Estrogen receptor-alpha populations change with age in commercial laying hens

Quercetin-based treatment improves eggshell quality in aged laying hens by modulating immune response, eggshell gland health and serum metabolome

BACKGROUND

Eggshell quality is a critical determinant of egg product value and consumer preference. Deficient eggshells increase breakage susceptibility, leading to economic losses and reduced marketability. Dietary interventions hold promise for improving eggshell quality. Quercetin, a naturally occurring flavonoid, exhibits diverse biological activities relevant to eggshell formation. These include antioxidant and anti-inflammatory properties, and potential modulation of estrogen levels, which are known to influence eggshell quality.

RESULTS

A total of 160 46-week-old laying hens were randomly divided into two groups, with 8 replicates in each group and 10 chickens in each replicate. The control group was fed a corn-soybean meal basal diet, while the experimental group received a basal diet supplemented with 300 mg kg-1 quercetin. The trial period lasted for 10 weeks. The study showed that dietary supplementation with quercetin significantly increased eggshell thickness (P < 0.001). Eggshell ultrastructure analysis revealed significant increases in effective layer thickness (P < 0.001) and a marked decrease in the thickness ratio of the mammillary layer to total eggshell thickness (P < 0.001) with quercetin supplementation. Serum analysis indicated significantly higher levels of immunoglobulin A, immunoglobulin G, estrogen receptors and carbonic anhydrase-2 in hens supplemented with quercetin compared to controls (P < 0.05). Furthermore, quercetin supplementation reduced tubular gland edema and improved villus height, luminal epithelial cell height and gland duct diameter (P < 0.05). Quantitative real-time PCR analysis showed that quercetin supplementation altered immune responses in the liver, spleen and oviduct. Notably, quercetin supplementation increased metabolites associated with glycine, serine and threonine metabolism. These amino acids, key precursors of eggshell matrix proteins, showed increased metabolism, suggesting a potential mechanism by which quercetin supports eggshell biomineralization.

CONCLUSION

This study suggests that compromised eggshell quality might be associated with impaired biomineralization function in the eggshell gland, potentially due to tissue damage. Conversely, dietary quercetin supplementation significantly increased eggshell thickness. We propose a potential mechanism involving the activation of glycine, serine and threonine metabolic pathways, which might enhance the biomineralization capacity and overall health of the eggshell gland. © 2025 Society of Chemical Industry.

Exploration of age-related changes in reproductive parameters of female Japanese quail (Coturnix japonica)

The decline in reproductive efficiency during post-peak period of production in poultry species holds significant economic implications. This study aimed to investigate the productive and reproductive performance of Japanese quails across distinct production stages and the association between these parameters and some genes expression and histometric alterations within the reproductive system. A total of 180 quails from a commercial flock were selected at varying egg production stages, including young, mature, and old, with 45 female and 15 male quails allocated to each group. The quails were maintained for six weeks. During recording period, daily records of egg production and egg weight were recorded. Additionally, oviduct histometric and Follicle biometric measurements, along with mRNA transcript abundance assessments related to follicular selection and yolk accumulation, were conducted on the oviduct, ovary, and small yellow follicles at the end of the experimental period. The results revealed a decrease in egg production in the old group compared to the young and mature groups (P < 0.05); meanwhile, the old group had the highest egg weight, and F1 follicle weight (P < 0.05). Additionally, the number of prehierarchical follicles was lower in the mature and old groups compared to the young group (P < 0.05). The lowest oviduct length, primary and secondary fold height, and thickness of the isthmus and magnum were noted in the old group (P < 0.05). Fertility and hatchability were lower in the old group compared to the other groups (P < 0.05). The mRNA transcript abundance of anti-Mullerian hormone (AMH), was highest in the old group and lowest in the young group (P < 0.05), while the mRNA transcript abundance of bone morphogenetic protein 15 (BMP15) was higher in the mature group compared to the other groups (P < 0.05). Additionally, the young quails had the highest occludin (OCLN) mRNA transcript abundance compared to other groups (P < 0.05). Overall, the study findings indicate decreased production and reproductive performance, as well as reduced hatchling quality over the production period, attributed to a declining number of follicles, noncooperative gene expression related to follicle selection and yolk accumulation, and diminishing oviduct fold size.

Dietary supplementation with calcitriol or quercetin improved eggshell and bone quality by modulating calcium metabolism

