Embryonic growth and antioxidant provision in avian eggs

In ovo injection of soy isoflavones on hatching performance and intestinal development of newly hatched chicks

This study aimed to evaluate the effects of in ovo injection of soy isoflavones (ISF) on hatchability, body weight, antioxidant status and intestinal development of newly hatched broiler chicks. One hundred and eighty fertile eggs were divided as follows: the control group, 3 mg/egg ISF (low dose) and 6 mg/egg ISF (high dose) on the 18th day of incubation. The results demonstrated that in ovo inclusion of 6 mg of ISF significantly increased hatchability and hatch weight. Both doses of ISF inclusion elevated the serum glutathione peroxidase and slightly decreased malondialdehyde compared to the control group. The high dose of ISF brings higher villus height and a higher villus/crypt ratio in chicks. Moreover, the mRNA levels of tumour necrosis factor- α and interferon-gamma in the spleen were significantly decreased. The ISF treatments showed an improvement in intestinal enzyme expression levels of sucrose isomaltase and mucin 2  as well as tight junction protein (TJ) mRNA expression of claudin-1 at high doses of ISF (p < 0.05) when compared with the other groups. Furthermore, the mRNA level of IGF-1 was increased in the high doses of ISF compared to the control. Overall, these findings indicate that in ovo administration of ISF on the 18th day of incubation enhances hatchability, antioxidant status and intestinal morphometrics in hatched chicks and modulates the expression of proinflammatory cytokines, TJs and insulin-like growth factor. In addition, the sustainability of antioxidants and other positive effects of ISF may increase chick viability and growth performance.

Effect of In Ovo Administration of a Multi-Strain Probiotic and Zinc Glycine Chelate on Antioxidant Capacity and Selected Immune Parameters in Newly Hatched Chicks

The aim of this study was to determine the effect of in ovo co-supplementation of chicken embryos with a multi-strain probiotic containing effective microorganisms and zinc glycine chelate on total antioxidant capacity; concentrations of sulfhydryl groups, bityrosine bridges, formylkynurenines, hydroperoxides, proteins, corticosterone, pro- and anti-inflammatory cytokines and heat shock proteins; and the activity of catalase and superoxide dismutase in the serum, yolk sac and tissues of broiler chickens at 12 h and at 7 days after hatching. The results indicate high SOD activity in the small and large intestines of chicks at 12 h post-hatch in the groups receiving the multi-strain probiotic and in the small intestine and yolk sac of birds receiving the multi-strain probiotic and Zn-Gly chelate. High concentrations of TNF-α and IFN-γ in the yolk sac and serum after in ovo administration of Zn-Gly chelate were observed 12 h after hatching. The use of a probiotic and a probiotic with Zn-Gly chelate increased the total antioxidant capacity in the tissues of chickens. It can be concluded that in ovo administration of a multi-strain probiotic and Zn-Gly chelate can maintain the oxidant/antioxidant balance in chickens and increase the defense capacity against oxidative stress.

Calcium anacardate and its association with citric acid in diets for meat-type breeding quails

The purpose of this study was to evaluate the effects of using calcium anacardate (CaA) as a source of anacardic acid and its association with citric acid (CA) in diets for breeding quails on the performance, the egg quality, incubation parameters, and progeny performance. Were used 540 quails European quails (Coturnix coturnix coturnix) that were 21 weeks old, housed in laying cages based on a completely randomized design, with nine treatments and six replications of 10 quails per parcel, with each experimental unit having eight females and two males. The following additions to the diet were evaluated: 1, no addition (control diet); 2, 0.25% CaA; 3, 0.25% CaA and 0.25% CA; 4, 0.50% CaA; 5, 0.50% CaA and 0.25% CA; 6, 0.50% CaA and 0.50% CA; 7, 0.75% CaA; 8, 0.75% CaA and 0.25% CA; and 9, 0.75% CaA and 0.50% CA. The treatments had no significant effects on the performance of the breeding quails, incubation parameters, and progeny performance. For egg quality, there was only an effect on yolk lipid oxidation, which was lower for eggs from quails fed the diets containing 0.50% CaA and 0.25% CA, 0.50% CaA and 0.50% CA, or 0.75% CaA alone, when compared with the control group. Considering that including CaA with or without CA in diets for breeding quails only affected yolk lipid oxidation, it can be recommend including 0.50% CaA and 0.25% CA or 0.75% CaA alone to mitigate oxidative damage in the yolk of fertile eggs.

