Hocking P M, Gavora J S, Chambers J R, Fortin A
Poult Sci. 1985 Jan;64(1):6-28. doi: 10.3382/ps.0640006.
Genetic variation for more than 40 traits was assessed in 26 stocks of mature chickens reared together and fed ad libitum from hatching to slaughter at 507 days of age. There was greater genetic variation among males than among females. The intraclass correlation, t, was high (greater than .75) for measures of size and weight and moderate (.20 to .60) for most other traits (P less than .05) including a measure of lean distribution (.37). Three main categories of stocks were studied, viz. outbred Leghorns, medium-sized stocks, and contemporary heavy meat chickens. Differences in lean distribution were not associated with category, but differences of 40 to 50 g/kg lean in the breast of some stocks may be caused by a single gene. Lean:bone ratios were similar in medium and heavy stocks but were greater (P less than .05) in heavy meat-types compared with outbred Leghorns. Bone density was higher (P less than .01) in females compared with males and in outbred Leghorns compared with heavier stocks (P less than .01). Heavy meat-type males were leaner (P less than .01) and had proportionately less fat in the abdominal cavity than outbred Leghorns. Carcass fatness was similar among stocks of females, but abdominal fat was lower in Leghorns selected for high egg production compared with unselected Leghorns (P less than .05) and heavy stocks (P less than .001). One resistant and two Marek's disease-susceptible stocks were replicated in a specific pathogen-free (SPF) environment. Spleen weight was larger (P less than .001) in the conventional environment. Females were relatively smaller (P less than .05) than males in the conventional environment. Body temperature (t = .25, P less than .05) and feed intake were assessed in males. Heavy meat birds had a lower (P less than .01) body temperature than outbred Leghorns and medium-sized stocks. Differences among stocks for feed intake (t = .77) were significant (P less than .05); however, they were greatly reduced when feed intake was expressed as g/kg liveweight (LW) (t = .49) or g/kg LW.75 (t = .25). Outbred Leghorns ate less in absolute terms but significantly more (P less than .01) as a proportion of LW or LW.75 than the medium and heavy lines.
在26组共同饲养的成年鸡群中评估了40多种性状的遗传变异，这些鸡从孵化到507日龄屠宰一直自由采食。雄性之间的遗传变异比雌性更大。对于大小和重量的测量，组内相关系数t较高（大于0.75），而对于大多数其他性状（P小于0.05），包括瘦肉分布测量值（0.37），该系数为中等（0.20至0.60）。研究了三类主要鸡群，即远交来航鸡、中型鸡群和现代重型肉鸡。瘦肉分布的差异与类别无关，但某些鸡群鸡胸肉中瘦肉含量每千克相差40至50克可能是由单个基因引起的。中型和重型鸡群的瘦肉与骨骼比例相似，但与远交来航鸡相比，重型肉鸡的该比例更高（P小于0.05）。与雄性相比，雌性的骨密度更高（P小于0.01）；与较重的鸡群相比，远交来航鸡的骨密度更高（P小于0.01）。重型肉鸡雄性比远交来航鸡更瘦（P小于0.01），腹腔内脂肪比例更低。雌性鸡群的胴体脂肪含量相似，但与未选的来航鸡（P小于0.05）和重型鸡群（P小于0.001）相比，选作高产蛋量的来航鸡腹部脂肪含量更低。在无特定病原体（SPF）环境中复制了一组抗性鸡群和两组马立克氏病易感鸡群。在常规环境中，脾脏重量更大（P小于0.001）。在常规环境中，雌性相对比雄性小（P小于0.05）。对雄性鸡的体温（t = 0.25，P小于0.05）和采食量进行了评估。重型肉鸡的体温比远交来航鸡和中型鸡群更低（P小于0.01）。鸡群之间采食量的差异（t = 0.77）显著（P小于0.05）；然而，当采食量以克/千克活重（LW）（t = 0.49）或克/千克LW.75（t = 0.25）表示时，差异大幅减小。远交来航鸡的绝对采食量较少，但相对于活重或LW.75的比例显著更高（P小于0.01），高于中型和重型品系。
