【作者】 任建存；

【导师】 昝林森；

【作者基本信息】 西北农林科技大学 ， 动物遗传育种与繁殖， 2008， 硕士

【摘要】 本文根据育种现状和生产实际,从秦川肉牛育种的实际需要出发,通过研究分析,提出建立秦川肉牛群选群育开放核心群育种体系;利用秦川牛群体育种学、生物学和经济学等参数,采用基因流动法和ZPLAN专用程序研究了秦川牛开放核心群的的优化育种规划;在对现行育种方案预期育种效果分析的基础上,研究了不同群体结构、公母牛使用年限、核心群开放程度和不同群体规模等因素对群体综合育种进展、育种效益及世代间隔的影响;并且提出了改进现行育种规划的最优化育种技术指标体系。在研究工作中,主要得到了以下结论:1.为加快秦川牛的选育改良进度,改进封闭式核心群育种方式的不足,固定性状,培育优秀个体,采用群选群育开放核心群育种体系。秦川肉牛开放核心群育种体系共分三个层次:核心群、育种群和改良群,是一个呈等级的金字塔型结构,顶部为核心群,中部是育种群,基部是改良群。核心群由最优秀的公、母牛个体组成,育种群和改良群则由来自繁殖群、商品群中经性能测定的个体组成。2.对于大群体来说,在正常选择强度下,当核心群数占总群体的10%时可获得最大的遗传进展,在核心群占总群体的5%～10%时,核心群中的母畜应有一半来自基础群(育种群和改良群),开放核心群可获得较高的遗传进展率。3.从基础群选留母牛的最佳比例随着公牛选择强度的提高而增大,但随着母牛选择强度的提高而减小。在不限制公、母牛迁移方向的情况下,当上层群体50%的更新母牛和5%～20%的更新公牛来自下层群体,且下层群体50%的更新公牛来自上层群体时,所获得的遗传进展是最大的。4.ONBS中连续迁移的效应往往导致亚群和总体同基因频率、群体均值、群体方差更加接近,群体同质性增加。与CNBS相比,ONBS以其特有的迁移同质化效应,可以缓冲小群体复制育种中突出的源于配子抽样的群体遗传特性随机波动和抽样偏差,从而以渐进方式与总体保持遗传同质性。迁移和选择的联合遗传效应往往使得ONBS的遗传进展远大于封闭体系。5.在设定规划期为20年,牛群规模为2500头繁殖母牛的条件下,对现行育种方案进行了分析。现行育种方案在群体规模、育种群比例、种公牛利用情况和开放程度等方面尚未处于最佳状态。现行育种方案在母牛一个产犊周期可实现的综合育种进展为46.83元,育种产出量为214.75元,育种投入量为32.33元,育种效益为182.42元,平均世代间隔为5.26年,投入与产出比为1:6.64,与国内外研究相比改进余地很大。6.当公犊牛的留种比例为0.6,母犊牛的留种比例为0.8时育种方案能获得较好的育种效益和相对较高的遗传进展,同时也比较符合生产实际。7.通过分析得出不同选择组动物使用年限的最优化育种方案,核心群公牛和育种群公牛的最理想使用年限为1年,核心群母牛和育种群母牛的最理想利用年限为5至6年,测验公牛最理想使用年限为1至2年,测验母牛最理想使用年限为4至5年,改良群公牛最理想使用年限为1年,改良群母牛最理想使用年限为6年。8.对现行育种方案的育种效率和使用年限优化后的育种效率进行了对比分析,结果为:优化使用年限优化后获得的综合育种进展、育种产出和育种效益分别较现行方案提高了25%、37%和42%,世代间隔较现行方案缩短了15%。投入与产出比由1:6.64提高为1:8.23。9.在核心群比例固定的情况下,随着群体规模的扩大,核心群规模也越大,育种投入量(固定投入)将随着群体规模的扩大呈递减的趋势,而群体的综合育种进展、育种产出和育种效益都呈递增的趋势。10.本研究通过综合分析,优化全部影响因素后,在群体规模为2500头繁殖母牛时核心群、育种群和改良群比例分别处于7%～9%、11%～13%和80%,核心群母牛开放程度小于20%时,其综合育种进展和育种效益最高。研究认为,核心群验证公牛使用1年,其他公牛使用3～4年,母牛使用5年,改良群母牛的20%～40%由核心群公牛配种时可获得理想的育种效益。群体可以达到的最佳世代间隔为4.05年,综合育种进展可达到61.72元,育种产出可达到306.61元,育种效益可达到270.83元,分别比现行育种方案提高了23%、32%、43%和48%,优化后育种的投入产出比为1:8.56。更多还原

