Chen C F, Tixier-Boichard M
Unité Mixte de Recherches Génétique et Divaersité Animales Institut National de la Recherche Agronomique/ Institut National Agronomique Paris-Grignon, 78352 Jouy-en-Josas Cedex, France.
Poult Sci. 2003 May;82(5):709-20. doi: 10.1093/ps/82.5.709.
Two dwarf brown-egg layer lines, differing in their genotype for the naked neck gene (NA), line L2 (NA*NA/NA) and line L1 (NAN/*N), have been selected for 16 generations for increased average clutch length. A control line from the same base population, dwarf and segregating for the NA gene, was maintained by random mating. Genetic parameters were estimated by a multivariate derivative-free restricted maximum likelihood procedure, and the NA gene effect was estimated within the unselected control line. The studied traits included clutch traits, egg production traits, abnormal eggs, egg weight at 36 wk, and BW at 42 wk. The average clutch length, egg number, and maximum clutch length were normalized using the Box-Cox transformation. In response to 16 generations of direct selection for increased average clutch length, other egg production traits, such as laying rate and total egg number, have been indirectly improved in a dwarf layer genetic background. The estimated heritabilities were 0.406 to 0.424 for transformed average clutch length (TCL), 0.373 to 0.411 for transformed egg number (TEN), 0.529 to 0.559 for age at first egg (AFE), 0.275 to 0.282 for laying rate (LR), 0.455 for dutch number (CN), and 0.319 for the number of double-yolked eggs (DYEN). The TCL had high genetic correlations with TEN (0.777), LR (0.863), maximum clutch length (0.902), and CN (-0.845). Selection for increased average clutch length was an effective method for increasing egg production. Line L2 showed a higher egg weight than L1, which indicates that the combined effect of NA and DW genes was favorable to maintain egg weight when egg number could be improved. Line L1 showed a higher number of DYEN, suggesting that the regulation of follicular maturation was changed in this line.
两个矮小型褐壳蛋鸡品系，裸颈基因（NA）的基因型不同，L2系（NA*NA/NA）和L1系（NAN/*N），为增加平均产蛋周期长度已进行了16代选育。从同一基础群体中选取一个矮小型且NA基因分离的对照品系，通过随机交配进行维持。通过多变量无导数限制最大似然法估计遗传参数，并在未选择的对照品系中估计NA基因效应。研究的性状包括产蛋周期性状、产蛋性状、异常蛋、36周龄时的蛋重以及42周龄时的体重。使用Box-Cox变换对平均产蛋周期长度、产蛋数和最长产蛋周期长度进行标准化。在对增加平均产蛋周期长度进行16代直接选择后，在矮小型蛋鸡遗传背景下，其他产蛋性状，如产蛋率和总产蛋数也得到了间接改善。转化后的平均产蛋周期长度（TCL）的估计遗传力为0.406至0.424，转化后的产蛋数（TEN）为0.373至0.411，开产日龄（AFE）为0.529至0.559，产蛋率（LR）为0.275至0.282，窝蛋数（CN）为0.455，双黄蛋数（DYEN）为0.319。TCL与TEN（0.777）、LR（0.863）、最长产蛋周期长度（0.902）和CN（-0.845）具有较高的遗传相关性。选择增加平均产蛋周期长度是提高产蛋量的有效方法。L2系的蛋重高于L1系，这表明NA和DW基因的联合效应在提高产蛋数时有利于维持蛋重。L1系的DYEN数量较多，表明该品系卵泡成熟的调节发生了变化。
