Eggshell Color Research Articles

Egg discrimination along a gradient of natural variation in eggshell coloration.

Accurate recognition of salient cues is critical for adaptive responses, but the underlying sensory and cognitive processes are often poorly understood. For example, hosts of avian brood parasites have long been assumed to reject foreign eggs from their nests based on the total degree of dissimilarity in colour to their own eggs, regardless of the foreign eggs' colours. We tested hosts' responses to gradients of natural (blue-green to brown) and artificial (green to purple) egg colours, and demonstrate that hosts base rejection decisions on both the direction and degree of colour dissimilarity along the natural, but not artificial, gradient of egg colours. Hosts rejected brown eggs and accepted blue-green eggs along the natural egg colour gradient, irrespective of the total perceived dissimilarity from their own egg's colour. By contrast, their responses did not vary along the artificial colour gradient. Our results demonstrate that egg recognition is specifically tuned to the natural gradient of avian eggshell colour and suggest a novel decision rule. These results highlight the importance of considering sensory reception and decision rules when studying perception, and illustrate that our understanding of recognition processes benefits from examining natural variation in phenotypes.

Influence of eggshell colour on egg yolk antibody level, incubation results, and growth in broiler breeders

ABSTRACT This study was performed to determine the effect of shell colour in eggs acquired from Ross-308 broiler breeders on the interior and exterior quality of the egg, the antibody content of the egg yolk, and growth performance. The shell colours of a total of 1350 eggs were classified, using a colorimeter, into three groups: dark (E67). The difference between groups with respect to egg weight, shape index, shell weight, and Haugh unit value was significant. Egg yolk antibody content [...]

Eggshell coloration and its importance in postmating sexual selection.

Avian eggshell color seems to fulfill multiple functions, some of them being structural and others signaling. In this study, we tested whether or not eggshell coloration may play a role in sexual selection of Tree Sparrows (Passer montanus). According to the “Sexually selected eggshell coloration” hypothesis, eggshell coloration signals female, egg or chick quality and males adjust parental investment according to this signal. Eggs of this species are covered with brown spots and patches, and variation between clutches is high. We found that eggshell coloration correlates with both protoporphyrin and biliverdin, but protoporphyrin concentrations are ten times higher. Eggshell coloration reflects egg and offspring quality, but not female quality. Thus, eggshell coloration may signal female postmating investment in offspring rather than female quality. Furthermore, differential allocation in terms of maternal investment is supported by the fact that females lay more pigmented clutches when mated to males with bigger melanin‐based ornaments relative to their own. Moreover, males invested proportionally more to chicks that hatched from more pigmented clutches. Our correlative results thus seem to support a role of sexual selection in the evolution of eggshell coloration in birds laying brown eggs, pigmented mainly by protoporphyrin.

Quantifying biliverdin in liver and spleen samples from multiple avian species

ABSTRACT Avian eggshells exhibit a variety of colors and patterns whose functions include camouflage, detection of brood parasites, and facilitation of embryonic development. In addition, eggshell coloration, specifically blue-green coloration, may signal a female's quality to her mate. This signaling hypothesis relies on the assumption that biliverdin, the pigment responsible for blue-green eggshell coloration, is an indicator of female quality. Biliverdin is the product of heme degradation and has antioxidant and immunomodulating properties, supporting the possibility that if only a limited amount of biliverdin can be produced, deposition of this pigment into eggshells may be costly to females. However, these putative physiological functions of biliverdin were established by mammal-based studies, even though mammals produce an enzyme—biliverdin reductase—that readily converts biliverdin into bilirubin. Thus, the assumed physiological properties of biliverdin stem from data based on the end-product bilir...

