动物育种目标的系统评估原理及其应用

本文将系统分析方法与差额法的原理有机结合起来，形成了评估杂交繁育体系中育种目标的方法。首先对整个繁育体系进行系统模拟，并计算出系统的贴现利润；然后在考虑性状的遗传变异、经济价值和性状间遗传相关的基础上，计算出各纯系中不同性状的边际效益，即该性状变化时系统总利润的改变量，由此确定出该性状的相对育种重要性和经济加权值。利用这一原理，对蛋鸡三元杂交繁育体系进行了系统模拟和育种目标的评估，分别在3个不同纯系中估计了年产蛋量、蛋重、体重、育成率、产蛋期成活率、受精率、孵化率和产蛋期耗料量共8个性状的相对育种重要性以及经济加权值。结果表明，蛋重、育成率和产蛋量分别是不同纯系中最重要的选择性状。多数性状在不同纯系中的育种重要性有较大差别，故应建立侧重点不同的专门化品系，并对各个纯系按各自的选择指数进行选择，使这些纯系在同一个配套体系内协调发展。

PRINCIPLE AND APPLICATION OF THE SYSTEMATIC EVALUATION OF BREEDING OBJECTIVES IN ANIMALS

A systematic method of evaluating breeding objectives of animals is proposed,which incorporates the methodology of system analysis with the principle of marginal method.The first step is simulating the integrated breeding system through the profit equations for each genetic group,and calculate the basic discounted profit of the whole system.The marginal return for each trait in all lines,which is defined as the increment of total profit when the trait value increases by one unit of genetic standard variation,is calculated on the basis of genetic variation,economic value of the trait and genetic correlation with other traits.Finally,the relative breeding importance and economic weights of traits can be derived.The principle is applied to simulate a three-way integrated crossbreeding system of egg-type chickens and to evaluate the breeding objectives.Eight genetic groups with different backgrounds and breeding roles are defined.A set of Profit equations are established to feature the bioeconomic characteristics for the groups and to execute system simulation.The relative breeding importance and the relative body weight(BW),livability in growing period (VR),livability in laying period(VL) fertility (FY),hatch ability (HA) and feed consumption (FC) in laying period in 3 pure lines are evaluated individually.The results indicates that EW VR and EN, are the most important breeding traits in three lines respectively.Most traits show substantial different breeding importance in different lines.And this suggests that specialized lines with different emphasis be selected with respotivc selection index,so that these lines could be developed coordinately within the integrated system.