Heritability estimates and genetic trends for performance test traits in the Old Kladruber horses

© Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources


Introduction
Old Kladruber horse is an important Czech genetic resource and origin of this breed dates back to 400 years ago.Horses was bred especially for ceremonial purposes and the Baroque type of the breed has been conserved until now.The population is bred in grey variety and black variety.In recent years horses are selected mostly on type of galakarossier and the primary goal of the breeding program is conservation of the gene pool with respect to conformation, gaits and sport performance, especially for carriage driving and dressage.
Organized selection programs has resulted in positive responses in several horse breeds.With increasing performance in equestrian disciplines is mostly related increasing genetic trend.Positive genetic trend has been achieved in Swedisch warmblood horses (Viklund et al., 2011), Selle Francais (Dubois and Ricard, 2007), British sport horses (Steward et al., 2010) or in Lusitano horses (Vincente et al., 2014).
No genetic analyses of performance test data of Old Kladruber horse have yet been conducted.Estimated breeding values would allow maintaining the characteristics of the breed with regard to conservation of the Old Kladruber horse.The objectives of this paper were estimation heritability coefficients, prediction breeding values and provide information about genetic trends evaluated traits in performance test.

Data set and Pedigree
Performance test of Old Kladruber stallions and mares are two days.Together eight traits are assessed: rideability, overall impression walk, trot, canter, driveability of carriage -dressage test and obstacle driving test.Rideability and gaits are assessed under saddle and driveability of carriage is assessed in harness.Each trait is scored between 1 (very poor) and 10 (excellent).
The data set was obtained from the studbook of the Old Kladruber Horse and Central Register of Horses.The data set from performance test comprised 704 individuals from the period of 1995 through 2014.Evaluations of the horses were obtained from the all of the judge, each animal had three to five evaluations per test (not just only average mark).With a repeated measurements, 2,326 observations were in the data set.Including four generations of ancestors, 1363 horses were included in the pedigree file.

Estimation of genetic parameters and breeding values
Estimates of heritability coefficients were estimated by single trait models.Variance components were analysed with Gibbs sampling algorithm using GIBBS1f90 software (Misztal, 2002).Breeding values prediction were calculated according to the following equation: The genetic trends were calculated from the means of the RBV results for individuals born in the same year.The annual genetic trend was defined as the genetic progress in genetic standard deviation units per year and computed by linear regressions of average RBV on birth year divided by 20 (genetic standard deviation).Annual genetic trend was computed for horses born 1991 to 2009.

Statistical description of traits and heritability coefficients
Means, standard deviations, ranges of point scale and coefficients of heritability are presented in Table 1.Mean scores for the traits were in the range from 6.8 to 7.8 and the standard deviations were in the range from 0.8 to 1.1.

Genetic trend of Old Kladruber horse
The genetic trends for all traits in Old Kladruber horse are presented in Figure 1, 2 and 3.All genetic trends were

Conclusions
Heritability estimates were low (0.08-0.23) for all traits in performance test.Genetic trends were constant over the analysed period, annual genetic change were close to zero in all traits except type and gender expression and trot which is undesirable phenomenon in view of conservation Old Kladruber horse on type of galakarossier.Small genetic variability for all analysed traits in performance test suggested that primarily attention must be given to maintaining genetic variability and minimizing the rate of inbreeding in the population.Selection among horses using estimated breeding values would allow maintaining the characteristics of the breed such as type and gender expression or trot which is in accordance with the breeding objective.
Variety k + YearPlace l + Stud m + + Classifier n + PE o + Animal p + e ijklmnop a ) Breeding values were standardised (Relative breeding values -RBV) on a scale with mean 100 and standard deviation of 20 points.
To the model equation were gradually included the effects of age horses, sex, year*place of performance test, variety and stud.Fixed effects explained from 31% to 46% of the total variability.Most of variability (from 15% to 22%, depending on analysed trait) explained the effect of the year*place of performance test.Other effects explained from 1.5% to 3%.Reason for inclusion fixed effects of variety and stud is in history of Old Kladruber horse breeding because both variants were raised separately from 1945 to 2005.Vincente et al. (2014) indicated in the study of the Lusitano horses, preliminary analyses of the fixed effects for morphological and functional traits accounted from 14 to 35% of the phenotypic variability.