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 d. 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 h after lights on. Differences in oviposition time between lines were significant (P=0.025). Oviposition interval was slightly greater than 24 h at 24:06 h:min with significant differences between lines (P = 0.003). The variance was low and the maximum difference between lines for oviposition interval was only 11 min. 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 seven eggs (24:01 h:m) than those laying six (24:08) or five eggs (24:14).5. There was a significant positive association between cuticle deposition and oviposition interval (P = 0.007) with a minimal 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 interval and was not different from zero 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 h, but it seems unlikely that it was a major component.