Effect of egg weight and amount of protoporphyrin and biliverdin in the egg shell on hatching characteristics and embryonal mortality in pheasants (Phasianus Colchicus)

This study was performed to investigate the effects of egg weight and amount of protoporphyrin and biliverdin in the eggshell on hatchability and embryonic mortality in pheasants. A total of 1908 eggs obtained from 48 weeks old pheasants were used in the study. The eggs were divided into three colour groups (dark brown, light brown and green) and two weight groups (up to 32 g and above 32 g). For the weight groups, there were significant differences in the hatchability of fertile eggs (P<0.01) and late period embryonic mortality (LPEM) (P<0.05). The highest hatchability of fertile eggs and the lowest embryonic mortality were determined in light eggs (≤32 g). In terms of eggshell colour groups, there were significant differences in the hatchability of total eggs (P<0.01); hatchability of fertile eggs (P<0.01); and early (P<0.01), middle (MPEM) (P<0.05) and late period (P<0.05) embryonic mortality. In present study, the highest hatchability and the lowest embryonic mortality rate (except for MPEM) were in the dark brown eggshell group. For all groups, the differences in fertility rate were insignificant (P>0.05). The highest hatching characteristics and the lowest embryonic mortality rates were determined in the dark brown eggs. Based on these results, to achieve higher a hatchability of total eggs, hatchability of fertile eggs and a lower embryonic mortality rate, it may be beneficial selection of dark brown pheasant eggs

SpotEgg: an image‐processing tool for automatised analysis of colouration and spottiness

Colouration and patterning are widespread amongst organisms. Regarding avian eggs, colouration (reflectances) has been previously measured using spectrometers whereas spottiness has been determined using human‐based scoring methods or by applying global thresholding over the luminance channel on photographs. However, the availability of powerful computers and digital image‐processing algorithms and software offers new possibilities to develop systematised, automatable, and accurate methods to characterise visual information in eggs. Here, we provide a computing infrastructure (library of functions and a graphical user interface) for eggshell colouration and spottiness analysis called SpotEgg, which runs over MATLAB. Compared to previous methods, our method offers four novelties for eggshell visual analysis. First, we have developed a standardised non‐human biased method to determine spottiness. Spottiness determination is based on four parameters that allow direct comparisons between studies and may improve results when relating colouration and patterning to pigment extraction. Second, researcher time devoted to routine tasks is remarkably reduced thanks to the incorporation of image‐processing techniques that automatically detect the colour reference chart and egg‐like shapes in the scene. Third, SpotEgg reduces the errors in colour estimation through the eggshell that are created by the different angles of view subtended from different parts of the eggshell and the optical centre of the camera. Fourth, SpotEgg runs automatic Fractal Dimension analysis (a measure of how the details in a pattern change with the scale at which this pattern is measured) of the spots pattern in case researchers want to relate other measurements with this special spatial pattern. Finally, although initially conceived for eggshell analysis, SpotEgg can also be applied in images containing objects different from eggs as feathers, frogs, insects, etc., since it allows the user to manually draw any region to be analysed making this tool useful not only for oologist but also for other evolutionary biologists.

Effect of Feeding and Withdrawal of Vanadium and Vitamin C on Egg Quality and Vanadium Residual Over Time in Laying Hens

This experiment examined the egg quality of hens fed vanadium (V) and vitamin C (VC) during storage, as well as the V and VC withdrawal on egg quality and V residual in egg. A total of 360 laying hens (31weeks old) were randomly allotted into a 3×2 factorial arrangement treatments (6 replicates and 10 chicks per replicate) with three levels of dietary V (0, 5, and 10mg/kg) and two levels of VC (0 and 100mg/kg) for 19weeks (feeding V and VC 12weeks, recovery 7weeks). The V residual in eggs at 4, 8, and 12th weeks were increased (linear effect, P≤0.01) as V levels increased and was not detected in albumen at 7th week after V withdrawal. Followed by 12-week feeding period, albumen height and Haugh unit of eggs during 2-week storage were decreased (linear and quadratic effect, P<0.01) by dietary V supplementation. Lightness value was increased (linear effect, P<0.01), whereas redness and yellowness value of the eggshell were lowered (linear effect, P<0.01) in V-containing diet. During 7-week withdrawal period, eggs from groups pre-feeding 5 and 10mg/kgV had lower (linear effect, P<0.01) overall albumen height and Haugh unit. The reducing effect on albumen height and HU continued to be observed until the seventh week, whereas the bleaching effect on eggshell color disappeared after 1-week withdrawal. The results indicated that feeding 5 or 10mg/kg V increases egg V residual and reduces egg albumen quality and bleached the shell color, and the impaired albumen quality induced by 10mg/kg of V lasted at least 6weeks after changing to no V supplementation diet. The addition of VC did not show to affect egg quality during storage or recovery phase.