Effect of Hydrogen Oxide-Induced Oxidative Stress on Bone Formation in the Early Embryonic Development Stage of Chicken

The current study aimed to monitor the impact of H₂O₂-induced oxidative stress on avian bone formation during the early stage of embryonic development. Fertilized Cobb broiler eggs were divided into five treatment groups and micro-injected with varying concentrations of H₂O₂, i.e., control (PBS; 0 nM), 10 nM, 30 nM, 100 nM, and 300 nM, on embryonic day 3, with continued incubation thereafter. The treatment concentrations were selected based on the level of lipid peroxidation and the survival rate of embryo. Embryos were collected at 6 h, 24 h, 48 h, and 72 h post-injection. The mRNA expression levels of apoptotic markers, antioxidant enzymes, and early bone formation gene markers were measured. The results showed that the microinjection of H₂O₂ altered the expression pattern of antioxidant enzymes' mRNA during early embryogenesis and decreased the expression of COL1A2 and COL2A1 at 6 h and 24 h post-injection. Decreased expression of BMP, BGLAP, and RUNX2 was observed 48 h post-injection. Additionally, a shorter embryo length was observed in the 100 nM and 300 nM H₂O₂ treatment groups 72 h post-injection. In conclusion, H₂O₂-induced oxidative stress suppressed the expression of bone formation gene markers, with chronic effects on avian embryonic development.

Hepatic Gene Expression Profiling of American Kestrels (Falco sparverius) Exposed In Ovo to Three Alternative Brominated Flame Retardants

A number of brominated flame retardants (BFRs) have been reported to interfere with the thyroid signaling pathway and cause oxidative stress in birds, yet the underlying shifts in gene expression associated with these effects remain poorly understood. In this study, we measured hepatic transcriptional responses of 31 genes in American kestrel (Falco sparverius) hatchlings following in ovo exposure to one of three high-volume alternative BFRs: 1,2-bis(2,4,6-tribromophenoxy) ethane (BTPBE), bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), or 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB). Hatchling kestrels exhibited shifts in the expression of genes related to oxidative stress (CYP, GSTA, SOD, and GPX1), thyroid hormone metabolism and transport (DIO1, DIO2, and TTR), lipid and protein metabolism (PPAR, HMGCR, FAB1, and LPL), and cytokine-mediated inflammation (TLR3, IL18, IRF7, STAT3, RACK1, and CEBPB). Male and female hatchlings differed in which genes were differentially expressed, as well as the direction of the effect (up- vs. downregulation). These results build upon our previous findings of increased oxidative stress and disrupted thyroid signaling pathway in the same hatchlings. Furthermore, our results indicate that inflammatory responses appear to occur in female hatchlings exposed to BTBPE and EHTBB in ovo. Gene expression analysis revealed multiple affected pathways, adding to the growing evidence that sublethal physiological effects are complex and are a concern for birds exposed to BTBPE, EHTBB, or TBPH in ovo.

Thyroid disruption and oxidative stress in American kestrels following embryonic exposure to the alternative flame retardants, EHTBB and TBPH

Brominated flame retardant chemicals, such as 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB) (CAS #: 183658-27-7) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) (CAS #: 26040-51-7), have been detected in avian tissues and eggs from remote regions. Exposure to EHTBB and TBPH has been shown to cause oxidative stress and altered thyroid function in rodents and fish, yet no controlled studies have examined potential adverse effects of exposure in birds. Because flame retardants have been detected in wild raptors, we used American kestrels (Falco sparverius) as a model raptor to determine whether in ovo exposure to EHTBB or TBPH affected growth, hatching success, oxidative stress, or thyroid function. We exposed kestrel embryos to nominal concentrations (10, 50, or 100 ng g^-1 egg weight) of EHTBB and TBPH via egg-injection on embryonic day 5. Embryonic exposure (~23 d) to EHTBB increased thyroid gland mass, reduced glandular colloid and total thyroxine (T4) in hatchling males and females, whereas deiodinase enzyme activity increased in males but decreased in females. Hatchlings exposed to TBPH in ovo exhibited reduced colloid and increased oxidative stress. Although exposure to EHTBB and TBPH caused several physiological effects (e.g., heart and brain mass), only exposure to 50 ng g^-1 EHTBB appeared to reduce hatching success. Our results suggest these flame retardants may be hazardous for predatory birds. Future research should evaluate long-term survival and fitness consequences in birds exposed to these chemicals.

