Iwona Janczarek
Objectivisation of judging methods of free jumping in young half-bred stallions
Introduction. Most frequently used method of estimation jumping abilites in young horses estimated in free jumps leads to many controversies. To date, detailed traits of a proper jump were not defined and the importance of the traits was not determined, either. Jumping qualities are estimated during performance tests by judges who award marks, which is a subjective method. With regard to the crucial role of the early estimation of the horse’s performance, objective methods of judging are searched.
Aim. The objective of the study was to improve methods of estimation free jumps exemplified in young half-bred stallions by: 1) selection of independent traits most responsible for basic jumping parameters, as well as determination the trait weights and desirable levels in view of defining the long and high jump; 2) analysis of influence of some factors on the trait level; 3) elaboration of measurable method of estimation free jumps in young stallions; 4) comparison of the own method with the method applied in Poland in performance tests and on this basis designing a method of improving the current system; 5) estimation of genetic parameters of the traits and establishing if they are correlated with stallion body measurements.
Material and methods. The material consisted of video film of 2750 free jumps of 550 stallions during 100-day performance test. 15 jumping elements were chosen (film frames) and digitally analyzed by 127 measurements of each jump (349 250 measurements, in total). The measurements were the basis to construct seven jump formulae. 27 body measurements of each stallion were taken. Of the jumping traits, basic jumping parameters were distinguished (dependent traits) which measure the jump effectiveness, and traits describing the jump length and height (independent traits). Most important independent traits were selected with the use of statistic methods in three-stage elimination based on the degree of connection with dependent traits (Pearson’s and Spearman’s correlations, multiple regression, determination, element standardized regression, percent of independent variables in the description of dependent variables). In order to find if the value of selected independent traits in a good jumper should be high or low, the significance, level and sign of correlations with dependent traits were analyzed. The selected independent traits were used in designing the stallion’s Phenotypic Quantity Jump Index (PQJI) based on the computer measurements of the filmed jump. The impact of some factors on the independent traits and PQJI was determined with the use of multifactor analysis of variance, whereas the significance of differences between means was estimated with multiple T-Tukey’s test. The connection between the independent traits and PQJI versus official marks for free jumps, as well as stallion body measurements was examined with the use of Pearson’s and Spearman’s correlations. Heritability and repeatability of the independent and dependent traits was estimated with REML procedure, multi-trait and single-trait individual models. 
Results and discussion. 15 most important independent jump traits were found. The long and high free jump of a young stallion should consist in approaching the obstacle with possibly long time of the last step before take-off, considerable distance of take-off with particular legs and increasing distance of hind legs relative to front legs from the obstacle front, most quick take-off of the front legs, keeping the neck lowly, long period of support with the hind legs, carrying the front legs in the least possible distance between hooves and sternum, as well as maximum angle of trunk hind part lifting during landing. Other favourable traits are as follows. lengthening the time of carrying hind legs over obstacle relative to the time of carrying front legs, lengthening the time of carrying front legs during preparation to landing relative to the time from front leg take-off to passing the obstacle highest point, as well as lengthening the time between carrying hind legs over the obstacle and landing with the first front leg. The independent traits and PQJI were of the most desired values in Bogusławice Training Center, in Małopolski stallions, in the oldest individuals and during jumping the highest obstacle. The correlations with official marks for free jumps in performance tests turned out to be insignificant, showing serious drawbacks in the current estimation system. To improve the current performance test, Phenotypic Qualitative-Quantitative Jump Index (PQQJI) was suggested. The value of direct measurements of independent traits are to be replaced in it by marks awarded by selectors. The selected independent traits showed slightly lower heritability and repeatability than the dependent traits, whereas correlations within the independent and dependent traits, as well as between them, were high. The independent traits and PQJI are favourably affected by not too big size of the horse, long croup in ischium part, not too long legs and not too short hind cannon.
Conclusion. The analysis of almost three thousand jumps documents which are the traits of the long and high free jump of a young half-bred stallion. Defining these properties enables specifying and making more objective systems of early estimation of horse jumping qualities. The suggested Phenotypic Qualitative-Quantitative Jump Index may be used in individual estimation of young stallions in the view of basic jump parameters. Genetic correlation between some dependent and independent jumping traits makes possible to use the latter in the selection of young half-bred stallions.