This study was aimed to investigate the effects of dietary calcitriol or quercetin supplementation on eggshell and bone quality of laying hens. In trial 1, 72 Hy-Line Brown layers (80-week-old) with weak-shelled strength (25 to 30 N) were assigned into 4 dietary treatments with 6 replicates of 3 birds and fed a basal diet (4% calcium level) or basal diets supplemented with 0.5% calcium, 5 μg/kg calcitriol or 500 mg/kg quercetin for 4 weeks. In trial 2, 360 Hy-Line Brown layers (60-week-old) were divided into 3 groups with 8 replicates of 15 birds: control group (basal diet), calcitriol group (basal diet + 5 μg/kg calcitriol), and quercetin group (basal diet + 500 mg/kg quercetin). This trial lasted for 12 weeks. The results showed that dietary calcitriol or quercetin improved eggshell quality in both trials (P < 0.05). In trial 2, compared with the control group, both calcitriol and quercetin supplementations improved femoral bone quality, calcium retention of hens and calcium content in uterine fluid at 18.5 h post-oviposition (PO) (P < 0.05), along with enhancing uterine morphology. Compared to the control group, supplemental calcitriol or quercetin up-regulated the relative mRNA expression levels of uterine transient receptor potential cation channel, subfamily V, member 6 (TRPV6) at 8.5 h PO and plasma membrane calcium-ATPase (PMCA), vitamin D receptor (VDR), estrogen receptor alpha (ERα) at 18.5 h PO (P < 0.05), but down-regulated the uterine caspase 3 (CASP3) relative mRNA expression level at 8.5 h PO (P < 0.05). Meanwhile, the femoral relative mRNA expression levels of tartrate-resistant acid phosphatase (TRAP) (up-regulated at 8.5 and 18.5 h PO) and alkaline phosphatase (ALP) (up-regulated at 8.5 h PO but down-regulated at 18.5 h PO) were also affected by calcitriol or quercetin supplementation (P < 0.05). Compared to the calcitriol, quercetin increased hen-day egg production and femoral medullary bone volume/bone tissue volume but reduced femoral stiffness (P < 0.05), which were accompanied by increased relative mRNA expression levels of uterine TRPV6, estrogen receptor beta (ERβ) at 18.5 h PO (P < 0.05). Overall, both dietary calcitriol and quercetin could improve eggshell and bone quality by modulating calcium metabolism of aged layers. Compared to calcitriol, dietary quercetin up-regulated the expression of uterine calcium transporters, without affecting eggshell quality.

Dietary silymarin improves performance by altering hepatic lipid metabolism and cecal microbiota function and its metabolites in late laying hens

BACKGROUND

Liver lipid dysregulation is one of the major factors in the decline of production performance in late-stage laying hens. Silymarin (SIL), a natural flavonolignan extracted from milk thistle, is known for its hepatoprotective and lipid-lowering properties in humans. This study evaluates whether SIL can provide similar benefits to late-stage laying hens. A total of 480 68-week-old Lohmann Pink laying hens were randomly assigned into 5 groups, each group consisting of 6 replicates with 16 hens each. The birds received a basal diet either without silymarin (control) or supplemented with silymarin at concentrations of 250, 500, 750, or 1,000 mg/kg (SIL250, SIL500, SIL750, SIL1000) over a 12-week period.

RESULTS

The CON group exhibited a significant decline in laying rates from weeks 9 to 12 compared to the initial 4 weeks (P = 0.042), while SIL supplementation maintained consistent laying rates throughout the study (P > 0.05). Notably, the SIL500 and SIL750 groups showed higher average egg weight than the CON group during weeks 5 to 8 (P = 0.049). The SIL750 group had a significantly higher average daily feed intake across the study period (P < 0.05), and the SIL500 group saw a marked decrease in the feed-to-egg ratio from weeks 5 to 8 (P = 0.003). Furthermore, the SIL500 group demonstrated significant reductions in serum ALT and AST levels (P < 0.05) and a significant decrease in serum triglycerides and total cholesterol at week 12 with increasing doses of SIL (P < 0.05). SIL also positively influenced liver enzyme expression (FASN, ACC, Apo-VLDL II, FXR, and CYP7A1; P < 0.05) and altered the cecal microbiota composition, enhancing species linked to secondary bile acid synthesis. Targeted metabolomics identified 9 metabolites predominantly involved in thiamin metabolism that were significantly different in the SIL groups (P < 0.05).

CONCLUSIONS

Our study demonstrated that dietary SIL supplementation could ameliorate egg production rate in late stage laying hens, mechanistically, this effect was via improving hepatic lipid metabolism and cecal microbiota function to achieve. Revealed the potentially of SIL as a feed supplementation to regulate hepatic lipid metabolism dysregulation. Overall, dietary 500 mg/kg SIL had the best effects.

Effect of tamoxifen treatment on catalase (CAT) and superoxide dismutase (SOD) expression and localization in the hen oviduct

The imbalance between free reactive oxygen species (ROS) generation and removal (e.g., by antioxidative enzymes) leads to the damage of important biomolecules and cells. Earlier studies in hens showed that treatment with tamoxifen (TMX; estrogen receptor inhibitor) modulates oxidative stress and causes the reproductive system regression realized by cell apoptosis. The aim of the present study was, therefore, to examine the expression and immunolocalization of the key enzymatic antioxidants, i.e. catalase (CAT) and superoxide dismutase (SOD), in the chicken oviduct following TMX treatment. Laying hens were treated daily with TMX until a pause in egg-laying occurred and then euthanized on day 8 of the experiment. Quantitative real-time PCR and western blot analyses showed the presence of CAT and SOD transcripts and proteins, respectively, in all oviductal segments, i.e., the infundibulum, magnum, isthmus, shell gland and vagina. In control hens (laying), the mRNA expression of CAT was the highest in the shell gland, lower in the isthmus and the lowest in other oviductal parts, whereas protein expression was the highest in the magnum, lower in the isthmus and the lowest in other segments. The SOD transcript and protein abundances only were lower in the magnum than in other segments. Immunoreactive CAT and SOD products were localized in all layers of the oviductal wall, but the intensity of staining depended on the cell type. TMX treatment affected CAT and SOD expression and the effect of TMX depended on gene, protein, cell type and oviductal part. Generally, CAT expression was elevated, while SOD expression was decreased under TMX treatment. These results point to the importance of CAT and SOD in the maintenance of proper oviduct health and function. Changes in ROS scavenging enzymes after estrogen receptor blockage indicate the significance of estrogen in the regulation of oxidative status in the avian oviduct.

