Egg Components Research Articles

Digestible threonine:lysine ratios for light laying hens from 29 to 45 weeks

The objective was to determine the nutritional requirement of digestible threonine and the threonine: lysine ratios for light laying hens from 29 to 45 weeks of age. Two hundred Hy-Line-36® hens were distributed in a completely randomized design with five replicates and 10 birds per experimental unit and four treatments (5.50, 5.77, 6.05 and 6.30 g digestible threonine kg-1), establishing threonine: lysine of 69, 73, 76 and 80%. Four production cycles of 28 days each were evaluated: feed intake, feed conversion (kg dz-1), feed conversion (kg kg-1), egg laying percentage, weight and egg mass, percentage of egg components, internal egg quality and shell thickness. No effect of threonine levels was observed on egg production, weight and egg mass, internal egg quality, albumen and yolk percentage, specific gravity, shell thickness, feed intake, feed conversion (kg dz-1) and feed conversion ratio (kg kg-1). The ratio of digestible threonine: lysine to light laying hens in the period from 29 to 45 weeks is 69%, which corresponds to a daily consumption of 520 mg threonine bird-1 day-1.

Relación de valina y lisina en las dietas de codornices japonesas

To determine the relationship valine to lysine for Japanese quails during the period of production, it was conducted an experiment in DZO-UFV using 480 subspecies Japanese quails (Coturnix coturnix japonica) with, 284 days of age. The birds were distributed in a completely randomized desing with six treatments (relationships of valine to lysine), ten replicates and eight birds per experimental unit. The treatments consisted of a basal diet deficient in valine with 18.6% crude protein and 2900 kcal metabolizable energy/kg, supplemented with five levels of L-Valine (0.051, 0.101, 0.151, 0.202 and 0.252%) corresponding to the relationships of valine to lysine of 0.75; 0.80, 0.85, 0.90, 0.95 and 1.00% respectively, and the lysine set at 1.00%. The variables studied were: feed intake (g/bird/day), egg production per bird day (%), production of commercial eggs (%), egg weight (g), egg mass (g/bird/day), feed conversion by egg mass (kg feed/kg egg), feed per dozen eggs (kg feed/dz of eggs), weight of components (yolk, albumen and shell), percentage of eggs components and specific gravity (g/cm³). There was no significant effect in the parameters evaluated in terms of relations of valine to lysine studied. The relationship of valine to lysine in the ration of 0.75 provides satisfactory performance and eggs quality of Japanese quail.

Reproductive performance of breeder quails fed diets supplemented with L-cysteine-coated iron oxide nanoparticles.

The objective of this study was to investigate the effects of L-cysteine-coated iron oxide nanoparticles on reproductive performance in breeder quails. The five treatment diets consisted of (i) negative control diet not supplemented with iron, (ii) positive control diet supplemented with 60mg/kg of Fe3 O4 and (iii) experimental diets supplemented with 0.6, 6 and 60mg/kg of L-cysteine-coated iron oxide nanoparticles. A total of 100 seven-day-old quail chicks were weighed and randomly placed to five groups of five replicate cages. Four quails (one male and three females) were raised in each cage (50×15×17cm). Egg production, feed consumption and egg weight were recorded daily and calculated on a hen per day basis. Egg components, fertility, hatchability and day-old chicks hatched from their eggs were measured at the end of the experiment. The percentage of egg production and egg mass of the 6mg/kg Fe3 O4 -Cys NPs group were significantly higher than those of the control groups. Throughout the experimental period, the highest weekly egg weight was recorded for the 60mg/kg Fe3 O4 -Cys NPs group. Fertility was improved by diet supplemented with iron, both FeSO4 and Fe3 O4 -Cys NPs. The breeder fed Fe3 O4 -Cys NPs had the highest day-old chicks weight. The results of this study showed that Fe3 O4 nanoparticles that were coated by L-cysteine could improve availability and utilization of iron in diet. Finally, it was proposed that Fe3 O4 -Cys NPs could be used as feed additives in quails.