Biliverdin- and protoporphyrin-based eggshell pigmentation in relation to antioxidant supplementation, female characteristics and egg traits in the canary (Serinus canaria)

Avian eggs exhibit a large variability in coloration and patterns, which are produced by blue-green biliverdin and red-brown protoporphyrin pigments. Several hypotheses have been proposed to explain the function of eggshell coloration. In this experimental study, we tested two hypotheses (signalling-function hypothesis and structural-function hypothesis) on both eggshell pigment types in an open-nesting songbird, the canary (Serinus canaria). Also, we aimed to examine whether deposition of pigments into the eggshell has any cost in terms of the plasma oxidative status of the female. We found that eggshell average blue-green chroma was increased by antioxidant supplementation, although we note that there had already been a pre-existing bias in plasma antioxidant capacity between the supplemented and control groups. Eggshell average blue-green chroma was positively related to female body condition during egg laying. However, blue-green eggshell colour was not related to female oxidative status during or after the laying period, and blue-green chroma increased with laying order. Accordingly, we found some support for that eggshell blue-green colour could reflect maternal antioxidant availability and body condition, but did not find evidence that it has a cost for the female’s oxidative status. By contrast, eggshell spot brightness was positively related to body condition, suggesting that darker spotting reflected poorer nutritional condition in the canary. Eggshell blue-green pigmentation was not significantly connected to the egg volume or yolk antioxidant level, but we found that eggs with lower yolk antioxidant concentration had higher average eggshell brown chroma. In sum, our results suggest that eggshell colour reflected female antioxidant and nutrient availability. Finally, we found that eggs with thinner eggshells had a more aggregated spot distribution, supporting the view that aggregated spots may help to strengthen eggshells. Avian eggs have a large variability in colours and patterns, which are due to two pigments: the blue-green biliverdin and the red-brown protoporphyrin. In this study, we tested whether eggshell pigmentation, measured by a spectrophotometer, could reflect female and egg quality in the canary, an open nesting songbird. We found that females supplemented with antioxidants before and during egg-laying laid more intense blue-green eggs. Females in better body condition laid eggs that had a more intense blue-green coloration, but lower intensity of brown coloration. Egg yolk antioxidant level was lower in eggs with more intense brown eggshell coloration. These results suggest that eggshell coloration could reflect the antioxidant and nutrient availability of females. Moreover, we found that eggs with thinner eggshells had a more aggregated spot distribution on the eggshell, supporting the view that aggregated brown pigment spots may help to strengthen eggshells.

Infectious bronchitis virus and brown shell colour: Australian strains of infectious bronchitis virus affect brown eggshell colour in commercial laying hens differently

ABSTRACTThe aim of the current study was to assess any effect of wild and vaccine Australian infectious bronchitis virus (IBV) strains on shell colour in brown-shelled eggs. In Experiment 1, eggs were collected from day 1 to day 13 post-inoculation (p.i.) from unvaccinated laying hens challenged with IBV wild strains T and N1/88 and from a negative control group of hens. In Experiment 2, eggs were collected from 2 to 22 days p.i. from unvaccinated and vaccinated laying hens challenged with either a wild or a vaccine strain of IBV. In Experiment 1, there was a significant effect (P < 0.05) of day p.i. and of viral strain on shell reflectivity, L* and protoporphyrin IX (PP IX) in eggshells, with and without cuticle. The mean PP IX/g of shell with and without cuticle was significantly higher on day 1 p.i. compared to day 7, after which PP IX increased with day p.i. In Experiment 2, shell reflectivity and L* increased and PP IX decreased with increased day p.i. until day 12. Shell reflectivity and L* decreased slightly after day 12 and increased again towards day 22. Shell reflectivity, L* and PP IX were not significantly different for eggshells from unvaccinated and vaccinated laying hens in the intact eggshell, but were significantly different in shells from which cuticle had been removed. In conclusion, the IBV strains reduced the intensity of brown shell colour to different extents with a lower amount of PP IX in eggshells.