Natural variation in yolk fatty acids, but not androgens, predicts offspring fitness in a wild bird

BACKGROUND

In egg-laying animals, mothers can influence the developmental environment and thus the phenotype of their offspring by secreting various substances into the egg yolk. In birds, recent studies have demonstrated that different yolk substances can interactively affect offspring phenotype, but the implications of such effects for offspring fitness and phenotype in natural populations have remained unclear. We measured natural variation in the content of 31 yolk components known to shape offspring phenotypes including steroid hormones, antioxidants and fatty acids in eggs of free-living great tits (Parus major) during two breeding seasons. We tested for relationships between yolk component groupings and offspring fitness and phenotypes.

RESULTS

Variation in hatchling and fledgling numbers was primarily explained by yolk fatty acids (including saturated, mono- and polyunsaturated fatty acids) - but not by androgen hormones and carotenoids, components previously considered to be major determinants of offspring phenotype. Fatty acids were also better predictors of variation in nestling oxidative status and size than androgens and carotenoids.

CONCLUSIONS

Our results suggest that fatty acids are important yolk substances that contribute to shaping offspring fitness and phenotype in free-living populations. Since polyunsaturated fatty acids cannot be produced de novo by the mother, but have to be obtained from the diet, these findings highlight potential mechanisms (e.g., weather, habitat quality, foraging ability) through which environmental variation may shape maternal effects and consequences for offspring. Our study represents an important first step towards unraveling interactive effects of multiple yolk substances on offspring fitness and phenotypes in free-living populations. It provides the basis for future experiments that will establish the pathways by which yolk components, singly and/or interactively, mediate maternal effects in natural populations.

Heterogenous effects of father and mother age on offspring development

Maternal age has long been described to influence a broad range of offspring life-history traits, including longevity. However, relatively few studies have tested experimentally for the effects of paternal age and even fewer the potential interactive effects of father and mother age on offspring life-history traits from conception to death. To tackle these questions, I performed a factorial experimental design where I manipulated the age of both male and female field crickets (Gryllus bimaculatus) and subsequently assessed their effects over the offspring’s entire lifetime. I found that, despite coming from larger eggs, the embryos of old females grew up at a slower rate, took more time to develop, and showed lower hatching success than those of young females. Offspring postnatal viability was unaffected by female age but, at adulthood, the offspring of old females were bigger and lived shorter than those of young females. Male age effects were mostly present during offspring postnatal development as nymphs sired by old males having increased early mortality. Moreover, father age strongly influenced the development of offspring adult personality as revealed by the shyer personality of crickets sired by an old male. My results indicate that father and mother age at reproduction have different effects that affect offspring traits at different stages of their development. The results further suggest that father and mother age effects could be mediated by independent mechanisms and may separately influence the evolution of aging.

In ovo injection of black cumin (Nigella sativa) extract on hatching and post hatch performance of thermally challenged broiler chickens during incubation

The objective of this study was to investigate the effects in ovo injection of black cumin (BC) extract on chick's quality and response of thermally challenged broiler chickens. A total of 700 hatching eggs of broiler chickens (Marshall) were assigned to 7 treatments of 100 eggs each and incubated using the conventional protocol (37.8°C) for the first 10 d and then exposed to a high temperature (39.6°C) for 6 h daily from day 10 until day 18 of the incubation. At embryonic day 17.5, the eggs were randomly allotted to 7 treatment groups, viz.: eggs without in ovo injection (WA), eggs injected with 0.9% saline solution (SA), 3 mg ascorbic acid (AA), 2 mg BC (TB), 4 mg BC (FB), 6 mg BC (SB), and 8 mg BC (EB) extracts. Experiment was laid out in a Completely Randomized Design. After hatching, the chicks were reared separately according to in ovo treatments for 8 wk. Data were collected on hatchability, chick quality, internal organs, growth performance, plasma superoxide dismutase, malondialdehyde, and triiodothyronine (T₃). The results showed that the hatchability of the eggs in the AA group was similar to that of SB eggs and higher than that of the other treatment groups. The intestinal weights of SB and EB birds were significantly higher (P < 0.05) than those of TB, SA, and WA. The final weights of the birds of SB and AA were higher (P < 0.05) than those of other treatments. The feed conversion ratio of the birds of TB and FB was comparable to that of EB and WA but higher than that of SB and AA. At hatch, the creatinine of the birds in SA and WA was similar to that of EB, FB, and TB but higher (P < 0.05) than that of AA and SB. Also, the plasma malondialdehyde, T₃, and superoxide dismutase of SB and AA birds were better (P < 0.05) than those of the control groups. Overall, it was concluded that 6 mg of BC extract improved the antioxidant status and posthatch performance of thermally challenged broiler chickens.

