Đang chuẩn bị liên kết để tải về tài liệu:
báo cáo khoa học: "Single and two-stage selection on different indices in open nucleus breeding systems"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Single and two-stage selection on different indices in open nucleus breeding systems | Génét. Sél. Evol. 1984 16 1 103-120 Single and two-stage selection on different indices in open nucleus breeding systems J.p. MUELLER School of Wool and Pastoral Sciences The University of New South Wales Kensington N.S.W. Australia 2033 Summary When different information is available from the various parts of a population the construction of correspondingly different selection indices is required. Selection criteria used for males may differ from those for females and in open nucleus systems indices for the nucleus may not apply for the base. In order to test the effects of alternative allocation of selection efforts and to find the optimum breeding design in each case formulae were adapted to predict the rate of genetic gain in open nucleus systems with varying selection criteria. Selection on different index sets may occur in one or two stages including progeny testing. Evaluations for a range of arbitrarily chosen index sets indicates that the genetic gain in a nucleus system is particularly sensitive to changes in the relative accuracy of indices used for sires and for base females. A similar improvement of selection accuracy of sires and base females increases genetic gain by 20-45 p. 100 and 10-20 p. 100 respectively. The higher limit is achieved when selection accuracy in the opposite sex is low. In two-stage programs and progeny testing schemes results depend on the relative accuracy of indices used in the two stages. When sires are most accurately evaluated opening the nucleus adds little to the gain in the system whereas accurate selection of base born females in a single stage or after a first screening makes the open nucleus structure very attractive. The results are used to compare alternatives and optimise design in a simple sheep example. Key words Population structure index selection progeny test open nucleus system. Résumé Selection en une et deux étapes sur differents indices en systèmes à noyau ouvert L existence d informations specifiques à des