An investigation with 1929 sheep from the Caucasian Merino breed at different age and comprising at the period 2003-2010, belonging to the Kabiuk was carried out. Live weight at weaning, at 9 months, at 1.5, at 2.5 years of age and biological fertility at 2.5, at 3.5, at 4.5 and at 5.5 years were studied. The evaluations of the variance, representing the effects of the factors included, and the F-values of significance of each of them were established. The effect of year of birth (A), breeding line (B) and mating scheme (C) were studied. LS-estimates were resulted for each class of each source of variability, heritability coefficients of the controlled productive traits and coefficients of determination for the applied model. All the evaluations and analyses were based on multi-factor linear - statistical models (Harvey, 1990): It was established that the year of birth is a significant source of specific variability for the traits live weight (Р 0.001) and biological fertility (Р 0.01, Р 0.05) of all studied ages. The applied mating scheme has a significant influence on the trait live weight at weaning. Heredity determined variability, relevant to lineage for the live weight and biological fertility was not established. The genetic determination of live weight at 18 months is high (h2 = 0.817) and guarantee a successful selection by phenotype in Caucasian population at that age.
Effect of different sources of specific variability on live wieght and fertility traits in caucasian marino breed