal variance between sexes are not met. ANOVA with heterogeneity correction Welch was p=0.891. The results show that there is no difference in vertical acceleration between males and females. The estimation of RMS allows an objective analysis of the smoothness of gait in the CPP and can be used as a selection criterion in selection for breeding plans.