Authors summarized the different breeding methods used in the pig breeding sector during the last few decades. Advantages and disadvantages of the conventional selection index procedures were summarized. The superiority of BLUP breeding values over the simple phenotypic measurements are clarified. The economic aspects of the different traits are also examined and the currently most up to date economic BLUP indices were also introduced.
Genetic parameters, breeding values, and aggregate breeding values of number of piglets born alive (NBA), number of weaned piglets (NWE), and litter weight at weaning (LWWE) were predicted in the Hungarian Large White, Hungarian Landrace breeds, and in their cross (F1). Seven repeatability animal models were used. BLUP and REML methodology were used to estimate breeding values and variance–covariance components. PEST and VCE 6 software were used for estimating breeding values and variance components. Heritability for NBA and NWE was the same for all seven models. On the contrary, heritability estimates for LWWE were higher in comparison with NBA and NWE. The permanent environmental variance component was small for all traits. The large White breed had positive and significant genetic trends for all seven models and for all three traits. Landrace breed had significant trends for NBA, which was negative, and for NWE, the results were positive. The constructed indices result in one number (i.e., aggregate genetic merit); thus, the animals can be selected based on their overall performance considering the various aspects.
The application efficiency of several statistical methods was tested based on an open field behavior test of mice. The examined trait was the duration time until the animals approached the experimenter’s hand. The available time was fixed in 300 seconds. There were monitored 80 mice belonging to two different species of the Mus genus in equal proportion. Besides, male and female and young and adult animals have also represented the evaluated groups in equal proportions. The data of the examined trait was analyzed with Generalized Linear Models, Kaplan-Meier survival curves, and with Cox Proportional hazard model. The applied statistical procedure provided completely discordant results. According to the GLM results none of the examined factors (species, sex, and age) had significant effects on the examined variable. On the contrary, all factors proved to be significant using a procedure based on the survival analysis. Kaplan-Meier survival curves indicated a higher proportion of individuals successfully approaching the experimenter’s hand in all of the compared groups representing different species sexes and ages, respectively. The estimated Cox regression coefficients were significant indicating the significant effects of the species, sex, and age on the investigated trait. Based on the estimated Hazard ratios the probability that in the next time unit a successful approach of the experimenter’s hand would occur is three times more likely for one species than the other, twice as much for males and the juveniles than for the females and for the adults. Based on the present study it could be concluded that the successful approach of the experimenter’s hand by the mice is clearly “time to event data” thus it is suitable to be analyzed with survival analysis procedures. It could be concluded that applying conventional GLM was not adequate because due to the lack of the successful approach and approach times the censored data should not be used and thus the sample size would largely be reduced.
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