Rapid alterations of avian medullary bone material during the daily egg-laying cycle

Effects of Clostridium butyricum on Production Performance and Bone Development of Laying Hens

Probiotics are safe, inexpensive, and effective feed additives, and Clostridium butyricum (CB) has been reported to regulate bone health in addition to having conventional probiotic effects. The bone health of laying hens is closely related to their production performance. Here, we investigated the effects of CB supplementation on the bone health and performance of laying hens. We added CB to the feed of green-shell laying hens, Luhua laying hens, and Hy-line Brown laying hens and examined changes in body weight, feed intake, egg production performance, and egg quality to determine the impact of CB on production performance. The impact of CB on the bones of laying hens was determined by analyzing the bone index, bone bending strength, bone calcium and phosphorus content, and bone mineral density. The study found that CB had little effect on the body weight and feed intake of laying hens. Feed additions of 108 and 109 CFU/kg CB can significantly increase the tibia index and bone mineral density of four-week-old green-shell laying hens. Feed additions of 107 and 108 CFU/kg CB can significantly increase the average egg weight, eggshell weight, and tibia index of 26-week-old Luhua laying hens, but 107 CFU/kg CB will reduce the egg production rate. Adding 108 CFU/kg CB to feed can significantly increase the average egg weight, eggshell weight, and tibia bending strength of 40-week-old Hy-line Brown laying hens. In summary, adding 108 CFU/kg CB is beneficial to the bone and production health of laying hens.

Integrated transcriptomic and metabolomic analyses reveal potential regulatory pathways regulating bone metabolism pre- and postsexual maturity in hens

At the onset of sexual maturity, the increasing circulating estrogen stimulates the formation of medullary bone, which provides available calcium for eggshell formation. The bone loss of laying hens is caused by the continuous dynamic changes of structure bone leading to bone fragility and susceptibility. The degree of medullary bone mineralization in sexual maturity is positively correlated with bone quality in the late laying stage. This study aimed to explore the molecular regulation mechanism of bone metabolism pre- and postsexual maturity in hens based on the joint analysis of transcriptome and metabolome. A total of 50 Hy-line Sonia pullets with comparable body weight at 13 wk were selected. Eight pullets were killed at 15 wk (juvenile hens, JH) and 19 wk (laying hens, LH), and LHs were killed within 3 h after oviposition. Differentially expressed genes and metabolites in tibia were analyzed based on transcriptome and metabolome, and then combined to construct the relevant metabolisms and hub genes. In the LH hens, plasma levels of estrogen and tartrate-resistant acid phosphatase were significantly elevated by 1.7 and 1.3 times. In addition, the midpoint diameter, bone mineral density and bone mineral content of the tibia and femur were higher at 19 wk of age. A total of 580 differentially expressed genes were found between the JH and LH group in the tibia, including 280 up-regulated, and 300 down-regulated genes in the LH group. Gene set enrichment analysis (GSEA) showed that the intracellular biosynthesis and secretion of matrix vesicles were significantly enrichment in the LH hens. A total of 21 differential metabolites were identified between JH and LH group. Estradiol valerate positively correlated with L-theanine, tryptophan betaine, dopamine, and perindopril. Joint analysis showed that the top 20 hub genes were enriched in cholesterol biosynthesis and phospholipid metabolism, which played a key regulatory role in bone metabolism during pre- and postsexual maturity. These results provide a theoretical foundation for maintaining efficient egg production and reducing bone health problems in laying hens.

Renal Endocytic Regulation of Vitamin D Metabolism during Maturation and Aging in Laying Hens

Egg-laying hens undergo a specific and dramatic calcium metabolism to lay eggs with eggshells composed of calcium carbonate. Calcium metabolism is mainly regulated by vitamin D3. Although vitamin D3 metabolism is closely related to the deterioration of eggshell quality associated with aging and heat stress, the details of the mechanisms regulating vitamin D3 metabolism are not clear. In mammals, the vitamin D3 metabolite (25(OH)D3) produced in the liver binds to the vitamin binding protein (DBP), is subsequently taken up by renal proximal tubular cells via the endocytic receptors megalin (Meg) and cubilin (CUB), and is metabolized to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Therefore, the present study aimed to examine the expression and localization of Meg and CUB in the kidneys of immature chicks and mature and aged laying hens to prevent eggshell quality deterioration. As a result, we showed that as circulating 1,25(OH)2D3 concentrations increased from 156.0 ± 13.5 pg/mL to 815.5 ± 61.4 pg/mL with maturation in immature chicks, relative expression levels (arbitrary units; AU) of Meg and CUB mRNA in the kidneys of mature hens significantly increased 1.92- and 2.75-fold, respectively, compared to those in immature chicks. On the other hand, the Meg mRNA expression levels of mature hens did not change with age, while CUB mRNA expression levels (1.03 ± 0.11 AU) were significantly decreased compared to mature hens (2.75 ± 0.24 AU). Immunohistochemical observations showed that Meg and CUB proteins were localized to the apical membrane of renal proximal tubular epithelial cells in immature chicks, mature hens, and aged hens, and that DBP protein was observed as granular endosomes in the cytoplasm of proximal tubular cells from the apical membrane to the cell nucleus. Especially in mature hens, the endosomes were larger and more numerous than those in immature chicks. In contrast, in aged hens, DBP-containing endosomes were smaller and limited to the apical cytoplasm. These results indicate that with maturation, the expression of Meg and CUB is promoted in the renal proximal tubules of laying hens, facilitating the uptake of the 25(OH)D3-DBP complex and its conversion to 1,25(OH)2D3, and regulating calcium metabolism in eggshell formation. On the other hand, it is suggested that the age-related decrease in CUB expression suppresses the uptake of the 25(OH)D3-DBP complex in the kidney, resulting in a deterioration of eggshell quality.

