Use of entropy in the analysis of nominal traits in sheep

In the analysis of dependencies between nominal traits entropy and its function, mutual information seems to be a proper descriptive statistic. This is shown by characterizing the relationships between the prolificacy of dams and selected genetic attributes: the genotype of transferrin, the genotype of hemoglobin, and the type of birth, as well as the environmental attribute, i.e., year of birth. The entropy method may improve the exactitude of investigations concerning the influence of different factors on production trait. The index of relative uniformity, introduced in this study, proved to be an adequate tool for the determination of similarity in the examined flocks. The application of mutual information in the determination of values of the dependence measures in the analyzed experiment was justified

Synergy factors in the analysis of lamb survival

Survival is one of the most important traits in genetic improvement programmes in livestock. The objective of this study is to determine sex, inbreeding, and birth type effects as well as their interactions on birth survival in lambs of two breeds. Records of 6356 Polish Merino (PM) breed and 9143 Wielkopolska sheep (WS) were taken into the analysis. Relationships between survival and three binary variables (sex, inbreeding, type of birth) were estimated by the use of logistic regression. Interactions among these variables were also included in the model. Thus, the odds ratios and synergy coefficients were estimated. Lowest birth mortality was registered for inbred females from single birth. Differences in survival between the studied breeds were observed. Negligible single effects of sex, inbreeding and birth type for PM were estimated, whereas for WS these effects were significant (P<0.01). Opposite dependencies were obtained for interactions among these variables. In the case of PM, synergy between birth survival and joint effects of sex-inbreeding, sex-birth type, sex-inbreeding-birth type were highly significant, but for WS only inbreeding-birth type interaction was considerable. Hence, a generalisation of the obtained results seems to be difficult: they exhibit a very complex background of lamb survival