ANALYSIS OF THE EVOLUTION OF WITHERS HEIGHT IN CHILEAN BREED HORSES

Abstract

Withers height of the Chilean breed horse was defined in 1921 and modified twice after that date. However, the estimates described in the breed standard do not seem to reflect current withers height. The objective of this study was to analyze the evolution of withers height of this breed since its origin. The withers height of 1753 registered adult horses were analyzed, considering three time periods: A 1840-1978 (n=315, 164 males and 152 females); B 1979-2001 (n=657; 455 males and 202 females); and C 2002-2016 (n=781; 521 males and 260 females). Average and standard deviation by sex and time period were calculated, and an ANOVA was performed to determine differences between average values for sexes and time periods. Average and standard deviation for withers height for period A was 1.425±0.027 m (males 1.429±0.029; females 1.421±0.025); for period B: 1.398±0.03 m (males 1.400±0.029; females 1.392±0.03); and for period C: 1.396±0.029 m (males 1.404±0.03; females 1.381±0.028). When comparing the withers height average values in total and for males between periods, significant differences were found between A and the other two periods (p<0.05), but not between them. When comparing values for females between periods, and for males and females within a period, significant differences were also found (p<0.05). In all periods, some males and females were below the limits of their respective standards for withers height. There was a decreasing number of males above the upper limit across periods, while only one female was above the limit in period B. It is concluded that withers height average (total and by sex) of the Chilean breed horse has never coincided with the estimates proposed by the breed standard, and that it has decreased over time, mainly in females.