THE EFFECT OF POPULATION-STRUCTURE ON THE GENETIC GAIN OF BREEDING PLANS FOR CHINESE MERINO SHEEP

The model calculation for optimization of breeding programs for Chines e Merino sheep was carried out in order to study effect of the populat ion size on breeding profit and genetic gain under consideration of th e proportion of test mating in the active breeding material (ABM) and number of test rams. The results were as follows: The breeding profit and monetary genetic gain are increased with the population size from 20 000 to 160 000 ewes. The proportion of ewes that mated with test ra ms should be increased over 50% in the ABM (= breeding population). In a population size of 20 000 to 40 000 ewes, if 20 to 30 test rams are tested per year, the optimal genetic gain would be realized. The numb er of test rams should be increased from 50 to 70 in a large breeding unit.