Estradiol-17ß Is Influenced by Age, Housing System, and Laying Performance in Genetically Divergent Laying Hens (Gallus gallus f.d.)

The estrogen estradiol-17ß is known as one of the major gonadal steroid hormones with different functions in reproduction. In this study we analyzed estradiol-17ß concentration in laying hens of four pure bred chicken laying lines at four different time intervals of the laying period (17th-19th week of age, 33rd-35th week of age, 49th-51st week of age, and 72nd week of age). The high performing white egg (WLA) and brown egg (BLA) layer lines as well as the low performing white (R11) and brown (L68) layer lines were kept in both single cages and a floor housing system. We investigated whether there were differences in estradiol -17ß concentrations between lines at different ages that could be related to selection for high egg production or phylogenetic origin of the animals, and whether there was an influence of housing conditions on estradiol-17ß. Estradiol-17ß concentrations differed between high and low performing layer lines at all time intervals studied. High performing hens showed higher estradiol-17ß concentrations compared to low performing hens. In all lines, highest estradiol-17ß concentration was measured at their 49th to their 51st week of age, whereas the peak of laying intensity was observed at their 33rd to their 35th week of age. Additionally, hens with fewer opportunities for activity housed in cages showed higher estradiol-17ß concentrations than hens kept in a floor housing system with more movement possibilities. We could show that laying performance is strongly linked with estradiol -17ß concentration. This concentration changes during laying period and is also influenced by the housing system.

The Diverse Roles of 17β-Estradiol in Non-Gonadal Tissues and Its Consequential Impact on Reproduction in Laying and Broiler Breeder Hens

Estradiol-17β (E2) has long been studied as the primary estrogen involved in sexual maturation of hens. Due to the oviparous nature of avian species, ovarian production of E2 has been indicated as the key steroid responsible for activating the formation of the eggshell and internal egg components in hens. This involves the integration and coordination between ovarian follicular development, liver metabolism and bone physiology to produce the follicle, yolk and albumen, and shell, respectively. However, the ability of E2 to be synthesized by non-gonadal tissues such as the skin, heart, muscle, liver, brain, adipose tissue, pancreas, and adrenal glands demonstrates the capability of this hormone to influence a variety of physiological processes. Thus, in this review, we intend to re-establish the role of E2 within these tissues and identify direct and indirect integration between the control of reproduction, metabolism, and bone physiology. Specifically, the sources of E2 and its activity in these tissues via the estrogen receptors (ERα, ERβ, GPR30) is described. This is followed by an update on the role of E2 during sexual differentiation of the embryo and maturation of the hen. We then also consider the implications of the recent discovery of additional E2 elevations during an extended laying cycle. Next, the specific roles of E2 in yolk formation and skeletal development are outlined. Finally, the consequences of altered E2 production in mature hens and the associated disorders are discussed. While these areas of study have been previously independently considered, this comprehensive review intends to highlight the critical roles played by E2 to alter and coordinate physiological processes in preparation for the laying cycle.

Dietary mulberry-leaf flavonoids improve the eggshell quality of aged breeder hens

Eggshell quality is subject to a significant decline in the late laying period, which results in huge economic losses. The purpose of this study was to investigate the effects of dietary mulberry-leaf flavonoids (MF) on the eggshell quality of aged breeder hens. A total of 270 (60-week-old) Qiling breeder hens were randomly assigned to 3 treatments with supplemental dietary MF doses (0, 30, and 60 mg/kg). The results showed that dietary MF improved the eggshell thickness and strength, following the reduced broken egg ratio (P < 0.05). Histological analysis showed that dietary MF increased glandular density and luminal epithelium height in the shell gland (P < 0.05). MF treatment reduced the apoptotic index of the shell gland, following by improved antioxidant capacity (P < 0.05). The protein expression of Caspase 3 was down-regulated, and Nrf2 was up-regulated by dietary MF (P < 0.05). Furthermore, calcium (Ca) content in the serum and shell gland, as well as the activity of Ca²⁺-ATPase in the shell gland were increased by dietary MF (P < 0.05). Ca transport-related genes (ESRα, ESRβ, KCNA1, OPN, CABP-28K and CDH6) in the shell gland were upregulated by dietary MF treatment (P < 0.05). In conclusion, dietary MF could ameliorate the eggshell quality of aged hens by improving antioxidative capability and Ca deposition in the shell gland of uterus.

Royal Jelly Improves the Morphology of the Reproductive Tract, Internal Egg Quality, and Blood Biochemical Parameters in Laying Hens at the Late Stage of Production

The purpose of this study was to evaluate the effects of royal jelly (RJ) on the morphology of the reproductive tract, egg production, and blood biochemical indices of aged laying hens. In total, 120 Lohman Brown laying hens at week 58 of age were randomly assigned into three equal groups. Pure RJ was dissolved in distilled water and injected subcutaneously as follows: the first treatment (R₁; 100 mg RJ kg^-1); the second treatment (R₂; 200 mg RJ kg^-1); the control treatment (CON; 1 mL distilled water). Both RJ-treated groups exhibited a significantly higher number of large yellow follicles (LYFs), small yellow follicles (SYFs), and large white follicles (LWFs) (p ˂ 0.05). Furthermore, RJ treatment significantly increased the diameter and weight of the F1 follicles. However, only the R2 group exhibited significantly greater ovary and uterus weights. RJ treatment did not affect the percentage of oviduct and weight of ovarian stroma. In addition, RJ increased the hen-day egg production rate compared with the CON group; however, only the R₂ group showed greater egg weight (p = 0.032). RJ treatment also improved the albumen height, Haugh units, and yolk index. The administration of RJ significantly decreased the serum glucose, but increased the levels of serum albumen and cholesterol. In conclusion, RJ treatment may improve the morphology of the reproductive tract (including follicular growth and oviduct morphology), egg production rate, and internal egg quality traits of aged laying hens.