The impact of eggshell colour and spot area in Japanese quails: II. Slaughter and carcass characteristic

This study was carried out to investigate the effects of eggshell colour and spot properties (colour and size of the spot area) on growth performance and carcass traits of Japanese quail (Coturnix coturnix japonica) eggs. Study material were allocated to five groups according to their eggshell and spot colours: black spots on greyish white coloured eggshell (I), blue spots on greyish white coloured eggshell (II), diffuse brown spots on greyish brown coloured eggshell (III), brown spots on light green colored eggshell (IV), and small brown spots on greyish brown coloured eggshell (V). The size of the spotted area was determined in each egg group using digital image analysis. The groups did not differ for body weight and length of the shank at the end of the growth period. However, the groups differed significantly for carcass yield after slaughter (not eviscerated) and carcass yield. These parameters were highest in Group I (82.08 and 76.09%) and lowest in Group III (80.20 and 73.86%). Digital image analysis demonstrated that heart length, cardiac fat area, gizzard width, and intestine length varied between the groups. Cardiac fat area was largest in Group III (0.86 cm2) and smallest in Group V (0.65 cm2). Gizzard width was greatest in Group I (2.63 cm) and smallest in Group V (2.47 cm). Intestine length was greatest in Group V (78.45 cm) and smallest in Group IV (72.39 cm). Body weight, shank length, and slaughter and carcass weight do not vary in relation to eggshell colour or the size of the spotted area. The lengths of intestine and heart, gizzard width, and cardiac fat area do vary in relation to eggshell colour or the size of the spotted area.

EFFECT OF EGGSHELL COLOR ON THE EGG CHARACTERISTICS AND HATCHABILITY OF GUINEA FOWL (NUMIDA MELEAGRIS) EGGS

The objective of this study was to determine the effects of eggshell color of guinea fowl (Numida meleagris) eggs on eggshell quality and hatchery results. The highest mean grey value (MGV), integrated density (ID), lightness (L*) and Hue angle (H*) values were obtained in eggs with lighter eggshell color. The effects of color difference (DE*) value levels on egg characteristics were evaluated. Eggshell color presented different (p<0.01) MGV, ID, L*, redness (a*), yellowness (b*), H* and Chroma (C*) values. Eggs with lighter color presented thicker eggshells and lower egg weight loss on day 25 of incubation (p<0.05) compared with intermediate and darker eggs. Eggshell color did not have any significant effect on fertility and hatchability (p>0.05). In conclusion, under the conditions of the present study, eggshell color influenced eggshell thickness and weight loss, but not hatching parameters of guinea fowl eggs. Further studies on this subject should be carried out.

Oviposition time, flock age, and egg position in clutch in relation to brown eggshell color in laying hens

In Australia and other parts of the world, table eggs with uniform brown eggshell color are well regarded by consumers. Brown eggshell color has been positively correlated with certain egg characteristics such as shell strength and egg specific gravity, along with specific antibacterial functions. In the current study, the effect of hen oviposition time, flock age, and egg position in-clutch on the intensity of brown eggshell color was studied in commercial laying hens. The collected eggs were processed to measure egg weight, shell reflectivity, shell color (L*a*b*), quantification of protoporphyrin IX (PP IX), and shell thickness. Hen oviposition time had a statistically significant effect (P < 0.05) on egg weight, L*a*b*, amount of PP IX, and shell thickness. L* increased from 59.72 in the first half hour after lights on to 61.67 6 hours later, and PP IX per gram of eggshell decreased from 1.32×10(-7)mM to 1.26×10(-7)mM. Flock age had a significant effect on egg weight, L*a*b*, shell reflectivity, PP IX, and shell thickness. The mean egg weight increased from 55.4g at 25 wk of flock age to 63.3g at 75 wk of flock age. PP IX per gram of eggshell was 1.45×10(-7)mM at 25 wk and declined to 1.31×10(-7)mM at 75 wk of flock age. Individual hen clutch length was highly variable, ranging from 22 to 123 eggs in a single clutch. Egg position in a clutch had a significant effect on all egg quality variables measured; however, the R(2) values for each variable measured were low. The eggshell color declined to a greater extent with increasing position in a clutch for long clutches compared with short and medium clutches. In conclusion, hen oviposition time affected brown eggshell color with darker brown eggs laid early in the d and lighter colored brown eggs laid later in the morning. The intensity of brown color decreased with flock age, and egg position in-clutch had relatively little effect on brown eggshell color.