Níveis de sódio na ração de poedeiras semipesadas após o pico de postura criadas em clima quente

The objective of this study was to estimate the sodium (Na) requirements of semi-heavy laying hens reared in a hot climate after peak lay. A total of 120 Hisex Brown hens, 48 weeks of age, were used. The birds were allocated in a completely randomized design consisting of five treatments, six replicates and four animals per experimental unit. The experimental diets were formulated with corn and soybean meal and the treatments consisted of five levels of sodium (0.12, 0.17, 0.22, 0.27 and 0.32%) derived from common salt. The following parameters were evaluated: feed intake (g), egg production (%), egg weight (g), egg mass (g), feed conversion (kg) per kilogram of eggs and per dozen eggs, specific gravity (g/cm 3 ), shell thickness (mm), egg components including egg yolk (g and %), albumin (g and %) and shell (g and %), viability (%), and variation in body weight (g) of the birds. There was no effect (P>0.05) of sodium levels on egg yolk weight (g) or albumin percentage. A decreasing linear effect (P<0.01) was observed for feed intake, which decreased with increasing sodium level in the diet. A quadratic effect (P<0.05) was found for egg production, egg weight, feed conversion per kilogram of eggs and dozen eggs, albumin and shell weight, specific gravity, shell thickness, and percentage of shell and egg yolk. A sodium level higher than 0.27% negatively influenced egg components and zootechnical performance of the birds. The inclusion of 0.20% sodium in the diet after peak lay is recommended for semi-heavy laying hens reared in a hot climate to increase egg quality and productive performance.

Uticaj sistema gajenja, genotipa i starosti kokoši nosilja na masu jaja i udeo glavnih delova jaja

The aim of this study was to evaluate the effect of rearing system, genotype and hens age on egg weight and eggs components share. The tested rearing systems were the floor and organic, and tested genotypes were Isa Brown hybrid and New Hampshire breed. Eggs were collected for analyses three times in production cycle (32 weeks hens age, 48 weeks hens age, and 72 weeks hens age). In these samples (fifteen eggs per group, eggs were one day old) were investigated: egg weight, albumen share, yolk share and shell share. Egg weight was increased with hens age. Also, the interaction between the genotype and hens age was found, so the New Hampshire eggs in 32 weeks had less weight then Isa Brown eggs (p≤0.05), while in the 48 and 72 weeks this difference was lost (p≥0.05). The share of egg albumen and yolk was significantly affected by the rearing system, genotype and hens age (p≤0.05). Floor produced eggs had a lower proportion of albumen and a higher proportion of yolk compared to organic eggs. New Hampshire eggs had a higher content of yolk and the smaller content of albumen compared to Isa Brown eggs (p≤0.05). With hens age, the share of yolk was increased and albumen share was decreased. Interaction of all three studied factors - rearing system x genotype x hens age had the most important effect on the shell share.

Assessment of a probiotic Containing Bacillus Subtilis on the Performance and Gut Health of Laying Japanese Quails (Coturnix Coturnix Japonica)

ABSTRACT The present study was carried out to determine the effects of the inclusion of a spore-forming probiotic (Bacillus subtilis) in laying Japanese quail diets as an alternative to growth-promoting antibiotics to help produce healthy eggs and meat. This experiment was conducted as a completely randomized design with three treatments (control, 0.05% bacitracin methylene disalicylate (BMD), or 0.1% Bacillus subtilis) of five replicates of 11 quails each. Feed intake and egg production were recorded daily on cage basis. Body weight was determined at the beginning and end of the trial (36 and 42 weeks). At the end of the experiment (42 weeks), antibodies against Newcastle disease and avian influenza, egg components, Haugh units, eggshell quality and breaking strength, blood parameters, cecal microbial population, villus length, and crypt depth were measured. The dietary inclusion of Bacillus subtilis and BMD significantly (p≤0.05) increased egg production and egg weight; however, eggshell thickness and breaking strength, Haugh units, and eggshell percentages were not affected. The dietary addition of both products significantly (p≤0.05) decreased plasma cholesterol levels and increased LDL levels, as well as antibody levels against Newcastle disease and avian influenza (p≤0.01). In birds fed Bacillus subtilis and BMD, crypt depth was reduced, but villus height and villus to crypt ratio were significantly increased (p≤0.001) compared with those fed the basal diet. Cecal coliforms, E. coli, and Salmonella counts were reduced (p≤0.01) in quails fed the diets containing Bacillus subtilis and BMD compared those quails fed the non-supplemented diet. The results of this study demonstrated that in absence of AGPs, the inclusion of a spore-forming probiotic partially improves the performance of laying quails.