Molting method alternative and detection of estrogen receptors by immunohistochemical methods on molted layers

Three experiments were designed to evaluate the effects of different molting methods on the growth performance, detection of estrogen receptors (ERs), and immunohistochemical properties of some tissues in pre-, during, and post-molting of layers. In experiment 1, 302 Hy-line W-36 were reared from 75 to 76 weeks. In experiment 2, a total of 252 Hy-line W-36 were randomly allocated to 7 groups, with 6 replications and 6 birds in each. Hens fed in the E and D groups reached 30% of loss weight sooner (P < 0.05). Egg production was also sooner stopped in the FW group than in other ones (P < 0.05). In experiment 3, after inducing molting, each group in experiment 2 was divided into 2 groups with and without Humulus lupulus (Hop). The E group feed intake was increased, as compared to groups F and C (P < 0.05). A significant increase in egg weight was found by applying Hop and molting methods (P < 0.05). Days for return to the initial egg production and 10% egg laying were significantly decreased in the birds fed by Hop in the E and D groups (P < 0.05). The W-D, N-D, W-E, and N-E groups sooner returned to 50% egg laying, in comparison to other treatments (P < 0.05). Plasma estrogen and ERs were decreased by the molting programs, as compared with pre-molting; however, Hop increased their post-molting. After the molting period, egg production and ERs were increased significantly, as compared with the pre-molting period. To conclude, the white button mushroom residual, through decreasing ERs, could be used successfully for forced molting, and Hop could lead to a good performance by increasing ERs in the second laying cycle.

Increased expression of fibroblast growth factor 23 is the signature of a deteriorated Ca/P balance in ageing laying hens

The present study concerned the effect of ageing in laying hens, from 23 to 90 weeks of age, on the regulation of Ca metabolism related to the requirement for eggshell mineralization. Samples were collected from parathyroid gland (PG), liver, jejunum, medullary bone (MB) and kidney for a quantitative study of candidate gene expression. Although parathyroid hormone (PTH) gene expression in the PG did not vary with age, a stronger challenge to Ca homeostasis was suggested in aged hens. Indeed gene expression of Ca transporters , Vitamin D Receptor (VDR) in the jejunum, and that of transient receptor potential channel subfamily V member 5 (TRPV5) in the kidney decreased. This could exacerbate bone resorption and impair bone accretion, as attested by a higher expression of the Carbonic Anhydrase 2 (CA2) gene and a lower expression of collagen type I alpha 1 chain (COL1A1) in the MB. The increased expression of Fibroblast Growth Factor 23 (FGF23) in the MB likely contributed to the decreased plasma levels of 1.25(OH)₂D₃ and the altered expression of target genes under its regulation. Our data highlights the molecular mechanisms underlying the osteoporotic syndrome previously documented in aged laying hens, thus providing new perspectives for future interventions.

The impact of phytoestrogen source supplementation on reproductive performance, plasma profile, yolk fatty acids and antioxidative status in aged laying hens

The objectives of this study were to investigate the effects of flaxseeds and/or fenugreek seeds as a source of phytoestrogens in laying feed on productive performance, egg quality, yolk fatty acids, plasma profile and antioxidative status in aged laying hens. A total of 120 Bovans Brown hens at 65 weeks of age were housed individually in laying cages in an open-sided building under a 16-hr light: 8-hr dark lighting schedule. Hens were randomly divided into four experimental treatments (n = 30 each): (a) control (basal diet without any supplementation); (b) 1 g/kg of flaxseeds; (c) 1 g/kg of fenugreek seeds; and (d) combination of 1 g/kg flaxseeds and 1 g/kg fenugreek seeds from 65 to 71 weeks of age. Hen-day egg production and egg mass were significantly increased by dietary supplementation of flaxseeds and/or fenugreek seeds, while feed intake was not affected; thus, feed conversion ratio was improved (p < 0.05). Weights of egg, albumen, yolk and shell were increased by the dietary treatments. Shell thickness and yolk colour were improved by supplementation of flaxseeds and/or fenugreek seeds. Yolk crude protein was not significantly affected by treatments; however, crude fat and calcium contents in yolk were increased and egg yolk cholesterol content was decreased. Interestingly, dietary supplementation of flaxseeds, fenugreek seeds and their combination had a significant positive effect on plasma luteinizing hormone, follicle-stimulating hormone, oestradiol-17β and triglycerides. Inclusion of flaxseeds and/or fenugreek seeds in the diets enhanced the serum glutathione peroxidase and superoxide dismutase activities and reduced the malondialdehyde and total cholesterol concentrations in plasma. Dietary supplementation of flaxseeds and/or fenugreek seeds increased α-linolenic and linoleic acids in egg yolk. It could be concluded that inclusion of mixed sources of phytoestrogens in diets improved laying performance, egg quality, the antioxidative status, hormonal profile and steroidogenesis in aged laying hens.