Age-specific patterns of maternal investment in common gull egg yolk

While the general patterns of age-specific changes in reproductive success are quite well established in long-lived animals, we still do not know if allocation patterns of maternally transmitted compounds are related to maternal age. We measured the levels of yolk testosterone, carotenoids and vitamins A and E in a population of known-aged common gulls (Larus canus) and found an age-specific pattern in yolk lutein and vitamin A concentrations. Middle-aged mothers allocated more of these substances to yolk compared to young and old mothers. These results can be explained through differences in age-specific foraging, absorption or deposition patterns of carotenoids and vitamins into yolk. If these molecules play a role in antioxidant defence and immune modulation, our results suggest a possible physiological pathway underlying the age-specific changes in reproductive success of long-lived birds in the wild.

Oxidative stress does not differ in primary dermal fibroblasts isolated from fast-growing and control-growing Japanese Quail (Coturnix japonica)

Growth rate is a key life-history trait that influences fitness and shapes the physiology of organisms. Additionally, faster growing individuals of the same species seem to be burdened with higher whole-animal metabolism and higher cellular turnover rates, which may lead to increases in oxidative stress, though this fact remains controversial within the literature. Aerobic organisms are subjected to metabolic by-products known as reactive oxygen species (ROS), which can wreak havoc on macromolecules, such as structurally altering proteins and inducing mutations in DNA, among others. To combat accumulating damage, organisms have evolved endogenous antioxidants and can consume exogenous antioxidants to sequester ROS before they cause cellular damage. We used primary fibroblast cells isolated from control-growing and fast-growing Japanese Quail (Coturnix japonica Temminck and Schlegel, 1849) as a study model for the effects of differing growth rates on oxidative stress. We measured reduced glutathione (GSH) concentration, ROS production, mitochondrial content, and lipid peroxidation (LPO) damage. We found no significant differences in the four parameters measured between control-growing and fast-growing Quail. However, we found that in fast-growing Quail, GSH correlated with LPO damage and mitochondrial content, and LPO damage positively correlated with mitochondrial content, whereas control-growing Quail only showed positive relationships between LPO damage and ROS production.

Effects of calcium supplementation on oxidative status and oxidative damage in great tit nestlings inhabiting a metal-polluted area

Calcium has been proposed to diminish metal toxicity by the modulation of the oxidative stress. This study explores the effects of Ca availability and metal exposure on oxidative stress biomarkers in great tit (Parus major) nestlings. Nests were supplemented with Ca (Ca-supplemented group) or not supplemented (Control group) in a metal-polluted and a background zone in SW Finland. Metal concentrations were analyzed from feces. We analyzed antioxidants (tGSH, GSH:GSSG ratio, CAT, GST, GPx, SOD), protein carbonylation and lipid peroxidation in red cells of nestlings. Ca-supplemented and fast-growing nestlings showed higher CAT activity to cope with reactive oxygen species (ROS) generated during intensive growth and metabolism. SOD and GPx (the latter not statistically significant) were more active in the polluted area, possibly reflecting higher ROS production in nestlings from this zone due to the enhanced metal exposure and smaller size. Antioxidant levels changed over the range of metal concentrations depending on the Ca levels in plasma, suggesting that higher Ca levels stimulate antioxidants and mitigate the impacts of metals. Ca supplementation may improve nestling traits and reproductive output when antioxidants are enhanced in a situation of oxidative challenge. Therefore, Ca should be considered in future studies assessing metal exposure and effects on wild birds.