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

The aim of this research was to evaluate selection studies towards increasing eggshell colour intensity and homogeneity, without reducing egg production of brown-egg-laying hens at the Poultry Research Institute of Ankara, Turkey. This study was based on data obtained from 1342 pedigree Barred Rock-1 (BAR-1), 1158 pedigree Rhode Island Red-1 (RIR-1) and 611 hybrid (RIR-1xBAR-1 or ATAK-S) brown laying hens, where eggshell colour and egg production performances were determined. Hens were selected for dark, uniform shells and egg production performance, as paternal and maternal lines from RIR-1 and BAR-1 base populations. Colour coordinates; L* (brightness), a* (red/green scale), b* (yellow/blue scale) and eggshell colour index (SCI) were determined. The values of L*, b* and a* were significantly changed during the study. The estimated heritabilities for BAR-1 hens of egg weight (EW), L*, a*, b* and SCI were as follows: 0.62, 0.64, 0.62, 0.55 and 0.32; The RIR-1 hen values were as follows: 0.51, 0.74, 0.64, 0.22 and 0.39, respectively. It was concluded that the performance of parents and hybrids was better than that of the base populations, with respect to the characteristics studied.

Effect of tea polyphenols on production performance, egg quality, and hepatic antioxidant status of laying hens in vanadium-containing diets

This study was conducted to determine the effect of tea polyphenols (TP) on production performance, egg quality, and hepatic-antioxidant status of laying hens in vanadium-containing diets. A total of 300 Lohman laying hens (67 wk old) were used in a 1 plus 3 × 3 experiment design in which hens were given either a diet without vanadium and TP supplementation (control) or diets supplemented with 5, 10, or 15 mg V/kg and TP (0, 600, 1,000 mg/kg) diets for 8 wk, which included 2 phases: a 5-wk accumulation phase and a 3-wk depletion phase. During the accumulation phase, dietary vanadium addition decreased (linear, P < 0.01) albumen height and Haugh unit (HU), and TP supplementation mitigated (linear effect, P < 0.01) this reduction effect induced by vanadium. Eggshell thickness (linear, P < 0.01), redness (linear and quadratic, P < 0.05), and yellowness (linear and quadratic, P < 0.05) were decreased by vanadium and increased by the effect of TP when a vanadium-containing diet was fed. In the depletion phase, the bleaching effect on eggshells induced by vanadium disappeared one wk after vanadium withdrawal. Eggshell thickness, eggshell strength, albumen height, and HU were lower (P < 0.05) in the 15 mg/kg vanadium group compared with the control diet until 2 wk post vanadium challenge, but hens fed 15 mg/kg vanadium and 600 mg/kg TP showed no difference from the control diet only after 1 wk withdrawal. In the liver, the activity of glutathione S-transferases and glutathione peroxidase was increased (linear, P < 0.01) with the TP addition at 5 wk in the accumulation phase in the vanadium-containing diet; the malondialdehyde content increased (linear effect, P = 0.02) with the addition of vanadium. The results indicate that supplementation of 10 and 15 mg/kg vanadium resulted in reduced albumen quality, bleaching effect on eggshell color, and antioxidant stress in the liver. The effect of TP addition can prevent laying hens from the adverse effect of vanadium on egg quality, liver antioxidant stress and shorten the recovery time.

Haematocrit, eggshell colouration and sexual signaling in the European starling (Sturnus vulgaris).

