Vashchenko P. Prediction of pig breeding values on the basis of linear models, selection indexes and DNA markers

The aim of this dissertation is the development of prediction methods for detection of pig breeding values on the basis of selection indexes and linear models with the use of DNA markers. This work demonstrates the effectiveness of the use of the linear models, DNA markers and various constructions of indexes for the prediction of pig breeding values in order to improve the existing and creating new structural elements of the breeds. It has been established that there are differences between the main production and breeding traits in the pigs of interbred types of Ukrainian Large White 1 (ULW-1), ULW-2 and ULW-3 pigs. The pigs of ULW-3 breed had higher coefficients of variation (p ≤ 0.001). This finding was used during the selection process for “Bagachanskiy” breeding type. It has also been established that the ULW-1 and ULW-3 pigs have different evaluation quality indexes (p ≤ 0.05-0.001) which suggests a sufficient specialization of ULW-1 interbred type and its sufficient predisposition for obtaining of interbreed heterosis. It is established that the developed breeding index allows obtaining a complex index for evaluating pigs by the most important productive traits which do not correlate with each other. In “Bagachanskiy” breeding herd it has been established that the developed selection index has close associations with the weight of the litter after weaning off (r = 0.72±0.030, at p ≤ 0.001) as well as with the age of achieving the live weight of 100 kg (r = -0.68±0.033, at p ≤ 0.001). At the same type two characteristics were not interrelated (r = 0.03±0.061). The linear models for evaluation of pig breeding values should be using the factors which significantly influence the production traits. The breeding traits can be influenced by the “survey order number” (p ≤ 0.05-0.01), “season of survey” (p ≤ 0.05-0.01), “the origin” (p ≤ 0.01) and “gender” (p ≤ 0.01). The models developed for determining breeding value of pigs using breeding quality characteristics, give an opportunity to identify to most valuable animals for herd replacements at early stages of ontogenesis. In the Ukrainian Large White pig breed of “Bagachanskiy” breeding type there was a significant correlation between the indicators of breeding values of sows and their female off-springs when evaluated using the newly developed models (p varying 0.05-0.001). These correlations were 9.9-10.5 times stronger when compared with the strength of the relationship between the productivity of sows and productivity of their female off-springs. Evaluation of the “Bagachanskiy” breeding boars using the BLUP method allowed the most accurate prediction and characterization of productivity traits of their off-springs. A significant relationship has been established between the results obtained by the new BLUP method and the traditional “controlled feeding of the off-springs” method when evaluating the following parameter of the pig fertilizers: the body length (0.42±0.209, p ≤ 0.05) and the backfat thickness (r = 0.67±0.170, p ≤ 0.001). At the same time, the relationship between the productivity of the boars and the productivity of their off-springs was not significantly different and was 1.4-3.5 times lower. A high degree of correlation was observed between the results of evaluation of the “Bagachanskiy” breeding pig type obtained by the linear model with the use of DNA markers (CTSL) and results obtained without the use of DNA markers r = 0.96±0.001, p ≤ 0.001). This can be explained by a low level of CTSL polymorphism in the population. MC4R DNA genotyping of Myrgorod pig breed is a useful approach for determining of the quality of fixed factors during determination of breeding values by BLUP method for the characteristics “age of achieving of 100 kg body weight” and “backfat thickness”. There were the following correlations between the results obtained using the models with and without the genotype data for MC4R gene: age of achieving of 100 kg body weight was 0.76±0.109 (p ≤ 0.001), the backfat thickness was 0.71±0.119 (p ≤ 0,001). During the selection towards a lower backfat thickness, it is important to control the equal distribution of the fat deposition because it has been established that the decrease in the backfat thickness is accompanied by deterioration of its relevant equal distribution. Pigs with a lower backfat thickness (Large White breed on Hungarian selection) are characterized by a lower coefficient of the fat equal distribution, which is by 86.9 % worst when compared to ULW-1 animals. The pigs of “Bagachanskiy” breeding type have an intermediate position. Determination of genetic trends of breeding traits obtained using the developed models demonstrated that there was a strong trend towards improving the main meat, productivity and breeding traits of the “Bagachanskiy” breeding type during the nine years of the work on creation of this pig type.