Supplemental defatted microalgae affects egg and tissue fatty acid composition differently in laying hens fed diets containing corn and flaxseed oil

Effects of defatted microalgae (DFA) on fatty acid composition of eggs and tissues of hens have not been well studied. This experiment was to determine how low concentrations of supplemental DFA in the presence or absence of flaxseed oil (FO) altered fatty acid profiles of egg yolk, liver, adipose tissue, and plasma of layers. A total of 60 Shaver Leghorn layer hens (individually caged, 20-wk old) were allotted into 6 groups (n = 10) and fed a corn/soybean meal basal diet containing 0, 3, or 5% DFA and 0 (1.5% corn oil, CO) or 1.5% FO for 6 wk. BW, ADFI, egg production rate, and egg component weights were not affected by any of the dietary treatments at various time points, but egg yolk color was changed (P < 0.05) with increasing concentrations of DFA. The concentration of n-3 fatty acids in egg yolk and plasma were elevated by FO up to 9-fold (P < 0.05) starting at wk 1 or 2, and 39 to 83% (P < 0.05) by DFA. Supplemental DFA improved (P < 0.05) n-6/n-3 fatty acid ratios in egg yolk and plasma from 13 to 23 and 7 to 13, respectively, only in hens fed diets without FO. Fatty acid profiles of liver and adipose tissue (at wk 6) displayed responses to supplemental DFA and FO similar to those of egg yolk or plasma. In conclusion, supplemental 3 or 5% DFA caused moderate enrichments of n-3 fatty acids and decreased the n6/n3 fatty acid ratios of egg yolk and tissues in hens fed diets without FO.

Effect of dietary digestible lysine concentration on performance, egg quality, and blood metabolites in laying hens

An experiment was conducted to evaluate the effect of dietary digestible lysine concentration on productive performance, egg quality, and blood metabolites in laying hens. A completely randomized block design was performed with 5 treatments and 6 replicates of 8 Hy-line W-36 hens each, from 32 to 44 wk of age. The treatments were 5 digestible lysine concentrations (0.657, 0.707, 0.757, 0.807, and 0.857% of diet). Feed intake was significantly increased with each increment in dietary digestible lysine concentration. Significant improvement in egg production, egg weight, egg mass, Haugh unit, and FCR were observed by an increase in lysine intake. Dietary lysine concentration did not have a significant impact on percentage of egg components, specific gravity, eggshell thickness, DM, and protein constituents of eggs. Dietary digestible lysine concentration did not have a significant effect on triglyceride, cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), uric acid, and total protein in plasma. The digestible lysine requirements for optimal egg production, egg mass, and egg weight (32 to 44 wk of age), based on the linear broken-line regression analysis, were 814, 810 and 778 (mg/b/d), respectively. Whereas, these values were 4, 3.9, and 6 percent less than those estimated by the quadratic broken-line model, respectively.

Egg sensitization, allergy and component patterns in African children with atopic dermatitis

Egg allergy is the most common food allergy in children with atopic dermatitis (AD). This study aimed to determine the prevalence of egg allergy, component patterns and predictive values of screening tests in egg allergy in South African children with AD. This was a prospective, observational study in a paediatric university hospital in Cape Town. Children with AD, aged 6 months to 10 years, were recruited randomly. They were assessed for sensitization and allergy to egg by questionnaire, skin prick tests (SPT), Immuno Solid Phase Allergen Chip (ISAC 103® ) test, ImmunoCAP component tests to egg and ovomucoid (Gal d 1) and incremental food challenges. Hundred participants (59 Black Africans and 41 of mixed ethnicity) were enrolled, median age 42 months. There was a high rate of egg sensitization of 54% and prevalence of confirmed egg allergy of 25%. History and screening laboratory tests overestimated egg allergy significantly. SPT to fresh egg white was significantly more sensitive in diagnosing egg allergy than SPT to the commercial egg white extract and produced the highest area under the receiver operator characteristics curve of all the screening tests in predicting true egg allergy. In those participants sensitized to egg, the component ovomucoid was best at differentiating true egg allergy from tolerance. Commonly used 95% positive predictive values (PPVs) for SPT to egg and ImmunoCAP egg white produced low PPV of 57% and 74%, respectively, in this population overall, with generally poorer predictive values amongst the Black Africans than the mixed ethnicity participants. A SPT to fresh egg of 17 mm and ImmunoCAP egg white of 13 kU/l produced the best PPV for egg allergy in this population. The prevalence of egg allergy is high in African children with AD, but history of egg allergy and sensitization to egg significantly overestimate the true egg allergy rate. SPT to fresh egg white was more sensitive than that to commercial egg white extract; hence, fresh egg white should be recommended in an egg allergy screening panel. The component ovomucoid was useful for differentiating allergy from tolerance in egg-sensitized participants. Population-specific 95% PPV for egg allergy tests may need to be established in developing world populations.