Age-related changes in the shell gland and duodenum in relation to shell quality and bone strength in commercial laying hen hybrids

Background

During the production period of laying hens, the number of cracked eggshells increases and the skeleton becomes brittle. Both these problems are related to ageing of the hen and cause economic problems for egg producers and impaired animal welfare. This study investigated key factors in the shell gland and duodenum related to eggshell quality and bone strength in laying hens during the production period. Five Lohmann Selected Leghorn (LSL) and five Lohmann Brown (LB), common hybrids in commercial egg production, were euthanized at 21, 29, 49 and 70 weeks (wk) of age. Blood samples for analysis of total calcium were taken at euthanization. Right femur and humerus were used for bone strength measurements and tissue samples from shell gland and duodenum were processed for morphology, immunohistochemical localisation of oestrogen receptors (ERα, ERβ), plasma membrane calcium ATPase (PMCA) and histochemical localisation of carbonic anhydrases (CA). Eggs were collected for shell quality measurements.

Results

At age 49 week, shell and bone strength had both deteriorated, but the hens were then able to maintain the level until 70 week of age and femur bone strength even improved. The main physiological findings associated with the effects seen at 49 week were reduced gland density and a shift in balance between ERα and ERβ in the shell gland, which coincided with a reduction in CA activity in the duodenum. Somewhat surprisingly, capillary density and capillaries with CA activity both increased in the shell gland over time, the latter possibly mediated via ERβ. These findings were independent of hybrid. PMCA was found in both shell gland and duodenum, but appeared unrelated to the age-related changes in shell and bone quality.

Conclusions

In hens around half-way through the production period, both shell quality and bone strength had deteriorated. Decreased gland density and a shift in the balance between ERα and ERβ in the shell gland, co-occurring with a dramatic drop in duodenal CA activity, are suggested as possible factors involved in age-related changes in shell and bone quality.

Electronic supplementary material

The online version of this article (10.1186/s13028-019-0449-1) contains supplementary material, which is available to authorized users.

Alterations in apoptotic markers and egg-specific protein gene expression in the chicken oviduct during pause in laying induced by tamoxifen

The aim of this study was to examine the cell apoptosis, gene expression and activity of caspases 2, 3, 8 and 9, and the mRNA expression of selected egg-specific proteins in the chicken oviduct during pause in egg laying induced by tamoxifen (TMX) treatment. The experiment was carried out on Hy-Line Brown laying hens. The control birds were treated subcutaneously with vehicle (ethanol) and the experimental ones with TMX at a dose of 6 mg/kg of body weight. Hens were treated daily until a pause in egg laying occurred and sacrificed on Day 7 of the experiment. Within the oviductal wall, the highest number of apoptotic cells (TUNEL-positive) was found in the luminal epithelium and the lowest in the stroma. The administration of TMX increased the percentage of apoptotic cells in the magnum, isthmus, and shell gland as well as immunoreactivity for caspases 3 and 9. Real-time PCR analysis revealed the segment-dependent mRNA expression of caspases 2, 3, 8 and 9. Treatment of hens with TMX elevated the level of caspase-2 transcript in the infundibulum, caspases 2, 3 and 8 in the isthmus, and caspase-9 in the shell gland (P < 0.05 - P < 0.001). As shown by fluorometric method TMX caused an increase in the activity of caspases 3 and 8 in the magnum, isthmus and shell gland, and the activity of caspases 2 and 9 in the isthmus and shell gland (P < 0.05 - P < 0.01). The expression of ovalbumin, avidin and ovocleidin-116 mRNAs was decreased (P < 0.05 - P < 0.001), ovocalyxin-36 mRNA level tended to increase, and ovocalyxin-32 expression was not affected by TMX. The results obtained indicate that caspases are involved in the chicken oviduct regression during a pause in laying induced by TMX, and estrogen is involved in the regulation of examined caspase expression and activity. The changes in mRNA transcript levels of some examined egg-specific proteins after TMX treatment suggest that there is a relationship between estrogen action and the expression of these genes.

Modelling the egg components and laying patterns of broiler breeder hens

There is scant information about the reproductive process in broiler breeders, with which to develop a feeding strategy that will be economically optimal for these birds. This study aimed to model the egg production of a flock of broiler breeder hens, using non-isometric equations. The number of eggs produced by 60 broiler breeder hens aged 24–60 weeks was monitored, as was the weight of these eggs and the weights of the components, yolk, albumen and shell. Oviposition sequences and the number and length of pauses between sequences were analysed. Non-isometric functions were applied to predict the weight of the egg; yolk weight was predicted from the age of the hen, while albumen and shell weights were predicted from yolk weight; and egg weight was obtained by summing the component weights. The incidence of soft-shelled and double-yolk eggs was also determined. Yolk weight (YW, g) can be described as YW = 18.03 × (1 – e–0.015 × (t – 103.4)) × e(0.001 × t), where t is the age of the bird (days). The weights of albumen (AW) and shell (SW) were based on YW predictions as follows: AW = 14.38 × YW0.375 and SW = 0.358 × (YW + AW)0.687. The rate of double-yolk egg (DY) production is described by DY = 2.28 × e(0.209 × TFE), and the rate of soft-shelled egg (SS) production by SS = 1.126 + 0.148/(1 – 0.024 × TFE) – 0.056 × TFE, as a function of time from first egg (TFE). On the basis of the results obtained, the model developed here is an accurate reflection of the changes that occur in the number of eggs produced by broiler breeders, as well as in the egg itself and in its components over the entire laying period. This model can thus be used in predicting the nutrient requirements of individual broiler breeder hens, which, when combined with simulated data from a large number of individuals, will accurately describe the laying performance of a flock of broiler breeders.