Significant differences in maternal carotenoid provisioning and effects on offspring fitness in Chinook salmon colour morphs

In oviparous species, maternal carotenoid provisioning can deliver diverse fitness benefits to offspring via increased survival, growth and immune function. Despite demonstrated advantages of carotenoids, large intra- and interspecific variation in carotenoid utilization exists, suggesting trade-offs associated with carotenoids. In Chinook salmon (Oncorhynchus tshawytscha), extreme variation in carotenoid utilization delineates two colour morphs (red and white) that differ genetically in their ability to deposit carotenoids into tissues. Here, we take advantage of this natural variation to examine how large differences in maternal carotenoid provisioning influence offspring fitness. Using a full factorial breeding design crossing morphs and common-garden rearing, we measured differences in a suite of fitness-related traits, including survival, growth, viral susceptibility and host response, in offspring of red (carotenoid-rich eggs) and white (carotenoid-poor eggs) females. Eggs of red females had significantly higher carotenoid content than those of white females (6× more); however, this did not translate into measurable differences in offspring fitness. Given that white Chinook salmon may have evolved to counteract their maternal carotenoid deficiency, we also examined the relationship between egg carotenoid content and offspring fitness within each morph separately. Egg carotenoids only had a positive effect within the red morph on survival to eyed-egg (earliest measured trait), but not within the white morph. Although previous work shows that white females benefit from reduced egg predation, our study also supports a hypothesis that white Chinook salmon have evolved additional mechanisms to improve egg survival despite low carotenoids, providing novel insight into evolutionary mechanisms that maintain this stable polymorphism.

Regulation of lipid peroxidation and ferroptosis in diverse species

This review by Conrad et al. reviews the functions and regulation of lipid peroxidation, ferroptosis, and the antioxidant network in diverse species, including humans, other mammals and vertebrates, plants, invertebrates, yeast, bacteria, and archaea, and discusses the potential evolutionary roles of lipid peroxidation and ferroptosis.

Lipid peroxidation is the process by which oxygen combines with lipids to generate lipid hydroperoxides via intermediate formation of peroxyl radicals. Vitamin E and coenzyme Q₁₀ react with peroxyl radicals to yield peroxides, and then these oxidized lipid species can be detoxified by glutathione and glutathione peroxidase 4 (GPX4) and other components of the cellular antioxidant defense network. Ferroptosis is a form of regulated nonapoptotic cell death involving overwhelming iron-dependent lipid peroxidation. Here, we review the functions and regulation of lipid peroxidation, ferroptosis, and the antioxidant network in diverse species, including humans, other mammals and vertebrates, plants, invertebrates, yeast, bacteria, and archaea. We also discuss the potential evolutionary roles of lipid peroxidation and ferroptosis.

Evaluation of pigeon egg yolk for post thaw quality, enzyme leakage and fertility of buffalo (Bubalus bubalis) bull spermatozoa

Egg yolk is used as a cryoprotectant in semen preservation. However, its composition varies according to the species which may influence its effectiveness during the freeze-thaw process. Therefore, study was conducted to identify the optimum level of pigeon egg yolk (PEY) in Tris citric acid (TCA) extender for freezability and in vivo fertility of buffalo semen. Semen was collected at weekly intervals for a period of three weeks (replicates) from 6 Nili Ravi buffalo bulls (2 ejaculates/bull/replicate) and diluted with TCA extender (50 × 10⁶ motile spermatozoa ml^-1) containing 5%, 10%, 15% and 20% PEY or 20% CEY (control) and cryopreserved. Post-thaw sperm quality and extracellular enzymes leakage was assessed after thawing. Sperm motility, plasma membrane integrity, livability and viability was significantly higher in extenders containing 10% and 15% PEY compared to 5% PEY, 20% PEY or 20% CEY (controls). A dose-dependent decrease was recorded in the chromatin damage for the PEY, being lowest for the 15% and 20% PEY which was significantly less compared to controls (20% CEY). The extracellular GOT and LDH leakage was significantly lower (P < 0.05) in extender containing 10% and 15% PEY compared to the controls. Semen collected from 2 bulls, cryopreserved in extenders containing 15% PEY or 20% chicken egg yolk was assessed for fertility after artificial inseminations. A total of 400 buffaloes were inseminated (100 inseminations/extender/bull). The overall fertility rate was significantly higher (P < 0.05) with semen cryopreserved in extender containing 15% PEY (56%) compared to 20% CEY (42%; controls). In conclusion, pigeon egg yolk at 15% offers advantages over 20% chicken egg yolk in terms of in vitro post-thaw semen quality and in vivo fertility of buffalo.

