Ledur M C, Liljedahl L E, McMillan I, Asselstine L, Fairfull R W
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
Poult Sci. 2002 Oct;81(10):1439-47. doi: 10.1093/ps/81.10.1439.
Three White Leghorn strains, their two-way crosses, and two commercial lines were used to evaluate the effects of aging on heterosis (H), reciprocal effects, and additive (A), Z-chromosome (Z), and heterotic effects and their variances on egg quality traits during the first laying cycle. Egg weight (EW), specific gravity (SG), Haugh unit (HU), and albumen height (AH) were measured at 240, 350, and 450 d of age from hens housed one per cage in a randomized block design. The mean heterosis was significant over time only for EW. For EW, heterosis increased in magnitude with age. The mean heterosis for both HU and AH was also influenced by age. Reciprocal effects were significant, on average, across periods for all traits and were influenced by age. The age-related changes in additive, Z-chromosome, and heterotic effects varied significantly among strains, indicating differences by genetic group in response to aging for egg quality traits. The heterotic, environmental, and phenotypic variances increased with age for all traits, except for AH. The additive and Z-chromosome variances did not always increase with age. Their age trend varied, depending on the trait. Heritabilities decreased with advancing age, suggesting that selection to improve lifetime performance of egg quality traits can be done early in the cycle.
使用三个白来航鸡品系、它们的正反交组合以及两个商业品系，来评估衰老对杂种优势（H）、正反交效应以及加性效应（A）、Z染色体效应（Z）和杂种优势效应及其方差在首个产蛋周期内对蛋品质性状的影响。在240日龄、350日龄和450日龄时，对每笼饲养一只母鸡的蛋重（EW）、比重（SG）、哈夫单位（HU）和蛋白高度（AH）进行测量，采用随机区组设计。平均杂种优势仅在蛋重方面随时间显著变化。对于蛋重，杂种优势的幅度随年龄增加。哈夫单位和蛋白高度的平均杂种优势也受年龄影响。所有性状的正反交效应在各时期平均而言均显著，且受年龄影响。加性效应、Z染色体效应和杂种优势效应随年龄的变化在品系间差异显著，表明不同遗传组对蛋品质性状衰老的反应存在差异。除蛋白高度外，所有性状的杂种优势方差、环境方差和表型方差均随年龄增加。加性方差和Z染色体方差并非总是随年龄增加。它们随年龄的变化趋势因性状而异。遗传力随年龄增长而降低，这表明可以在产蛋周期早期进行选择，以提高蛋品质性状的终生性能。