Dietary supplementation of Gracilariopsis persica is associated with some quality related sera and egg yolk parameters in laying quails

BACKGROUND

Gracilariopsis persica (Gp) is one of the most abundant red algae distributed in the Persian Gulf, containing various bioactive components with hypolipedimic, hypoglycemic and antioxidant properties. Therefore using laying quails as a model we aimed to investigate the effect of dietary Gp on body weight, feed conversion, estradiol, progesterone, calcium and lipid levels in serum, as well as the high-density:low-density lipoprotein (HDL:LDL) ratio. Yolk cholesterol and yolk lipid oxidation were also evaluated. To accomplish this, diets containing 0, 10, 30 and 50 g kg(-1) Gp were fed to 5-week-old laying quails for 12 weeks.

RESULTS

Our data revealed that Gp had no effect on body weight, feed conversion, triglycerides and estradiol levels of serum. Dietary Gp decreased the serum and yolk cholesterol in a dose-dependent manner. In addition, the sera progesterone and calcium levels and HDL:LDL ratios were increased by feeding diets containing 50 g kg(-1) Gp. Our results relating to yolk lipid oxidation showed that malondialdehyde content was decreased in Gp-fed laying quails.

CONCLUSIONS

The results of the present study demonstrate that not only serum and egg yolk cholesterol levels, but also susceptibility of yolk lipids to oxidation, can be decreased by feeding Gp to laying quails.

Exogenous estradiol improves shell strength in laying hens at the end of the laying period

Background

Cracked shells, due to age related reduction of shell quality, are a costly problem for the industry. Parallel to reduced shell quality the skeleton becomes brittle resulting in bone fractures. Calcium, a main prerequisite for both eggshell and bone, is regulated by estrogen in a complex manner. The effects of estrogen, given in a low continuous dose, were studied regarding factors involved in age related changes in shell quality and bone strength of laying hens. A pellet containing 0.385 mg estradiol 3-benzoate (21-day-release) or placebo was inserted subcutaneously in 20 birds each of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) at 70 weeks of age. Eggs were collected before and during the experiment for shell quality measurements. Blood samples for analysis of total calcium were taken three days after the insertion and at sacrifice (72 weeks). Right femur was used for bone strength measurements and tissue samples from duodenum and shell gland were processed for morphology, immunohistochemical localization of estrogen receptors (ERα, ERβ), plasma membrane calcium ATPase (PMCA) and histochemical localization of carbonic anhydrase (CA).

Results

Estrogen treatment increased shell thickness of both hybrids. In addition, shell weight and shell deformation improved in eggs from the brown hybrids. The more pronounced effect on eggs from the brown hybrid may be due to a change in sensitivity to estrogen, especially in surface epithelial cells of the shell gland, shown as an altered ratio between ERα and ERβ. A regulatory effect of estrogen on CA activity, but not PMCA, was seen in both duodenum and shell gland, and a possible connection to shell quality is discussed. Bone strength was unaffected by treatment, but femur was stronger in LSL birds suggesting that the hybrids differ in calcium allocation between shell and bone at the end of the laying period. Plasma calcium concentrations and egg production were unaffected.

Conclusions

A low continuous dose of estrogen improves shell strength but not bone strength in laying hens at the end of the laying period.

Uterine fluid proteins and egg quality characteristics for 2 commercial and 2 heritage laying hen lines in response to manipulation of dietary calcium and vitamin D3

The aim of this study was to evaluate the quality of eggs from 2 selected commercial strains of laying hens and 2 unselected lines of chickens fed diets with different combinations of Ca and vitamin D and relate it to the profile of uterine proteins and ultrastructure of the shell. A group of 4 chickens was housed in each of 24 cages. The group consisted of one representative from each of the following breeds: Lohmann LSL- Lite, Lohmann Classic-Brown, Fayoumi, and Light Sussex. Six dietary combinations of Ca and vitamin D(3) (3.35%, 2,500 IU; 4.10%, 2,500 IU (control); 4.85%, 2,500 IU; 3.35%, 200 IU; 4.10%, 200 IU; and 4.85%, 200 IU) were randomly assigned to 4 replicate cages for 2 treatment periods (26-29 and 56-59 wk of age). Data were analyzed as a split-plot design with cage as the main plot and hen as the subplot. Egg quality traits were different (P < 0.0001) between commercial and heritage breeds. Lohmann Brown had stronger shells with higher specific gravity compared with other breeds. Both commercial and heritage birds responded to a drop in vitamin D3 level by marked reduction in shell thickness. The SDS-PAGE profiles of uterine fluid samples revealed a decrease (P < 0.05) in 200-, 150-, 116-, and ≤6.5-kDa proteins, whereas proteins with molecular weight (MW) of 80, 55, 52, 45, 42, and 28 kDa increased with bird age. A 36- and 52-kDa protein band was most intense for Fayoumi compared with other breeds. Ultrastructural characteristics showed flattened and deeply etched mammillary caps for Lohmann Brown and the presence of type A and type B bodies between mammillary cones in eggshells from Fayoumi and Lohmann Lite. The negative correlation between ultrastructural characteristics, which decrease with bird age, and the 116-kDa uterine protein band could provide insight into reduced eggshell quality as hens age.