【Abstract】 According to present breeding situation, production practice and real needs in Qinchuan beef cattle breeding, the paper analyzed and established an open nucleus breeding system (ONBS) of Qinchuan beef cattle through population-based selection and breeding, researched on the optimized breeding program in the ONBS according as parameters of population breeding science, biology and economics by adopting approaches of gene flow theory and ZPLAN specific software, studied the expected breeding achievements of the present breeding scheme, revealed the effects of population structure, employment years of bulls and breeding cows, opening level of nucleus population, population sizes and other factors on the comprehensive progress of population-based breeding, the generation intervals and breeding benefits, and worked out an optimized technical indexes for the systematic breeding for the purpose of improving the present breeding scheme.It can be concluded from all the studies here that:(1) It is worthwhile to adopt the population-based selection and breeding for ONBS in order to accelerate the improvement via selective breeding of Qinchuan beef cattle, make up the disadvantages of the closed nucleus breeding system (CNBS), fix the properties, and cultivate excellent individuals. The ONBS of Qinchuan beef cattle consists of three herds of animals in a pyramid-like structure, the nucleus herd on the top, the breeding herd in the middle and the improved herd at the bottom. The nucleus herd is a seed-stock herd composed of prepotent bulls and breeding cows, the breeding herd and the improved herd are individuals coming from the breeding flock and commercial flock, which passed the performance test.(2) In large population size, the maximal genetic progress can be made when the number of cattle in nucleus herd is 10% of the total population of the three groups under normal selection intensity. And the rate of genetic progress can be reached in an ONBS when half of the breeding cows come from fundamental group (the breeding herd together with the improved herd) and the nucleus herd accounts for 5%～10% of the total population.(3) The optimal proportion of breeding cows to be selected from the fundamental group increases parallely with the rise of the selection intensity of bulls but decreases with the increase of the selection intensity of breeding cows. Without confinement of the migratory direction of breeding cows and bulls, the maximal genetic progress can be realized when 50% replacement breeding cows and 5%～20% replacement bull of upper group come from the lower group and 50% replacement bull in lower group come from upper group.(4) The successive migration effects in ONBS usually result in the convergence of the gene frequencies, population means, population differences of subpopulation and total population and increase the homogeneity of total population. Compared with CNBS, ONBS can mitigate the prominent random fluctuation and sampling deviation of hereditary property in population originated from gamete sampling in the replication breeding of small population since ONBS shows special homogeneity effects in migration so maintain genetic homogeneity to total population in a progressive way. The united genetic effects of migration and selection of ONBS are usually advantageous over CNBS in the genetic progress.(5) According to analysis of a herd comprising 2500 breeding cows and within planned 20 years, the present breeding scheme is not in the optimal condition in population size, the proportion of breeding subgroups, utilization of bulls and cows and open level. The present breeding scheme can reach the following results in a calving cycle of each cow: the comprehensive breeding progress of 46.83 CNY, the breeding return of 214.75 CNY, the breeding input of 32.33 CNY, the breeding profit of 182.42 CNY, the generation interval of 5.26 years and the input/output ratio of 1:6.64. Therefore all the parameters can be improved greatly in comparison to international practices.(6) Ideal breeding profit and breeding progress can be made when the proportion of the selected calves is 0.6 and that of selected heifer is 0.8 in breeding program, and these measurements comply with the production practice.(7) It can be concluded from analysis that the ideal service life of the breeding animals in the optimized breeding program is one year of bulls and 5 to 6 years of cows, and one to two years of test bull and 4 to 5 years of test cows all in nucleus herd and breeding herd, and one year of bulls and 6 years of cows in improved herd.(8) The analysis of the optimized breeding program developed in this study showed an increase of the comprehensive breeding progress by 25%, an increase of breeding output by 37%, an increase of breeding profits by 42%, an increase of input/output ratio from 1:6.64 to 1:8.23, and a decrease of the generation interval by 15%, compared with the current breeding scheme.(9) Under the circumstances of limiting the proportion of nucleus herd and with the increase of the breeding population and the number of breeding cattle in nucleus herd, the breeding input (fixed capital) will decrease successively, but the comprehensive breeding progress, the breeding outcome and breeding profit will increase successively.(10) After the comprehensive analysis and optimization of all factors, the comprehensive breeding progress and the breeding profits will remain high in a breeding population of 2500 breeding cows if the proportion of the nucleus herd, the breeding herd and the improved herd is respectively 7%～9%, 11%～13% and 80% and the open level of the nucleus herd is lower than 20%. This study presumes that the ideal breeding profit will be reached if test bulls are in service for one year, the utilization lifespan of other bulls is 3 to 4 years, and this service lifespan of breeding cows is 5 years, all in the nucleus herd, and the ideal breeding profit will be gained if 20%～40% of the cows in improved herd are bred by bulls form nucleus herd. The optimal generation interval will be 4.05 years, the comprehensive breeding progress be 61.72 CNY, the breeding outcome be 306.61 CNY, the breeding profit be 270.83 CNY, reaching increases by 23%, 32%, 43% and 48% respectively in compared with the present breeding scheme. And input/output ratio of the optimized breeding system will be 1:8.56.更多还原