Pig breeding is generally conducted among many herds, so EBV comparisons across populations are necessary. Genetic connectedness is required for reliable between-farm animal EBV comparisons. Five quantitative overall connectedness measures among populations have been proposed so far, coefficient of connectedness(γ*), coefficient of determination (CD) and overall indices of precision, connectedness rating, number of direct genetic links between subpopulations due to common sires and dams (GLt), and average genetic covariance (AGC) are reviewed and their properties are discussed in this paper. It is recommended to use AGC at present for measuring genetic connectedness between herds.

A resource population constructed by F2 design with Landrace and Chinese indigenous Lantang pigs was used in this study. Seven microsatellite DNA markers on chromosome 6 and USDA2.6 pig genetic linkage map were used for interval QTL mapping. The results revealed that at the position of 38-41 cM there was a chromosome-wide highly significant QTL affecting carcass backfat A thickness (P<0.01), which was closely linked with MN007 and the ratio of QTL additive variance to F2 phenotypic variance was 5.90%. At the position of 60-70 cM there were two chromosome-wide significant QTLs affecting carcass lean percentage (P<0.01) and skin and fat percentage (P<0.05), which were closely linked with MN003 and the ratio of QTL additive variance to F2 phenotypic variance were 18.44 and 3.75%, respectively. At the same position, there was a single-point QTL also closely linked with MN003 and highly significantly (P<0.01) affecting carcass lean. In addition, there were two chromosome-wide highly significant (P<0.01) QTLs affecting meat color and marbling, which were closely linked with MN13 at the position of 70-75 cM and the ratio of QTL additive variance to F2 phenotypic variance were 14.05 and 1.77%, respectively.

保种与选育有机结合是解决我国丰富的畜禽品种遗传资源保存的一个重要的有效手段。本文探讨在保种目标性状明确的情况下，如何利用通用选择指数灵活方便地制定选择标准，以达到保种与选育相结合的目的。并以良种细毛羊的选育为例，确定了在保证羊毛质量不下降的基础上，充分利用各种信息来源评定个体的综合育种值，达到尽量提高羊毛产量的目的。此外，探讨了在保种目标的约束下主攻净毛量等，以及当保种性状也需改进时的选择方法，为保种与选育相结合探索一条可行的途径。

供试鸡为30只AA肉仔鸡，其中公、母仔鸡各15只。测定49日龄活重、屠体重、腹脂重、腹脂率、肝脏鲜重、干肝脂肪含量、胸肌干样脂肪含量和血浆VLDL浓度。采血分离出DNA后，对公、母鸡群分别利用已筛选出的17个随机引物分别对所有个体的基因组进行PCR扩增。对多态性片段，将“有带”、“无带”个体组成的群体看作是独立样本，比较两样本间数量性状的差异。结果在公、母鸡群分别发现了29、35个显著关联的标记与性状组合。经对与同一标记同时关联的性状间的相关分析及两样本间个体表型值分布的分析，发现上述大部分标记与性状关联是不可信的。在公鸡群没有发现显著的标记与性状关联，在母鸡群检测到两个显著的标记与性状关联，它们是OP13082腹脂重和OP13082腹脂率。

利用高度选育的8头瘦肉型长白猪为父本，16头中国优良地方品种蓝塘猪为母本，采用远交系杂交的F，代设计方法，建立包括8头F，公猪、40头F，母猪和232头F，个体的猪资源群体。资源群体的遗传分析表明，所测定的32个性状都有一定的变异，主要经济性状的变异系数都在10%以上。进一步的方差组分估计表明，主要经济性状的加性遗传方差较大。在所测定6号染色体连锁群的22个微卫星DNA标记中，12个表现有多态性，全群平均杂台度为0.53，多态信息含量为0.46，能较好地为QTL检测提供信息。因此，F2代有较好的分离状态，有可能利用该资源群体检测到较多的QTL。

以白羽肉仔鸡为研究材料，应用随机扩增多态DNA（RA PD）技术，利用已筛选出的17个随机引物对15个公仔鸡和15个母仔鸡个体间的遗传变异进行分析，实验结果表明，（1）17个引物在母鸡群共产生145个扩增片段，其中有102个是多态性片段，多态率为70134%；17个引物在公鸡群共产生了154个扩增片段，其中有92个是多态性片段，多态率为59174%。这些结果说明RA PD标记的多态性较高，作为一种DNA 标记，它可以用于分析鸡群体的遗传结构；（2）公、母鸡群体内个体间的遗传相似系数分别为018621，018214；（3）可以利用RA PD技术检测肉鸡杂合群体内个体间的遗传变异程度，但必须使用大量的随机引物。