Ott's protein osmotic pressure of serum and interstitial fluid in chickens (Gallus gallus): effect of age and gender

Protein, or colloid, osmotic pressure (COP) is of sufficient magnitude to exert a powerful effect on Starling forces across the capillary wall. Although avian skin lacks active mechanisms for fluid transmission, such as sweating, it is now hypothesized that passive oncotic forces may regulate fluid flow and distribution in the skin and related phenomena. In this study, serum protein profiles, as well as COP in serum (COP(s)) and in suction blister fluid (COP(sbf)), were determined in juvenile, young and adult female and male chickens. For assessing COP, the Ott-Ahlqvist equation was applied. This equation can formulate the effects of multiple serum proteins on COP, according to their molecular mass. The COP values determined in chickens were lower than those previously found in mammals. COP(s) increased with age in males, and was higher in adult males than in adult females. In contrast, COP(sbf) decreased with age in females, although it was better preserved in adult males. The age-dependent decrease in COP was associated with a parallel decrease in the concentration of α(1)-globulin and albumin, and a positive correlation between packed cell volume (PCV) and COP was found. It is concluded that ageing affects Ott's COP around the vessel wall, and that an oncotic mechanism preserves plasma volume. The preservation of COP(sbf) in males suggests better maintenance of the interstitial ground substance. Females seem to lose more of a tissue's COP(s) counteracting force than males, probably as a result of gender-specific changes in the composition of the interstitial matrix. Further studies are required to elucidate the structure and function of avian lymphatics and their role in skin rheology.

Histological changes in the uterus of the hens after embryonic exposure to bisphenol A and diethylstilbestrol

Many employed chemicals in industries have estrogenic hormone effects on organisms, and these are called as environmental estrogens. Environmental estrogens have adverse effects on development and function of reproductive organs of the birds. Bisphenol A (BPA) is one of the best known environmental estrogens widely found in plastic products. In this study, we injected BPA and the synthetic estrogen diethylstilbestrol (DES) in ovo and then examined and compared the effects of those on the uteri (shell gland) of the adult hens by histological methods. Five groups have been designed in the current study. Only vehicle substance was given in ovo to the control group and BPA (67 or 134 μg/g egg) and DES (0.02 or 0.2 μg/g egg) were administered in the experimental groups. Tissue specimens were taken from uteri of hens at 21 weeks of age, prior to the laying period. Estrogen receptor alpha (ERα) was immunohistochemically stained. It was observed that the hatching proportion in BPA (67 μg and 134 μg/g) was lesser than the other groups (P<0.01). Uterine tubular glandular density and thickness of tunica mucosa were found to have reduced (P<0.01) in BPA (134 μg/g) and DES (0.2 μg/g) groups, in comparison with those of the control and the other experimental groups. Uterine gland epithelium revealed positive immunoreaction for ERα. These findings suggested that administration of BPA and DES at high doses affected embryonic development in a negative way, and this adverse effect was seen less in adult period.

A mechanistic, stochastic, population model of egg production

1. A mechanistic, stochastic egg production model is presented. Mean age at first egg may be predicted from the lighting programme applied during rearing, using the Bristol-Reading model (Lewis et al., 2002). 2. Rate of ovulation is determined by an amended version of the mathematical model of the ovulatory cycle, originally proposed by Etches and Schoch (1984). 3. Oviposition times are estimated from ovulation times. 4. Yolk, albumen and shell weights are calculated using allometric functions. 5. The model predicts egg production of a theoretical flock of laying hens for a full laying year, including random occurrences of double-yolked and soft-shelled eggs and internal ovulations.

Effect of dietary daidzein on egg production, shell quality, and gene expression of ER-alpha, GH-R, and IGF-IR in shell glands of laying hens

Our previous studies demonstrated that dietary daidzein improves egg production in ducks during the late period of the laying cycle. The present study was aimed to investigate the effect of daidzein in laying hens, with more focus on eggshell quality. The expression of ER-alpha, GH-R, and IGF-IR mRNA in shell glands was determined to identify the target genes of daidzein action and to reveal the relationship between shell quality and profiles of gene expression in shell glands of laying hens. 1000 ISA hens, at 445 days of age, were allotted at random to two groups and given the basal diet with or without 10 mg of daidzein per kg diet for 9 weeks. Daidzein supplement significantly increased the egg laying rate and the feed conversion ratio. The eggshell thickness increased, while the percentage of cracked eggs decreased in daidzein-treated hens. Serum E2 and phosphate concentrations were not altered, but the level of serum Ca2+ and the tibia bone mineral density were significantly increased in the daidzein-treated group compared with their control counterparts. In parallel with the significant increase of oviduct weight, significant down-regulation of GH-R and IGF-IR mRNA and a trend of decrease in ERalpha mRNA expression in shell glands were observed in daidzein-treated hens. The results indicate that dietary daidzein improves egg laying performance and eggshell quality during the late (postpeak) laying stage of hens, which is associated with modulations in gene expression in the shell gland.