Relationship between specific IgE to egg components and natural history of egg allergy in Danish children.

The majority of egg-allergic children develop tolerance over time. However, it may take numerous of consecutive egg challenges to get there as no good indices to predict tolerance exist. To investigate whether serial measurements of specific IgE to egg white, ovomucoid, ovalbumin, conalbumin, lysozyme, and egg yolk could improve the specificity of the diagnostic workup and aid in the decision when to rechallenge egg-allergic children. The outcome of oral food challenges with hen's egg and corresponding specific IgE levels were evaluated in children referred to The Allergy Center within an 8-year period. The egg-allergic children were rechallenged and had specific IgE levels measured once a year. During a median follow-up of 26 months, 287 challenges and corresponding 287 serum analyses were performed in 130 children. Of the 130 children, 99 were egg allergic and 82 of these were rechallenged. Based on the initial diagnostic challenges only, area under the curve (AUC) estimates of the ability of specific IgE titers to distinguish between egg sensitization and egg allergy were only modest (maximum 0.83) and provided no clinical meaningful decision points. Specific IgE levels at baseline did not differ between tolerant and persistent allergic children. However longitudinally, acquisition of tolerance was associated with a decrease in IgE to egg white and to ovomucoid. In all cases of an increase in IgE to ovomucoid, the rechallenge was positive. The decision when to rechallenge egg-allergic children should encounter the course of specific IgE.

Bovine meat and Bone Meal as an Economically Viable Alternative in Quail Feeding in the Final Phase

Bovine meat and bone meal (MBM) has been used as a low-cost protein source in corn- and soybean meal-based poultry diets. However, to date, no studies investigating the effect of the dietary inclusion of MBM on the performance of Japanese quails and on egg production costs were found in literature. In this study, 600 Japanese quails in lay were distributed in a completely randomized experimental design consisting of six treatments (replacement levels of soybean meal by MBM:0, 1, 2, 3, 4, and 5%) with five replicates of 20 birds each to investigate if MBM is a viable alternative to maintain or to improve the live and economic performances of these birds. Treatments consisted of a control diet, based on corn and soybean meal, with no inclusion of MBM, and diets formulated with increasing levels (1, 2, 3, 4, and 5%) of MBM inclusion at the expense of soybean meal. The studied parameters were evaluated in four periods of 28 days each. Live performance parameters (egg weight, g; average egg production, %; egg weight, g; feed intake, g; feed conversion ratio per egg mass, kg/kg and per dozen eggs, dz/kg; and livability, %); egg quality parameters (proportion of egg components, yolk, albumen, eggshell %; egg specific weight, g/cm3); and economic parameter (bio-economic nutritional index) were determined. Only egg weight, egg specific weight, and eggshell percentage were affected (p<0.05) by the treatments. Our results show that inclusion of bovine meat and bone meal can be added to the diet of Japanese quails in lay, causing no performance losses and promoting feed cost savings up to 5.24%.

Heritable variation in maternally derived yolk androgens, thyroid hormones and immune factors.