Experimental manipulation of dietary arsenic levels in great tit nestlings: Accumulation pattern and effects on growth, survival and plasma biochemistry

Arsenic (As) is a ubiquitous metalloid classified as one of the most hazardous substances, but information about its exposure and effects in free-living passerines is lacking. The aim of this study is to elucidate the effect of an As manipulation experiment on survival, growth and physiology of great tits (Parus major). Wild P. major nestlings inhabiting an unpolluted area were dosed with water, 0.2 or 1 μg g^-1 d^-1 of sodium arsenite (Control, Low and High As groups), whereas those living in a metal-polluted area were dosed with water (Smelter group). Birds accumulated As in tissues (liver, bone and feathers) in a dose-dependent way. Nestlings exposed to 1 μg g^-1 d^-1 of sodium arsenite showed reduced number of fledglings per successful nest, and those exposed to 0.2 μg g^-1 d^-1 had reduced wing growth, which could have post-fledging consequences such as increased predation risk. These results suggest that the LOAEL for effects on nestling survival and development in great tits is likely equal to or below 1 μg g^-1 d^-1. However, limited effects on the biochemical parameters evaluated were found. It has been shown that As may produce oxidative stress and tissue damage, so further research exploring this issue will be carried out in a future study.

Maternally derived yolk antioxidants buffer the developing avian embryo against oxidative stress induced by hyperoxia

In oviparous animals, maternally transferred antioxidants protect the embryo from oxidative damage from high rates of reactive oxygen species (ROS) production incurred by rapid growth. Elevated ROS exposure – beyond that incurred by normal growth - can occur as a result of exposure to exogenous factors (e.g. pollutants, toxins, radiation), increasing the risk of oxidative damage, with potentially adverse consequences for embryonic development and long-term fitness. The capacity of the avian embryo's antioxidant protection system to counter an increased exogenous oxidative threat is poorly understood. We induced an external oxidative challenge via experimental increase in ambient oxygen concentration throughout incubation of wild great tit Parus major eggs in the laboratory. At day 11 of incubation, brain tissue revealed no consistent differences in oxidative stress status – as measured by antioxidant levels (superoxide dismutase and total glutathione), lipid peroxidation and telomere length - between control (21% oxygen) and hyperoxic (40% oxygen) embryos. However, the level of vitamin E was significantly lower and lipid peroxidation was significantly higher in yolks of eggs reared under elevated oxygen concentrations. The results suggest that maternally derived yolk antioxidants successfully buffer developing embryonic tissues against an increased exogenous oxidative threat. Furthermore, vitamin E plays a more important role in protecting the embryo than carotenoids. However, the depletion of antioxidants and increased peroxidation of lipids in the yolk could have negative consequences for embryonic development – in particular for the brain and heart that require highly unsaturated fatty acids - and protection against the oxidative burst following hatching.

Thymol feed supplementation in quail alters the percentages of nutritionally relevant egg yolk fatty acids: effects throughout incubation

BACKGROUND

Polyunsaturated fatty acids (PUFA) are crucial components of egg yolk and particularly prone to oxidative damage, generating losses of nutrients for embryonic development and influencing the quality of eggs for human consumption. The aim of this study was to evaluate whether dietary thymol (a natural antioxidant) is related to changes in quail egg yolk total (T), triglyceride (TG) and phospholipid (PL) fatty acid composition at different stages of embryo development. Thus female Japanese quail (100 days of age) were assigned to one of two dietary treatments (12 individuals each): CON (basal diet) or THY (0.0016 mol thymol day^-1 per bird). After 2 weeks of supplementation, eggs were incubated and samples were obtained at 0, 4 and 16 days of embryonic development.

RESULTS

In 0 day THY eggs, α-linolenic acid and n-3 PUFA in T and TG, docosahexaenoic acid and PUFA in T and arachidonic acid in TG were increased, while saturated fatty acids (SFA) in T were reduced. From 4 days on, PUFA, n-3 PUFA and SFA from T and TG in THY eggs were found to be similar to those of CON eggs. The changes in PL throughout incubation were similar in both dietary treatments.

