using classification trees in statistical analysis of discrete sheep reproduction traits

The research material covered 2-8 year-old 6,586 Polish Merino ewes. Ewes were obtained from ten flocks located in the Pomorze and Kujawy Region (Poland). The reproductive performance index (the number of reared offspring from mated mother/year) was analyzed. The data collected were verified statistically using the classification tree technique, followed by the analysis of variance. The average number of the offspring reared by ewes was 1.208 lambs and was similar to the corresponding data presented in the applicable literature reports on Polish Merino sheep breed. To identify the factors which were responsible for the variation in the number of offspring reared by the mated ewe, the classification tree technique was applied. As a result of this statistical procedure, the ewe lambing information set was divided according to the factors which demonstrated the highest power of the ‘importance’ index: mother’s age, flock, birth type and the body weight of ewes at the age of 12 months. The effect of the factors identified with the use of classification tree technique on the offspring number per mated ewe was significant, which was seen from the analysis of variance. The results suggest that the classification tree technique can be used to provide the statistical analysis of discrete reproduction traits.