Maternal reproductive investment can critically influence offspring phenotype, and thus these maternal effects are expected to be under strong natural selection. Knowledge on the extent of heritable variation in the physiological mechanisms underlying maternal effects is however limited. In birds, resource allocation to eggs is a key mechanism for mothers to affect their offspring and different components of the egg may or may not be independently adjusted. We studied the heritability of egg components and their genetic and phenotypic covariation in great tits (Parus major), using captive-bred full siblings of wild origin. Egg mass, testosterone (T) and androstenedione (A4) hormone concentrations showed moderate heritability, in agreement with earlier findings. Interestingly, yolk triiodothyronine hormone (T3), but not its precursor, thyroxine hormone (T4), concentration was heritable. An immune factor, albumen lysozyme, showed moderate heritability, but yolk immunoglobulins (IgY) did not. The genetic correlation estimates were moderate but statistically nonsignificant; a trend for a positive genetic correlation was found between A4 and egg mass, T and lysozyme and IgY and lysozyme, respectively. Interestingly, phenotypic correlations were found only between A4 and T, and T4 and T3, respectively. Given that these egg components are associated with fitness-related traits in the offspring (and mother), and that we show that some components are heritable, it opens the possibility that natural selection may shape the rate and direction of phenotypic change via egg composition.

Implementation of an Enzyme Linked Immunosorbent Assay for the Quantification of Allergenic Egg Residues in Red Wines Using Commercially Available Antibodies

Since the early 2000s, labeling of potentially allergenic food components to protect people who suffer from food allergies is compulsory in numerous industrialized countries. In Europe, milk and egg components used during the winemaking process must be indicated on the label since July 1, 2012. Several ELISA procedures have been developed to detect allergenic residues in wines. However, the complexity of the wine matrix can inhibit the immunoenzymatic reaction. The aim of this study was to implement an ELISA assay for the detection of ovalbumin in red wines using commercially available antibodies. The specificity of the acquired antibodies and the absence of cross reactivity were assessed by immunoblotting and ELISA. An ELISA assay with a LOD of 14.2 μg/L and a LOQ of 56.4 μg/L of ovalbumin in aqueous solution was obtained. Differences in ELISA signals were observed when analyzing various fining agents, although reproducible conformation of the antigen could be reached for the comparison of ovalbumin and Ovicolle. The differences between samples in terms of pH could be leveled but the inhibition of the ELISA signal, positively correlated to the tannin content of the wines, could not be suppressed. Thus, standard curves of ovalbumin in several wines were obtained by relative quantification. The control steps and the difficulties encountered presented in this study should be considered by anybody working toward the development of ELISA assays for the detection of allergenic residues in complex food matrices.

Digestible tryptophan-to-digestible lysine ratio in diets for laying hens of 42 to 58 weeks of age

SUMMARY To determine the ideal digestible tryptophan-to-digestible lysine ratio in diets for laying hens of 42 to 58 weeks of age, 240 Hy-Line W-36 hens at 42 weeks of age were distributed in a completely randomized design with five treatments, eight replicates and six birds per experimental unit. At 42 weeks of age, the birds were subjected to experimental treatments that consisted of diets with equal amounts of nutrients, except for the digestible tryptophan level. The digestible tryptophan levels in the experimental diets were 0.149, 0.160, 0.171, 0.182 and 0.193%, generating digestible tryptophan-to-digestible lysine ratios of 21.5, 23.1, 24.6, 26.2 and 27.8%. The digestible lysine level in the diets was sub-optimal (0.694%). The same ratios between lysine and the other amino acids were maintained in all experimental diets. The ideal digestible tryptophan-to-digestible lysine ratio was estimated through the studied parameters using analysis of variance and polynomial regression analysis (α = 0.05). The digestible tryptophan-to-digestible lysine ratio in diets quadratically affected egg production, egg mass, feed conversion per egg mass and use efficiency of digestible lysine for egg mass. However, there were no effect (P&gt;0.05) on egg weight, feed conversion per dozen eggs, use efficiency of digestible lysine for number of eggs produced, percentage of egg components and weight gain. The digestible tryptophan-to-digestible lysine ratio estimated for theses parameters ranged from 23.6 to 24.3%. The digestible tryptophan-to-digestible lysine ratio recommended in diets for laying hens of 42 to 58 weeks of age is 24.3%.

