EVALUATION OF STALLIONS OF SPORT BREEDS BASED ON LINEAR DESCRIPTION OF THEIR OFFSPRING
During the last decade, there have been significant changes in horses' requirements, approaches and methods of evaluation in the world. The increase in the popularity of equestrian sport has led to an increase in the number of horses and the use of valuable pedigree stallions.
The level of sporting ability of horses can be determined only after the age of 10–12, therefore, the issue of early prediction and study of the laws regarding the heredity of the sportive potential is relevant for each breeding organization.
One of the first sources of data to calculate the breeding value of stallions is the linear description of the comformation and sport ability of offspring, as well as the traditional scoring system. After that, consists of a linear profile stallion for each linear trait, the complex of traits and indicates the reliability of evaluation.
Methodical approaches to estimating a comformation, sport ability and breeding values remained the same in horse breeding of Ukraine. This could not affect and quality of livestock of horses.
Horses of ukrainian riding breed is significantly inferior in performance to horses of other "modern" sports breeds, which led to a significant reduction in livestock. Therefore, it is necessary to change the system of evaluation of horses in terms of exterior and working qualities. The modern system of classification of features, in contrast to the existing rating scale, gives an idea of the nature of the manifestation of a feature by measurement, and not its desirability.
The aim of our research. Develop and scientifically substantiate the method of evaluation of breeding stallions by calculating their linear profile on the basis of the evaluation of offspring.
Material and methods. The research materials were forms containing a description of 80 horses on a linear scale. At the same time the linear profile of the stallion was formed on the basis of the generalization of the forms of at least 5 of his offspring. Thus, the results of describing the descendants of 7 stallions were processed and their generalized linear profile was formed. To describe horses on a linear scale, we developed a form that included 19 comformation traits, 9 movement traits and 9 jumping traits.
The results of evaluating the breeding value of horses for linear characteristics, that is, the genotype of individual horses were compared with the average data for the entire population. Calculation of estimates was carried out on the basis of all available from the horse, his parents, descendants and all existing relatives, data for several generations, taking into account the degree of kinship between them, the influence of factors contributing to the development of characters. This made it possible to eliminate sex and age differences, environmental conditions, as well as differences in the genetic quality of queens covered by different manufacturers (that is, the effect of the maternal genotype).
The genetic correlation coefficients were calculated on the basis of horse breeding values by the method of correlation analysis. To obtain estimates of the heritability of traits, a limited maximum likelihood method was used based on the "animal model"(DFREML 3.0 β).
Using multivariate analysis of variance, we studied the influence of such factors as gender, father, year and place of assessment, age of descendants, breed. Calculations of breeding values are carried out using a multidimensional linear model using the GLM method (general linear model). The model included a genetic and environmental correlation matrix of breeding traits. Estimates are based on solving a mixed model equation. The value of the estimates was corrected for the genetic basis, for which the average breeding value of horses was adopted, had data from 2005 to 2015.
Results of research. According to the results of research, we have developed a linear scale for evaluating horses for sports use. When compiling the list of assessment indicators, international requirements were taken into account, namely: signs are linear in the biological sense, separated from each other, have a large coefficient of heritability, each linear characteristic describes a unique part of a horse that does not cover a combination of various other signs. The scale, we have proposed, is composed according to the principle of assigning to each sign a special value from “A” to “I” depending on the deviation from the mean or desirability of the sign. For the calculation, it was assumed that the average population value for linear signs of the exterior, movements and jumps is equal to 100 units. The standard deviation is 4 units. In general, for all linear characters, low and medium heritability indicators were established in the complex (0.09–0.41). The results of the linear description of the signs of all sports horse breeds are used to calculate the breeding values of horses.
Most of the signs of offspring of stallions of Western European breeds are characterized by a good development of comformation, movements and jumps. In the offspring is to improve the balance and strength of the gallop, the trot is more elastic, the work is longer. This indicates the positive impact of these stallions on the population of horses of Ukrainian riding breed. The indicator of reliability of assessments (R) is on average 30 percent, which is insufficient for predicting the development of traits in working with Ukrainian horse breed.
The breeding value of horses of different directions of use was also calculated for the height at the withers and expressed in absolute units. So, the rate of horses is +1.08. This indicates that, on average, the height at the withers of most of the descendants of stallions will be higher than the average population level by 1.08.
Conclusions. The proposed linear method of describing the exterior, movements, jumps and character allows for a more focused selection of horses for specialization by types of equestrian sport - jumping and dressage, which in turn will contribute to improving the competitiveness of Ukrainian riding horses at the national and international levels. An important measure to improve the efficiency of breeding and breeding work should be the formation of a linear profile of stallions based on the descriptions of their offspring. Thus, breeders have the opportunity to conduct a targeted selection to increase those or other traits.
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