CONCLUSION

Thymol would provide the embryo with PUFA for synthesis/deposition in membranes and/or assign to supply energy. Additionally, thymol supplementation would be advisable for the production of healthier table eggs. © 2017 Society of Chemical Industry.

Co-adjustment of yolk antioxidants and androgens in birds

Mothers can shape the developmental trajectory of their offspring through the transmission of resources such as hormones, antioxidants or immunoglobulins. Over the last two decades, an abundant literature on maternal effects in birds has shown that several of these compounds (i.e. androgens, glucocorticoids and antioxidants) often influence the same offspring phenotypic traits (i.e. growth, immunity or oxidative stress levels), making interaction effects between egg components a likely scenario. However, the potential interactive effects of maternally transmitted compounds on offspring development and potential co-adjustment of these compounds within an egg are still poorly understood. Here, we report the results of an interspecific comparative analysis on birds' egg yolk composition (i.e. androgens and antioxidants) where we found that yolk carotenoid and vitamin E concentrations are positively associated, supporting the hypothesis that these two antioxidants act in synergy. The concentrations of vitamin E also increased with increasing concentrations of testosterone. This last result confirms the emerging idea that androgens and antioxidants are co-adjusted within eggs and that maternally transmitted antioxidants might limit the potential direct and indirect effects of prenatal exposure to high testosterone levels on oxidative stress.

Antioxidants and embryo phenotype: is there experimental evidence for strong integration of the antioxidant system?

Organisms have evolved complex defense systems against oxidative stress. Bird eggs contain maternally derived antioxidants that protect embryos from oxidative damage. The antioxidant system components are thought to be integrated, but few studies have analyzed the covariation between antioxidant concentrations, embryo ‘oxidative status’ and morphology. In addition, no study has tested the effects of experimental change in yolk antioxidant concentration on other antioxidants, on their reciprocal relationships and on their relationships with embryo oxidative status or growth, which are expected if antioxidants defenses are integrated. In yellow-legged gull (Larus michahellis) embryos, we analyzed the covariation between several antioxidants, markers of ‘oxidative status’ [total antioxidant capacity (TAC), concentration of pro-oxidants (TOS), lipid peroxidation (LPO) and protein carbonylation (PC)] in the yolk, liver and brain, and morphology. Yolk and liver antioxidant concentrations were positively correlated reciprocally and with embryo size, and positively predicted TAC but not oxidative status. TOS and LPO were positively correlated in the liver, while TAC and LPO were negatively correlated in the brain. Weak relationships existed between antioxidants and TOS, PC and LPO. The effects of antioxidants on oxidative status and morphology were non-synergistic. An experimental physiological increase in yolk vitamin E had very weak effects on the relationships between other antioxidants or oxidative status and vitamin E concentration, the concentration of other antioxidants or oxidative status; the covariation between other antioxidants and oxidative status, and relationships between morphology or oxidative status and other antioxidants, challenging the common wisdom of strong functional relationships among antioxidants, at least for embryos in the wild.

Extreme intra-clutch egg size dimorphism is not coupled with corresponding differences in antioxidant capacity and stable isotopes between eggs

Oviparous females need to allocate resources optimally to their eggs in order to maximize their fitness. Among these resources, dietary antioxidants, acquired by females and transferred to the eggs during egg formation, can greatly affect the development and survival of the embryo and chick. In crested penguins, incubation starts after the second and last egg is laid and, as opposed to many other bird species, this egg hatches first, thereby enhancing the survival of the chick. Here, we assessed whether antioxidant and isotopic composition could underlie these differences between eggs within clutches of southern rockhopper penguins (Eudyptes chrysocome chrysocome). The second-laid egg had higher total antioxidant capacity than the first-laid egg, although this was not due to higher antioxidant concentration but to its higher mass. This suggests that resources are allocated by females at a constant rate in both eggs within clutches. Accordingly, we found a strong correlation for isotopic compositions between eggs suggesting that resources were allocated similarly to each egg within the clutch. Overall, we found little evidence for a significant role of antioxidant and isotopic compositions to explain differences in terms of embryo/chick development between eggs in crested penguins. However, since our results suggest a constant rate of antioxidant transfer from females to eggs, limiting the mass of the first-laid egg might represent a strategy for females to spare antioxidant defences and preserve self-maintenance.