Body composition, gastrointestinal, and reproductive differences between broiler breeders fed using everyday or skip-a-day rearing programs

Broiler breeder feed restriction practices have intensified as broiler feed efficiency has been improved. Skip-a-day (SAD) rearing regimen has controlled breeder growth, although this practice has become questionable for the modern breeder. We compared everyday (ED) and SAD programs and evaluated their impact on pullet growth performance, body composition, gastrointestinal tract development, and reproduction. At d 0, Ross 708 (Aviagen) pullet chicks (n = 1,778) were randomly assigned to 7 floor pens. Three pens were fed using the ED and 4 pens with SAD program through wk 21 using a chain-feeder system. ED and SAD grower diets were formulated to be isonutritious, with the only difference that ED diets had more crude fiber. Pullets (n = 44 per pen) were moved to 16 hen pens by treatment at wk 21 with 3 YP males (Aviagen) in each pen. All birds were fed common laying diets. In addition to BW data, sampled pullets and hens were scanned using dual energy X-ray absorptiometry (DEXA) to obtain body bone density and composition. Hen performance and hatchery metrics were recorded through wk 60. ED birds were heavier with similar nutrient intake from wk 10 to 45 (P ≤ 0.013). Pullet uniformity was unaffected by feeding method (P ≥ 0.443). SAD pullets had less body fat at wk 19 (P = 0.034) compared to ED pullets, likely as a metabolic consequence of intermittent feeding. SAD birds had lower bone density at wk 7, 15, and 19 (P ≤ 0.026). At 4 wk of age, SAD pullets had less intestinal villi goblet cells compared to ED pullets (P ≤ 0.050), possibly explained by the effect that feed removal has on cell migration rates. Overall egg-specific gravity (P = 0.057) and hatch of fertile % (P = 0.088) tended to be higher in eggs from ED hens. Altogether, ED feeding increased young pullet intestinal goblet cells and increased both bone density and body fat at wk 19. ED program improved pullet feed conversion (2.6% less feed) and increased eggshell quality and hatch of fertile.

Palaeoecological deductions from osteohistology

Palaeoecological deductions are vital for understanding the evolution and diversification of species within prehistoric environments. This review highlights the multitude of ways in which the microanatomy and microscopic structure of bones enables palaeoecological deductions. The occurrence of growth marks in bones is discussed, and their usefulness in deducing the ontogenetic status and age of individuals is considered, as well as how such marks in bones permit the assessment of the growth dynamics of individuals and species. Here osteohistology is shown to provide insight into the structure of past populations, as well as ecological relationships between individuals. In addition, the response of bones to trauma, disease and moulting is considered. Finally, I explore how osteohistology can give insight into ecomorphological adaptations, such as filter feeding, probe feeding and saltatorial locomotion. Methodological advances in three-dimensional microtomography and synchrotron scanning bodes well for future studies in osteohistology and despite some compromises in terms of tissue identity, circumvents the crucial issue of destructive analyses.

Physicochemical Characterization of Thermally Processed Goose Bone Ash for Bone Regeneration

Goose bone is traditionally applied for many ailments including bone fractures. Goose bone that consists of calcium phosphate plays a major role in bone regeneration. In this study, the production of goose bone ash (GBA) was translated from a traditional process into one of a laboratory scale via thermal and mechanical methods. The GBA was thermally processed via calcination at 300 °C and 900 °C. The differences in physicochemical properties between studied GBA (SGBA) and commercial GBA (CGBA) were elucidated via Fourier transform infrared (FT-IR), X-ray fluorescence (XRF), X-ray diffraction (XRD) and electron diffraction X-Ray (EDX). The morphological properties of SGBA and CGBA were characterized using field emission scanning electron microscopy (FESEM) in which nano-sized particles were detected. The results showed that the SGBA of 300 °C had comparable physicochemical properties to those of CGBA. A high processing temperature was associated with decreasing organic compounds and increasing crystallinity. The finding from EDX suggests that sintering at 900 °C (SGBA 900) demonstrated the presence of hydroxyapatite in the mineralogical phase and had a Ca/P atomic ratio of 1.64 which is comparable to the ideal stoichiometric ratio of 1.67. Findings from this study could be used for the further exploration of GBA as a potential material for bone regeneration via the elucidation of their biological properties in the next experimental setting.

