Campo J L, Carnicer C
Departamento de Producción Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain.
Poult Sci. 1993 Dec;72(12):2193-9. doi: 10.3382/ps.0722193.
Fearfulness was measured as latency to recover from induced tonic immobility using White Leghorn hens from a population originated by crossing three different strains selected for egg number and egg weight. Realized heritability was calculated in a single generation selection experiment with eight replicates, each consisting of 76 40-wk-old females from which 21% were selected for decreased tonic immobility duration. A randomly selected control population was maintained for each replicate. Separately from this experiment, fear differences between ages and sexes were investigated at 1, 2, 4, 8, 12, 16, 20, 24, 28, and 32 wk. The realized heritability (.32 +/- .10) indicates that induced tonic immobility should respond to selection. It was numerically higher than the estimate calculated by half-sib analysis of variance in the base population (.18 +/- .07); the logarithmic transformation did not yield higher heritability estimates. Crossing effects were evaluated in two different crossbreds, i.e., Leghorn x Castellana and Buff Prat x White Prat, which suggested important negative heterotic effects for this fear-related trait (-31% and -54%, respectively). Significant (P < .05) quadratic and cubic variation between 1 and 32 wk of age was obtained in females and males, respectively; the involvement of these age effects make it difficult to generalize about realized heritability for tonic immobility. Tonic immobility increased from 32 to 72 wk. Differences between the sexes were apparent, males showing longer tonic immobility durations than females except in the postjuvenile period before sexual maturity, suggesting a relationship between this trait and hormonal changes.
恐惧程度通过使用来自一个由三个不同品系杂交培育的群体中的白来航母鸡，测量其从诱导性强直性静止中恢复的潜伏期来衡量。这三个品系是为蛋数和蛋重而选择的。在一个单代选择实验中计算了实现遗传力，该实验有八个重复，每个重复由76只40周龄的雌性组成，从中选择21%以缩短强直性静止持续时间。每个重复都维持一个随机选择的对照群体。与该实验分开，在1、2、4、8、12、16、20、24、28和32周龄时研究了年龄和性别之间的恐惧差异。实现遗传力（0.32±0.10）表明诱导性强直性静止应对选择作出反应。其数值高于基础群体中通过半同胞方差分析计算的估计值（0.18±0.07）；对数转换并未产生更高的遗传力估计值。在两个不同的杂交组合中评估了杂交效应，即来航×卡斯特拉纳和布夫普拉特×白普拉特，这表明该与恐惧相关的性状存在重要的负杂种优势效应（分别为-31%和-54%）。在1至32周龄之间，雌性和雄性分别获得了显著（P<0.05）的二次和三次变化；这些年龄效应的存在使得难以概括强直性静止的实现遗传力。强直性静止从32周龄增加到72周龄。性别之间的差异很明显，除了性成熟前的幼年期外，雄性的强直性静止持续时间比雌性长，这表明该性状与激素变化之间存在关系。
