The location of protoporphyrin in the eggshell of brown-shelled eggs

Abstract

Protoporphyrin has been identified as the main eggshell pigment in brown-shelled eggs. However, there has been some uncertainty concerning the distribution of the pigment within the shell (and cuticle) in brown-shelled eggs. Most previous studies have suggested that the bulk of the shell pigment is deposited in the cuticle of the shell. The present study measured the levels of protoporphyrin in intact eggshells and in shells from which the cuticle had been removed, using eggs from flocks at 3 different ages. This enabled the calculation of the relative amount of protoporphyrin in the calcareous eggshell and the cuticle layer of the eggshell. The majority of the protoporphyrin pigment was located in the calcareous part of the eggshell (80-87%) with a minority contained within the cuticle (13-20%). These findings suggest that studies focused on maintenance of shell color in brown-shelled eggs need to consider the stage of egg formation at which the reduction in pigment deposition is occurring.

A selection study for improving eggshell colour in two parent lines of laying hens and their hybrids

“…This indicated that hens lay small eggs with a darker eggshell colour but lay large eggs that are lighter coloured. These results were supported by similar studies by Odabasi et al (2007), Flock et al (2007), Cavero et al (2010), Cavero et al (2012), Lukanov et al (2015) and Samiullah and Roberts (2013). As a result of these selection studies on these newly developed breeding lines, shell colour will also be considered as a factor in the shell index values.…”

“…Research by Aygun (2013) stated that moulting stress has been shown to severely affect eggshell colour once the hen resumes laying, with the extent of the response differing among individual hens. A study by Samiullah and Roberts (2013) researched 33-, 50-and 67-week-old HyLine Brown hens to determine the amount of protoporphyrin IX in the eggshells. The amount of protoporphyrin IX in 1 g of whole eggshell was not significantly different, but in the cuticle itself, was found to be significantly higher in eggs from 50-week hens as compared with the 33-and 67-week hens.…”

Downregulation of ALAS1 by nicarbazin treatment underlies the reduced synthesis of protoporphyrin IX in shell gland of laying hens

“…The L* measurements represent the intensity of brown eggshell colour; the higher the value, the lighter the colour of the eggshell. Egg weight was measured using an analytical balance, and the eggs were further processed for protoporphyrin IX (PP IX) quantification following the method of Samiullah and Roberts 15 . The post-oviposition times (time-points) were 2, 5, 15 and 23.5 hrs for the four groups of hens selected.…”

“…Standard dilutions (0 to 6.87 nMoles) prepared from protoporphyrin IX di-sodium salt (Sigma Aldrich, Australia) were read at the same wavelength in order to construct a standard curve for the calculations of the amount of PP IX per gram of tissue. The quantification of PP IX in the eggshells was performed according to Samiullah and Roberts 15 .…”

“…The brown eggshell colour in laying hens is mainly due to the deposition of a pigment known as protoporphyrin IX (PP IX) during eggshell formation in the shell gland. The presence of PP IX in various shell layers has been reported 12–14 although most of the pigment is deposited into the outmost layers of the palisade layer (80–87%) with a smaller amount in the cuticle (13–20%) 15 . Shell deposition increases regularly 12–23 hrs post-oviposition and reaches a plateau 1.5 hrs before oviposition 16 , which coincides with the deposition of cuticle (1–1.5 hrs) 17 .…”