Incubation relative humidity induces renal morphological and physiological remodeling in the embryo of the chicken (Gallus gallus domesticus)

The metanephric kidneys of the chicken embryo, along with the chorioallantoic membrane, process water and ions to maintain osmoregulatory homeostasis. We hypothesized that changes in relative humidity (RH) and thus osmotic conditions during embryogenesis would alter the developmental trajectory of embryonic kidney function. White leghorn chicken eggs were incubated at one of 25-30% relative humidity, 55-60% relative humidity, and 85-90% relative humidity. Embryos were sampled at days 10, 12, 14, 16, and 18 to examine embryo and kidney mass, glomerular characteristics, body fluid osmolalities, hematological properties, and whole embryo oxygen consumption. Low and especially high RH elevated mortality, which was reflected in a 10-20% lower embryo mass on D18. Low RH altered several glomerular characteristics by day 18, including increased numbers of glomeruli per kidney, increased glomerular perfusion, and increased total glomerular volume, all indicating potentially increased functional kidney capacity. Hematological variables and plasma and amniotic fluid osmolalities remained within normal physiological values. However, the allantoic, amniotic and cloacal fluids had a significant increase in osmolality at most developmental points sampled. Embryonic oxygen consumption increased relative to control at both low and high relative humidities on Day 18, reflecting the increased metabolic costs of osmotic stress. Major differences in both renal structure and performance associated with changes in incubation humidity occurred after establishment of the metanephric kidney and persisted into late development, and likely into the postnatal period. These data indicate that the avian embryo deserves to be further investigated as a promising model for fetal programming of osmoregulatory function, and renal remodeling during osmotic stress.

Effects of experimental calcium availability and anthropogenic metal pollution on eggshell characteristics and yolk carotenoid and vitamin levels in two passerine birds

The maternal investment into egg quality depends on the condition of the female, the quality of the mate, and the quality of the environment. In that sense, availability of nutrients and exposure to pollutants are essential parameters to consider. The main aim of this study is to assess the effects of calcium (Ca) availability and anthropogenic metal pollution on early-stage reproduction in two passerine species, great tits (Parus major) and pied flycatchers (Ficedula hypoleuca), inhabiting a Ca-poor and metal-polluted area in SW Finland. Both species were able to obtain sufficient Ca for eggshell formation, and metal pollution was below the level of having negative effects in the egg size and eggshell characteristics. However, metal polluted environment negatively affected yolk lutein and vitamin D3 levels in both species, probably because of a lower access to carotenoid-rich diet and higher metal interference with vitamin D3 metabolism. The higher levels of vitamin D3 in yolks in the unpolluted zone could also be due to upregulated D3 levels as a response to the lower natural Ca availability. Yolk carotenoids and vitamin D3 were positively associated with nestling growth and size, supporting their importance for the appropriate chick development. The interspecific differences in yolk nutrient concentrations possibly reflect the different growth rate of these species. Pied flycatchers are likely adapted to low Ca availability through an efficient vitamin D3 metabolism, but their Ca intake could be close to a deficient level.

Antioxidant systems in chick embryo development. Part 1. Vitamin E, carotenoids and selenium

Chick viability is known to be an important factor determining profitability of the poultry industry. Chick embryo tissues contain a high proportion of highly polyunsaturated fatty acids in the lipid fraction and therefore need antioxidant defence. The antioxidant system of the developing embryo and newly hatched chick includes the antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase), water-soluble antioxidants (ascorbic acid, taurine, carnitine, glutathione, etc.), fat-soluble antioxidants (vitamin E, carotenoids, coenzyme Q) as well as selenium (Se). In fact, the high levels of endogenous antioxidants within the egg and embryonic tissues can clearly serve as a major adaptive mechanism for the protection of the tissue during the oxidative stress experienced at hatching. It has been shown that among different nutrients in the maternal diet which could significantly affect chick embryo development and their viability in the early posthatch life, natural antioxidants have been suggested to play a central role. Our data indicate that increased supplementation of the maternal diet can substantially increase concentrations of vitamin E, carotenoids (especially canthaxanthin) and Se in developing chick tissues and significantly decrease susceptibility to lipid peroxidation being effective nutritional tools to deal with various commercial stresses in poultry production.