College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan, P. R. China 625014.
Poult Sci. 2012 Sep;91(9):2405-10. doi: 10.3382/ps.2012-02165.
Artificial selection in closed populations can fix or differentiate alternative alleles of loci associated with selected traits. Two closed chicken populations, A and B, originating from Jiuwu, a Chinese native breed, were bred for more than 10 generations. We compared progeny from reciprocal crosses (AB and BA) under free range (trial 1) and cage and pen (trial 2) systems. Traits measured included feed conversion, live BW, subcutaneous fat thickness, percentages of carcass, semi-eviscerated carcass, eviscerated carcass, breast muscle (pectoralis major and minor), leg muscle (boneless drum and thigh), heart, gizzard, proventriculus, liver, comb, and abdominal fat, plus moisture and fat content in breast muscle at 91 d. In trial 1, there were no significant differences between crosses for any trait except percentage proventriculus (AB > BA). Males were significantly heavier with greater proportions of semi-eviscerated carcass, leg muscle, heart, and comb than females, whereas females had thicker subcutaneous fat and higher percentage abdominal fat, breast muscle, gizzard, and proventriculus than males. In trial 2, chickens raised in cages were significantly heavier, had superior feed efficiency, thicker subcutaneous fat, higher fat content and percentage abdominal fat, carcass, semi-eviscerated carcass, liver, and comb than those reared in pens. Those reared in pens exhibited significantly greater proportions of breast muscle, gizzard, and proventriculus than those raised in cages. The only significant 2-way interaction was cross × sex for percentage semi-eviscerated and eviscerated carcass, because BA males were greater than other combinations. Interactions of cross × sex × housing system for percentage liver and abdominal fat were significant; cage-reared AB females displayed higher percentages than pen-reared BA males. Results implied that subpopulations should be considered rather than a single larger population as a way to reduce loss of genetic variation in local and heritage stocks. Although performance of reciprocal crosses was similar across housing systems, caging during the finishing stage of a slow-growing breed enhanced feed efficiency, BW, and meat composition.
人工选择可以在封闭群体中固定或分化与选择性状相关的基因座的替代等位基因。两个来自中国本土品种九圩鸡的封闭鸡群 A 和 B 经过 10 多代的选育。我们比较了自由放养（试验 1）和笼养（试验 2）系统下正反交（AB 和 BA）后代的表现。测量的性状包括饲料转化率、活体重 BW、皮下脂肪厚度、屠体率、半屠体率、屠体率、胸肌（胸大肌和胸小肌）、腿肌（去骨鸡腿和大腿）、心脏、肌胃、嗉囊、肝脏、鸡冠和腹部脂肪，以及 91 日龄胸肌的水分和脂肪含量。在试验 1 中，除了前胃比例（AB>BA）外，两个杂交组合在任何性状上都没有显著差异。公鸡比母鸡重，半屠体率、腿肌、心脏和鸡冠比例较高，而母鸡的皮下脂肪较厚，腹部脂肪、胸肌、肌胃和嗉囊比例较高。在试验 2 中，笼养鸡比平养鸡体重更大，饲料效率更高，皮下脂肪更厚，脂肪含量和腹部脂肪比例、屠体率、半屠体率、肝脏和鸡冠比例更高。平养鸡的胸肌、肌胃和嗉囊比例显著高于笼养鸡。唯一显著的 2 因素互作是杂交组合×性别对半屠体率和屠体率的影响，因为 BA 公鸡比其他组合更大。杂交组合×性别×饲养系统对肝脏和腹部脂肪比例的互作也很显著；笼养 AB 母鸡的肝脏和腹部脂肪比例显著高于平养 BA 公鸡。结果表明，应该考虑亚群而不是单一的更大群体，以减少地方品种和传统品种遗传变异的丧失。虽然正反交在不同的饲养系统中表现相似，但在生长缓慢的品种的育肥后期进行笼养可以提高饲料效率、体重和肉质组成。