BackgroundOne hypothesis to explain the blue–green colour of the eggs of many bird species is that it is a sexually-selected signal of the laying female’s quality, which males use to determine their investment. This hypothesis requires that eggshell pigmentation carries a cost or is otherwise linked to female quality. One potential cost is that biliverdin, a haem derivative and the pigment responsible for eggshell colouration, is limiting. To assess this potential cost, we attempted to manipulate haematocrit and haemoglobin in free-living European starlings (Sturnus vulgaris Linnaeus). Upon collecting unmanipulated first clutches, we treated females with phenylhydrazine (PHZ), a haemolytic agent, and measured the blue–green chroma and reproductive performance of replacement clutches. We also investigated whether eggshell colour was associated with haematocrit or haemoglobin levels in unmanipulated first clutches. To test whether eggshell colour might act as a sexual signal, we examined associations between eggshell colour and reproductive performance, as well as the provisioning rate of the male.ResultsPHZ-treatment did not affect eggshell colour in replacement clutches. In unmanipulated first clutches, eggshell colour was not correlated with haematocrit or haemoglobin levels. Eggshell colour was correlated with female mass in unmanipulated first clutches but not replacement clutches. Chicks from eggs with higher eggshell colour had higher haemoglobin levels and longer tarsi just prior to fledging, suggesting that eggshell colour could reflect brood quality. However, eggshell colour was not correlated with the provisioning rate of the male or any other measure of reproductive performance.ConclusionsWe found no evidence to support the hypothesis that the availability of resources required for the synthesis of pigment limits eggshell colour in European starlings, or that eggshell colour is used by males to determine their level of reproductive investment. We found little evidence that eggshell colour is correlated with female or offspring quality in this species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0084-x) contains supplementary material, which is available to authorized users.

Legacy Pollutants are Declining in Great Skuas (Stercorarius skua) but Remain Higher in Faroe Islands than in Scotland.

To monitor environmental pollutants in Faroese biota, samples from a top predator were analysed and put into a spatial and temporal context. Analysis of 20 Great Skua eggs sampled in 2012 from the Faroe Islands showed >70 % lower concentrations of legacy persistent organic pollutants (POPs) than in samples analysed in 1977. The 2012 Faroese eggs showed higher concentrations than for eggs in Shetland from about the same period (2008). Eggshells were analysed for sub-lethal effects but there were no detectable effects of legacy POP levels on eggshell colour or thickness. A temporal decline in legacy POPs would indicate a reduction in the general pollutant levels present in the environment as has been shown in other areas of the North Atlantic, but there are significant geographic differences in POPs levels likely due to differences in diet resulting in significantly different exposures on a relatively limited spatial scale.

Dynamic egg color mimicry.

Evolutionary hypotheses regarding the function of eggshell phenotypes, from solar protection through mimicry, have implicitly assumed that eggshell appearance remains static throughout the laying and incubation periods. However, recent research demonstrates that egg coloration changes over relatively short, biologically relevant timescales. Here, we provide the first evidence that such changes impact brood parasite–host eggshell color mimicry during the incubation stage. First, we use long‐term data to establish how rapidly the Acrocephalus arundinaceus Linnaeus (great reed warbler) responded to natural parasitic eggs laid by the Cuculus canorus Linnaeus (common cuckoo). Most hosts rejected parasitic eggs just prior to clutch completion, but the host response period extended well into incubation (~10 days after clutch completion). Using reflectance spectrometry and visual modeling, we demonstrate that eggshell coloration in the great reed warbler and its brood parasite, the common cuckoo, changes rapidly, and the extent of eggshell color mimicry shifts dynamically over the host response period. Specifically, 4 days after being laid, the host should notice achromatic color changes to both cuckoo and warbler eggs, while chromatic color changes would be noticeable after 8 days. Furthermore, we demonstrate that the perceived match between host and cuckoo eggshell color worsened over the incubation period. These findings have important implications for parasite–host coevolution dynamics, because host egg discrimination may be aided by disparate temporal color changes in host and parasite eggs.

Estimating the purebred-crossbred genetic correlation for uniformity of eggshell color in laying hens.