Effect of digestible methionine + cystine concentration on performance, egg quality and blood metabolites in laying hens

The estimation of sulphur amino acid requirement is a vital key to providing appropriate nutrition in poultry. The estimation of amino acid requirement depends on what production parameter is taken into consideration for optimisation.A complete randomised block design was performed with 5 treatments and 6 replicates of 8 Hy-line layers (W-36) each from 32 to 44 weeks of age. The blocks were made to have a replicate of each treatment. The dietary treatments were consisted of 5 concentrations of digestible sulphur amino acid (DSAA) at 5.1, 5.6, 6.1, 6.6 and 7.1 (g/kg).Egg production, egg mass, egg weight and feed conversion ratio (FCR) were significantly affected by an increase in DSAA intake. However, feed intake, egg component yield, Haugh unit, specific gravity, eggshell thickness, egg protein and dry matter (DM) were not altered by DSAA intake.A significant increment in plasma high-density lipoprotein was concomitant with a reduction in low-density lipoprotein when DSAA intake was increased. However, triglyceride, cholesterol, uric acid and total protein in plasma were not affected by DSAA intake.The DSAA requirements estimated by the linear broken-line model to optimise egg production, egg mass, egg weight and FCR were 678, 673, 641 and 656 mg/bird.d in the whole experimental period, respectively.The DSAA requirement estimated by the quadratic broken-line model to optimise egg production, egg mass, egg weight and FCR were 4.71%, 7.87%, 8.73% and 7.62% higher than those estimated by linear broken-line fit model in the whole experimental period, respectively.

Coupling non invasive and fast sampling of proteins from work of art surfaces to surface plasmon resonance biosensing: Differential and simultaneous detection of egg components for cultural heritage diagnosis and conservation

Despite the wide application of surface plasmon resonance (SPR) to a broad area of interests, from environment to food analysis, from drug discovery to diagnostics, its exploitation in cultural heritage conservation is still unexplored. Water-based highly viscous polymeric dispersions (HVPD) composed by partially hydrolyzed polyvinyl acetate (PVA), borax, and water, were recently developed and successfully applied for the selective removal of surface degradation patinas (i.e. protein materials, natural resins etc.) from paintings of historical and artistic interest. This approach is here coupled for the first time to a SPR biosensor to simultaneously recognize albumen, yolk, or their mixtures in HVPD extracts. Ovalbumin and immunoglobulin Y are selected as analytes for egg white and yolk recognition, respectively. The biosensor was first characterized on standard analytes within the range 0–400mgL−1 and then on fresh and dried egg albumen and yolk down to 2·10^4 and 1·10^5 dilution factors, respectively. Once optimized, the biosensor was combined to the HVPD application on simulated and real art samples for the evaluation of hen egg presence in the extract, i.e. albumen, yolk, or their co-presence in the matrix. For a contemporary ‘sacred icon’, realized by the traditional egg tempera procedure described by Cennino Cennini, the biosensor successfully distinguished different uses of egg components for the realization of painted and gilded areas, i.e. yolk and albumen, respectively. Finally, a XVIII century italian painting whose the realization technique is unknown, was tested confirming its egg tempera-based realization technique.

EFFECTS OF DIFFERENT SUPPLEMENTS INCLUSION OF THE ENRICHED DIET ON PRODUCTIVE PERFORMANCE AND EGG STRUCTURE

Nutritional manipulation and genetic selection for egg size and production may lead to changes in egg components. This experiment was carried out to analyze the egg structure parameters of eggs produced by Hisex Brown laying hens fed with diet with different supplements inclusion. The intensity of egg production was significantly higher in the groups fed with enriched feed with iodine (90.00%), vitamin E (90.00%) and selenium (91.98%), and significantly lower in the group fed with DHA inclusion feed (76.00%) in respect to the control group (82.00%), confidence interval of 95%. Concerning diet supplemented with selenium and diet supplemented with vitamin E, the egg yolk weight was statistically different compared with the control group (confidence interval of 95%). The yolk weight averaged 1.80 g and 1.29 g more than yolk weight in the control eggs, respectively. The egg shell weight was statistically different in diet enriched with iodine compared with the control. The egg shell weight averaged 1.48 g less per egg for the eggs enriched with iodine with 17.45% less underweight than the control eggs. Enriched eggs offer consumer a variety of value-added options for their egg purchase. Although enriched eggs may provide consumers with a specific quality attribute or healthful ingredient, they do not appear to provide quality and value in a traditional sense as defined by the standards of quality and grade.

