Relationships between age, shell quality and individual rate and duration of shell formation in domestic hens

Abstract

Abstract 1. The duration and rate of shell formation was measured individually in each of 44 hens. Comparisons were made between hens of different ages, and also between hens which laid eggs of differing shell qualities. 2. Shell formation began 9–5 to 11 h after the oviposition of the previous egg, increased linearly for 13 h and then plateaued at 1–5 h before oviposition. 3. The variation in egg shell quality observed in two experimental groups of hens was 75% attributable to differences in the rate of shell deposition and 25% attributable to difference in the duration of shell deposition. 4. The mean interval between ovipositions increased with age but neither shell weight, nor rate or duration of shell depositon were affected. The increase in egg weight with age accounted for the decrease in shell quality. 5. Intervals between ovipositions were positively correlated with the duration of shell formation, especially its latter stages. 6. Egg production was negatively correlated with the interval between ovipositions but not with the duration or rate of shell deposition. There was a negative correlation between duration and rate of shell deposition, except in the case of the hens producing eggs of poor shell quality.