Effects of 3-beta-diol, an androgen metabolite with intrinsic estrogen-like effects, in modulating the aquaporin-9 expression in the rat efferent ductules

BACKGROUND

Fluid homeostasis is critical for normal function of the male reproductive tract and aquaporins (AQP) play an important role in maintenance of this water and ion balance. Several AQPs have been identified in the male, but their regulation is not fully comprehended. Hormonal regulation of AQPs appears to be dependent on the steroid in the reproductive tract region. AQP9 displays unique hormonal regulation in the efferent ductules and epididymis, as it is regulated by both estrogen and dihydrotestosterone (DHT) in the efferent ductules, but only by DHT in the initial segment epididymis. Recent data have shown that a metabolite of DHT, 5-alpha-androstane-3-beta-17-beta-diol (3-beta-diol), once considered inactive, is also present in high concentrations in the male and indeed has biological activity. 3-beta-diol does not bind to the androgen receptor, but rather to estrogen receptors ER-alpha and ER-beta, with higher affinity for ER-beta. The existence of this estrogenic DHT metabolite has raised the possibility that estradiol may not be the only estrogen to play a major role in the male reproductive system. Considering that both ER-alpha and ER-beta are highly expressed in efferent ductules, we hypothesized that the DHT regulation of AQP9 could be due to the 3-beta-diol metabolite.

METHODS

To test this hypothesis, adult male rats were submitted to surgical castration followed by estradiol, DHT or 3-beta-diol replacement. Changes in AQP9 expression in the efferent ductules were investigated by using immunohistochemistry and Western blotting assay.

RESULTS

Data show that, after castration, AQP9 expression was significantly reduced in the efferent ductules. 3-beta-diol injections restored AQP9 expression, similar to DHT and estradiol. The results were confirmed by Western blotting assay.

CONCLUSION

This is the first evidence that 3-beta-diol has biological activity in the male reproductive tract and that this androgen metabolite has estrogen-like activity in the efferent ductules, whose major function is the reabsorption of luminal fluid.

The effect of an induced molt and a second cycle of lay on skeletal integrity of White Leghorns

The effect of an induced molt and a second egg laying cycle on White Leghorns hen's skeletal integrity was investigated in a series of 3 experiments. Using dual-energy X-ray absorptiometry, bone mineral density (BMD) and bone mineral content (BMC) of the left tibia and humerus were measured in live hens and excised bones and correlated with invasive bone measurement tests, egg traits, and the incidence of broken bones in carcasses of processed hens. The results of all 3 experiments showed that an induced molt was detrimental to skeletal integrity. For hens that were repeatedly scanned throughout the second cycle of lay, the BMD of the humerus never recovered after the molt. Recovery of tibial BMD to premolt values occurred late in the second cycle of lay when egg production was declining. The in vivo BMD scans conducted between 77 and 117 wk of age correlated with bone breaking force and bone ash weight (r = 0.58 and r = 0.65, respectively; P < 0.0001). The percentage of freshly broken bones per bird at the end of processing at 126 wk of age averaged 34% and ranged from 0 to 61%. The incidence of broken bones was negatively correlated with the excised tibial BMD and BMC at 126 wk of age (r = -0.54 and r = -0.53, respectively; P < 0.05). In conclusion, feed withdrawal for 10 d during an induced molt was detrimental to the skeletal integrity of hens, and as BMD and BMC of excised tibia at 126 wk of age decreased in White Leghorns, the incidence of bone breakage increased.

Western immunoblotting in avian shell gland sample immunoblotting methods

Avian shell gland tissue was subjected to Western blot analysis using anti-human estrogen receptor-alpha antibody H222. Initial attempts to obtain consistent, high-quality blots were unsuccessful because, as it turned out, excessive lipid in tissue preparations interfered with protein separation. Incremental additions of acetone eventually proved to be the critical step in solubilizing lipids and allowing consistent separation of bands on gels. A detailed description of the methodology is presented.

Role of estrogen in avian osteoporosis

One of the difficulties associated with commercial layer production is the development of osteoporosis in hens late in the production cycle. In light of this fact and because of hens' unique requirements for Ca, many studies have focused on the regulation of Ca and the role of estrogen in this process. The time course of estrogen synthesis over the productive life of hens has been well documented; increased circulating estrogen accompanies the onset of sexual maturity while decreases signal a decline in egg production prior to a molt. Numbers of estrogen receptors decrease with age in numerous tissues. The parallel changes in calcium-regulating proteins, primarily Calbindin D28K, and in the ability of duodenal cells to transport Ca, are thought to occur as a result of the changes in estrogen, and are also reversible by the molt process. In addition to the traditional model of estrogen action, evidence now exists for a possible nongenomic action of estrogen via membrane-bound receptors, demonstrated by extremely rapid surges of ionized Ca in chicken granulosa cells in response to 17beta-estradiol. Estrogen receptors have also been discovered in duodenal tissue, and tamoxifen, which binds to the estrogen receptor, has been shown to cause a rapid increase in Ca transport in the duodenum. In addition, recent evidence also suggests that mineralization of bone per se may not explain entirely the etiology of osteoporosis in the hen but that changes in the collagen matrix may contribute through decreases in bone elasticity. Taken together, these studies suggest that changes in estrogen synthesis and estrogen receptor populations may underlie the age-related changes in avian bone. As with postmenopausal women, dietary Ca and vitamin D are of limited benefit as remedies for osteoporosis in the hen.