In search of genetic constraints limiting the evolution of egg size: direct and correlated responses to artificial selection on a prenatal maternal effector.

Maternal effects are an important force in nature, but the evolutionary dynamics of the traits that cause them are not well understood. Egg size is known to be a key mediator of prenatal maternal effects with an established genetic basis. In contrast to theoretical expectations for fitness-related traits, there is a large amount of additive genetic variation in egg size observed in natural populations. One possible mechanism for the maintenance of this variation is through genetic constraints caused by a shared genetic basis among traits. Here we created replicated, divergent selection lines for maternal egg investment in Japanese quail (Coturnix japonica) to quantify the role of genetic constraints in the evolution of egg size. We found that egg size responds rapidly to selection, accompanied by a strong response in all egg components. Initially, we observed a correlated response in body size, but this response declined over time, showing that egg size and body size can evolve independently. Furthermore, no correlated response in fecundity (measured as the proportion of days on which a female laid an egg) was observed. However, the response to selection was asymmetrical, with egg size plateauing after one generation of selection in the high but not the low investment lines. We attribute this pattern to the presence of genetic asymmetries, caused by directional dominance or unequal allele frequencies. Such asymmetries may contribute to the evolutionary stasis in egg size observed in natural populations, despite a positive association between egg size and fitness.

How important is the eggshell as a source for initial acquisition of Salmonella in hatchling turtles?

How and when turtles first acquire gut microflora is largely speculative. In this study, the eggshell and hatching process were evaluated for their role in the initial acquisition of Salmonella, by red-eared slider turtles (Trachemys scripta elegans). First, we examined whether the eggshell is a viable substrate for bacterial persistence during incubation, and if internal egg components (i.e., albumen, yolk, and embryo) have detectable bacterial loads. Second, we experimentally manipulated Salmonella by treating eggs with combinations of Salmonella and gentamicin, an effective Gram-negative antibiotic. We found that the eggshell is a viable substrate for maintaining bacteria, as well as an effective barrier to Salmonella transmission as internal egg components were largely bacteria-free. Water samples collected 18 days post-hatch from individuals that were experimentally inoculated with a topical application of Salmonella as eggs had a higher prevalence of Salmonella than those from eggs inoculated with Salmonella but topically treated with gentamicin prior to hatching, control eggs, and eggs only treated with gentamicin, but by day 35 post-hatch there were no detectable differences among the treatment groups. Though it can also act as a barrier that prevents the bacteria from infecting the embryo prior to hatching these findings suggest that the eggshell is a likely source of Salmonella infection in turtle hatchlings.

Vaccination of chickens decreased Newcastle disease virus contamination in eggs

Newcastle disease is an important health issue of poultry causing major economic losses and inhibits trade worldwide. Vaccination is used as a control measure, but it is unknown whether vaccination will prevent virus contamination of eggs. In this study, hens were sham-vaccinated or received one or two doses of inactivated LaSota vaccine, followed three weeks later by virulent Newcastle disease virus (NDV) challenge. Eggs were collected daily and shell, albumen and yolk were subjected to virus isolation, as were oral and cloacal swabs at 2 and 4 days post-challenge (dpc). A second experiment evaluated the distribution of the virus in the reproductive tract of non-vaccinates. All vaccinated chickens survived challenge, and the levels of virus shed from cloacal swabs were decreased significantly when compared to shams. In non-vaccinated hens, virus was detected in the ovary and all segments of the oviduct. Yolk, albumen and eggshell surface from eggs laid at day 4 and 5 post-infection by sham-vaccinated hens were positive for NDV, but eggs from LaSota vaccinated hens lacked virus in internal egg components (i.e. yolk and albumen) and had reduction in the number of positive eggshell surfaces. These results indicate virulent NDV can replicate in the reproductive tract of hens and contaminate internal components of eggs and eggshell surface, but vaccination was able to prevent internal egg contamination, reducing eggshell surface contamination, and reducing shedding from digestive and respiratory tracts in virulent NDV challenged hens.