Velleman S G, Coy C S, Anderson J W, Patterson R A, Nestor K E
Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio 44691, USA.
Poult Sci. 2003 Sep;82(9):1365-72. doi: 10.1093/ps/82.9.1365.
The inheritance of, and effect of selection for increased BW on, measurements of muscle fibers and extracellular space in turkeys were studied using a randombred control line (RBC2), a subline (F) of RBC2 selected long-term only for increased 16 wk BW, a commercial sire line (B), and reciprocal crosses of the F and B lines. Measures of additive genetic variation were obtained by comparing all of the pure lines or just the large-bodied F and B lines. Estimates of nonadditive genetic variation were obtained by contrasting the average of the reciprocal crosses with the average of the parental lines. A contrast of the reciprocal crosses provided estimates of sex linkage or maternal effects. Samples of pectoralis major muscle were obtained from three males and three females of each genetic group at 1, 4, 8, and 16 wk of age in a manner to avoid muscle contraction. After fixing and cross sectioning, the muscle samples were stained with hematoxylin and eosin to view muscle morphology. The stained sections were analyzed for muscle fiber width, muscle fiber bundle width (except at 16 wk of age), number of fibers within a 136-microm2 area, and extracellular matrix perimysial (PW) and endomysial (EW) width. Additive genetic variation, as measured by line differences, of measures of muscle fibers and extracellular matrix was a more important source of variation when the RBC2 line was included in the comparison. When all of the pure lines were compared, line differences were significant for fiber bundle width at 4 wk of age; individual fiber width and number of fibers in a given area at 4, 8, and 16 wk of age; PW at all ages; and EW at 1, 8, and 16 wk of age. With the possible exception of PW, nonadditive genetic variation was not an important source of variation for muscle measurements. For PW, the estimates of heterosis were -14.6, 26.4, 14.5, and 17.3% at 1, 4, 8, and 16 wk of age, respectively, but none of the values was significant (P > 0.05). Genetic increases in BW were associated with an increase in muscle fiber width, a smaller number of fibers in a given area, and less extracellular space at older ages. Apparent differences in growth patterns among the genetic groups may have been responsible for the different patterns of change in muscle measurements in the various genetic groups over ages.
利用一个随机交配对照品系（RBC2）、仅长期选择提高16周龄体重的RBC2亚系（F）、一个商业父本品系（B）以及F系和B系的正反交组合，研究了火鸡体重增加的遗传方式以及选择增加体重对肌肉纤维和细胞外间隙测量值的影响。通过比较所有纯系或仅比较大体型的F系和B系来获得加性遗传变异的测量值。通过对比正反交组合的平均值与亲本系的平均值来获得非加性遗传变异的估计值。正反交组合的对比提供了性连锁或母体效应的估计值。在1、4、8和16周龄时，从每个遗传组的三只雄性和三只雌性中获取胸大肌样本，取样方式避免肌肉收缩。固定和横切后，肌肉样本用苏木精和伊红染色以观察肌肉形态。对染色切片分析肌肉纤维宽度、肌肉纤维束宽度（16周龄时除外）、136平方微米区域内的纤维数量以及细胞外基质肌束膜（PW）和肌内膜（EW）宽度。当比较中包括RBC2品系时，由品系差异测量的肌肉纤维和细胞外基质测量值的加性遗传变异是更重要的变异来源。当比较所有纯系时，4周龄时纤维束宽度的品系差异显著；4、8和16周龄时单个纤维宽度和给定区域内的纤维数量；各年龄的PW；以及1、8和16周龄时的EW。除PW外，非加性遗传变异不是肌肉测量变异的重要来源。对于PW，1、4、8和16周龄时杂种优势的估计值分别为-14.6%、26.4%、14.5%和17.3%，但这些值均不显著（P>0.05）。体重的遗传增加与肌肉纤维宽度增加、给定区域内纤维数量减少以及老龄时细胞外间隙减少有关。各遗传组生长模式的明显差异可能是不同遗传组在不同年龄阶段肌肉测量变化模式不同的原因。
