Intra-Clutch Changes in Egg Composition and Shell Quality in Laying Hens.

Intra-clutch changes in egg composition and shell quality were examined using two laying hen strains (High line: 40 hens, Low line: 39 hens) which were developed by a divergent selection for yolk-albumen ratio. Oviposition time was recorded every 30 minutes from 5: 30 to 18: 30 for a duration of 90 days at about 270 days of age. The eggs of individual hens were collected every day from three consecutive clutches. Only the hens that formed the clutches determined apparently by their oviposition time were used for the analyses. Statistical analyses were performed separately for the four clutch size groups.The lag in oviposition time was the longest for the last egg of the clutch (terminal egg). There was no difference in the oviposition interval between lines. The changes in egg weight of consecutive eggs within a clutch showed that the first egg of the clutch was the heaviest and then the weight gradually decreased. The decrease in weight the low line was estimated to be 3.0-4.0g, or 6% of the 1st egg, while the decrease in weight in the high line was 1.5-2.0g (4% of the first egg). The yolk weight of the 2nd egg was heavier than that of other eggs in the same clutch, and decreased by 1.0-1.5g in both lines. Albumen weight showed a remarkable decrease from the first egg to the 3rd or the 4th eggs of the clutch, then the decrease tended to be smaller. The decrease in the low line, which had a larger amount of albumen, was estimated to be larger. Thick albumen weight tended to decrease as the serial number within a clutch increased. However, thin albumen weight increased slightly in eggs laid at later positions of the clutch. Egg-shell weight, thickness and strength showed a clear increase in the terminal egg of the clutch.