BackgroundUniformity of eggs is an important aspect for retailers because consumers prefer homogeneous products. One of these characteristics is the color of the eggshell, especially for brown eggs. Existence of a genetic component in environmental variance would enable selection for uniformity of eggshell color. Therefore, the objective of this study was to quantify the genetic variance in environmental variance of eggshell color in purebred and crossbred laying hens, to estimate the genetic correlation between environmental variance of eggshell color in purebred and crossbred laying hens and to estimate genetic correlations between environmental variance at different times of the laying period.MethodsWe analyzed 167,651 and 79,345 eggshell color records of purebred and crossbred laying hens, respectively. The purebred and crossbred laying hens originated mostly from the same sires. Since eggshell color records of crossbred laying hens were collected per cage, these records could be related only to cage and sire family. A double hierarchical generalized linear sire model was used to estimate the genetic variance of the mean of eggshell color and its environmental variance. Approximate standard errors for heritability and the genetic coefficient of variation for environmental variance were derived.ResultsThe genetic variance in environmental variance at the log scale was equal to 0.077 and 0.067, for purebred and crossbred laying hens, respectively. The genetic coefficient of variation for environmental variance was equal to 0.28 and 0.26, for purebred and crossbred laying hens, respectively. A genetic correlation of 0.70 was found between purebred and crossbred environmental variance of eggshell color, which indicates that there is some reranking of sires for environmental variance of eggshell color in purebred and crossbred laying hens. Genetic correlations between environmental variance of eggshell color in different laying periods were generally higher than 0.85, except between early laying and mid or late laying periods.ConclusionsOur results indicate that genetic selection can be efficient to improve uniformity of eggshell color in purebreds and crossbreds, ideally by applying combined crossbred and purebred selection. This methodology can be used to estimate genetic correlations between purebred and crossbred lines for uniformity of other traits and species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-016-0212-2) contains supplementary material, which is available to authorized users.

Synergistic effect of a combination of ultraviolet–C irradiation and sodium hypochlorite to reduce Listeria monocytogenes biofilms on stainless steel and eggshell surfaces

The present study demonstrates the synergistic effect of treatment with a combination of ultraviolet (UV)C (300, 600, 1200, and 1800 mWs/cm2) irradiation and sodium hypochlorite (NaOCl) (50, 100, 150, and 200 ppm) on Listeria monocytogenes ATCC 19113 biofilms formed on stainless steel and eggshell surfaces. The synergistic effect was not dependent on the dose of UV–C irradiation or the concentration of NaOCl. Synergistic reductions of biofilms after UV–C/NaOCl treatment on stainless steel and eggshells were 0.95–3.68 log CFU/cm2 and –0.22 to 1.02 log CFU/cm2, respectively. The largest synergistic reductions of biofilms were 3.68 log CFU/cm2 using 1800 mWs/cm2 UV–C and 200 ppm NaOCl on stainless steel, and 1.02 CFU/cm2 using 600 mWs/cm2 UV–C and 50 ppm NaOCl on eggshells. The Hunter colors of L*, a*, and b* were not significantly (P > 0.05) changed on eggshell surfaces treated with all single and combined treatments. The results in this study indicate that the combination treatment of 1800 mWs/cm2 UV–C/200 ppm NaOCl could be feasible for use on stainless steel surfaces in industrial kitchens, facilities, and restaurants. In addition, the combination of 600 mWs/cm2 UV–C/500 ppm NaOCl could possibly be used in egg production, processing, and distribution processes to enhance food safety without causing changes to the eggshell surface color.

The impact of eggshell colour and spot area in Japanese quails: I. eggshell temperature during incubation and hatching results

This study was carried out to investigate the effects of eggshell colour and spot properties (colour and size of the spot area) on eggshell incubation temperature and hatching outcomes of Japanese quail eggs (Coturnix coturnix japonica). Study material was allocated to five groups according to their eggshell and spot colours: black spots on greyish white coloured eggshell (I), blue spots on greyish white coloured eggshell (II), diffuse brown spots on greyish brown coloured eggshell (III), brown spots on light green coloured eggshell (IV), and small brown spots on greyish brown coloured eggshell (V). The size of the spotted area was determined in each egg group using digital image analysis. Mean relative weight losses of hatched and unhatched eggs between days 0-10 and 0-14 of embryonic development were 4.76% and 10.48% and 9.17% and 15.46%, respectively. The mean eggshell temperatures of hatched and unhatched eggs measured at the equatorial region on days 10 and 14 during embryonic development were 36.92 and 37.79 oC and 36.84 and 37.18 oC, respectively. Eggshell temperatures at the equatorial region on days 10 (36.89 oC) and 14 (37.57 oC) of embryonic development were lower than the fixed temperature of the incubator (37.6 oC). Fertility, hatchability of fertile eggs, and hatchability and embryonic mortality rates do not vary in relation to eggshell colour or the size of the spotted area.