Is oviposition time and oviposition interval associated with the deposition of cuticle on the hen’s egg?

1) The cuticle acts as a barrier to prevent microbial penetration of the eggshell. The reduction in the oviposition interval with selection for egg production and the activity of clock genes in the oviduct led to testing the hypothesis that the interval between successive oviposition of eggs would be related to the deposition of the cuticle. 2) There was oviposition interval and cuticle deposition data from 2140 eggs from 5 White Leghorn pure lines for over 7 days. The association between oviposition interval and cuticle deposition was assessed using a random slopes model for each hen. 3) The time of oviposition was 05:37 h:m, about 2.5 hours after lights on. Differences in oviposition time between lines were significant (P=0.025). Oviposition interval was slightly greater than 24 hours at 24:06 h:m with significant differences between lines (P=0.003). The variance was low and the maximum difference between lines for oviposition interval was only 11 minutes. Cuticle deposition was 28.87ΔE∗ab with no differences between lines. 4) The number of eggs a hen laid had an effect on the oviposition interval (P=0.004), being shortest in hens laying 7 eggs (24:01) than those laying 6 (24:08) or 5 eggs (24:14). 5) There was a significant positive association between cuticle deposition and oviposition interval (p=0.0073) with a with a modest increase of 0.79 ΔE∗ab in cuticle deposition for each additional hour of oviposition interval. Heritability for cuticle deposition in this study was 0.48 but heritability was not measurable for oviposition time. 6) Combined with a difference between the top and tail of the distribution for cuticle deposition, there was evidence for a significant but relatively small relationship between oviposition interval and deposition of cuticle on the egg. This may have contributed to some reduction in cuticle coverage as the oviposition interval approached 24 hours, but it seems unlikely that it was a major component.

1) 蛋壳角质层（cuticle）可作为屏障，阻止微生物穿透蛋壳。鉴于选育产蛋性能可缩短产卵间隔（oviposition interval），且输卵管（oviduct）内存在时钟基因（clock genes）的表达活性，本研究据此验证假说：连续产卵的间隔与角质层沉积存在关联。 2) 本研究收集了5个白来航纯系（White Leghorn pure lines）共2140枚鸡蛋的产卵间隔与角质层沉积数据，采样时长超过7天。研究针对每只母鸡采用随机斜率模型（random slopes model），分析产卵间隔与角质层沉积之间的关联。 3) 产卵时间约为开灯后2.5小时，具体时刻为05:37时:分。不同纯系间的产卵时间差异具有统计学意义（P=0.025）。产卵间隔略高于24小时，均值为24:06时:分，不同纯系间的差异同样具有统计学意义（P=0.003）。该指标的方差较低，不同纯系间产卵间隔的最大差值仅为11分钟。蛋壳角质层沉积量为28.87ΔE*ab，不同纯系间无显著差异。 4) 母鸡的产蛋数量对产卵间隔存在显著影响（P=0.004）：产7枚蛋的母鸡产卵间隔最短（24:01时:分），短于产6枚（24:08时:分）或产5枚（24:14时:分）的母鸡。 5) 角质层沉积量与产卵间隔之间存在显著的正相关关系（p=0.0073）：产卵间隔每增加1小时，角质层沉积量会小幅提升0.79ΔE*ab。本研究中角质层沉积量的遗传力（heritability）为0.48，但产卵时间的遗传力无法测算。 6) 结合角质层沉积量分布的首尾端差异，本研究证实产卵间隔与蛋壳角质层沉积之间存在显著但程度较弱的关联。当产卵间隔接近24小时时，该关联可能会导致角质层覆盖度出现一定程度的下降，但并非其主要影响因素。