Effect of production system and flock age on eggshell and egg internal quality measurements

Abstract

Egg quality was measured in eggs from different flocks that were reared together and then allocated to different production systems. Eggs were processed for measurements of eggshell and egg internal quality variables, scoring of ultrastructural mammillary layer features, completeness of cuticle cover, and protoporphyrin IX (PP IX) quantification. There was a significant main effect (P < 0.05) of production system on shell reflectivity, egg weight, and egg internal quality and significant effects of flock age on most measurements. The mammillary layer ultrastructural variables showed no clear relationship with production system and flock age. However, there was a significant interaction between production system and flock age for mammillary cap, early and late fusions. Cuticle cover ( ΔE∗ab ), was significantly higher in barn eggs (19.20), followed by free range (17.57), and cage eggs (15.99). Completeness of cuticle cover was significantly higher in eggs from the 44 week old flock than for 64 week and 73 week old flocks. For eggshells with cuticle intact, there was a significant main effect of both production system and flock age, and significant interaction between the two, for shell reflectivity, L*a*b* values and amount of PP IX. For PP IX, when this difference was calculated for the cuticle alone, there were no statistically significant differences. In 1 g of shell with and without cuticle, there was more PP IX in cage eggs (9.49 × 10−8, 7.90 × 10−8 mM) followed by free range (8.24 × 10−8, 6.90 × 10−8 mM), and barn eggs (8.64 × 10−8, 7.28 × 10−8 mM). Similar trends were recorded for the amount of PP IX in 1 g of cuticle, but the difference was not statistically significant. The amount of PP IX decreased significantly with increasing flock age. Comparing the cage and barn production systems at 68 week of flock age, there was no difference for the amount of PP IX in shell with or without cuticle, or in the cuticle alone. Eggs from the cage production system were darker in color and contained more PP IX mainly within the calcareous part of the shell. For the barn production system, the completeness of cuticle cover was higher and egg weight generally lower.