Genetic markers associated with bone composition in Rhode Island Red laying hens

BACKGROUND

Bone damage has welfare and economic impacts on modern commercial poultry and is known as one of the major challenges in the poultry industry. Bone damage is particularly common in laying hens and is probably due to the physiological link between bone and the egg laying process. Previous studies identified and validated quantitative trait loci (QTL) for bone strength in White Leghorn laying hens based on several measurements, including bone composition measurements on the cortex and medulla of the tibia bone. In a previous pedigree-based analysis, bone composition measurements showed heritabilities ranging from 0.18 to 0.41 and moderate to strong genetic correlations with tibia strength and density. Bone composition was measured using infrared spectroscopy and thermogravimetry. The aim of this study was to combine these bone composition measurements with genotyping data via a genome-wide association study (GWAS) to investigate genetic markers that contribute to genetic variance in bone composition in Rhode Island Red laying hens. In addition, we investigated the genetic correlations between bone composition and bone strength.

RESULTS

We found novel genetic markers that are significantly associated with cortical lipid, cortical mineral scattering, medullary organic matter, and medullary mineralization. Composition of the bone organic matter showed more significant associations than bone mineral composition. We also found interesting overlaps between the GWAS results for tibia composition traits, particularly for cortical lipid and tibia strength. Bone composition measurements by infrared spectroscopy showed more significant associations than thermogravimetry measurements. Based on the results of infrared spectroscopy, cortical lipid showed the highest genetic correlations with tibia density, which was negative (- 0.20 ± 0.04), followed by cortical CO3/PO4 (0.18 ± 0.04). Based on the results of thermogravimetry, medullary organic matter% and mineral% showed the highest genetic correlations with tibia density (- 0.25 ± 0.04 and 0.25 ± 0.04, respectively).

CONCLUSIONS

This study detected novel genetic associations for bone composition traits, particularly those involving organic matter, that could be used as a basis for further molecular genetic investigations. Tibia cortical lipids displayed the strongest genetic associations of all the composition measurements, including a significantly high genetic correlation with tibia density and strength. Our results also highlighted that cortical lipid may be a key measurement for further avian bone studies.

The effects of myostatin mutation on the tibia bone quality in female Japanese quail before and after sexual maturation

In the modern layer industry, improvement of bone quality is one of the prior tasks to solve from economic and welfare standpoints. In addition to nutritional and environmental factors, genetic factors have been considered major factors regulating bone quality in layers but are yet to be fully investigated due to limitations on available animal models. Initially, the myostatin (MSTN) gene was genetically edited in quail to investigate the effect of MSTN mutation on economic traits in meat producing poultry species. In the current study, the function of the MSTN gene on regulation of bone quality in layers was investigated using MSTN mutant female quail as an animal model. Tibia bones were collected from wild-type (WT) and MSTN mutant female quail at 5 wk old and 4 mo old, representing prelaying and actively laying stages, respectively. Left tibia bones were analyzed by microcomputed tomography scanning to evaluate the architectural characteristics, while bone breaking strength (BBS) was measured using right tibia bones. At 5 wk of age, MSTN mutant female quail showed higher BBS and values on parameters related to bone quality such as bone mineral contents (BMC), bone mineral density (BMD), bone volume (BV), and/or trabecular bone thickness in whole diaphysis, whole metaphysis, and metaphyseal trabecular bone, compared to WT female quail. Although BBS and BMD became similar between the 2 groups at 4 mo of age, higher TV and TS in whole metaphysis and higher BMC and TV in whole diaphysis of MSTN mutant group compared to those of WT group suggested that the improved tibia bone quality by MSTN mutation before sexual maturation lasted to a certain degree even after sexual maturation. The use of the MSTN mutant female model provided new insights into genetic regulation on female quail bone quality depending on physiological changes.

Effects of Low-Phosphorus Diets Supplemented with Phytase on the Production Performance, Phosphorus-Calcium Metabolism, and Bone Metabolism of Aged Hy-Line Brown Laying Hens

This study was conducted to evaluate the effects of phytase supplementation in low-phosphorus diets on the production performance, phosphorus–calcium metabolism, and bone metabolism in laying hens from 69 to 78 weeks of age. Hy-Line Brown laying hens (n = 1350) were assigned randomly to six treatments with five replicates of 45 birds. A corn–soybean meal-based diet with no inorganic phosphates was formulated to contain 0.12% non-phytate phosphorus (NPP) and 1470 FTU/kg phytase (Released phytate phosphorus content ≥ 0.1%). Inorganic phosphorus (dicalcium phosphate) was supplemented into the basal diet to construct five test diets (level of NPP supplementation = 0.10%, 0.15%, 0.20%, 0.25%, and 0.30%). The level of calcium carbonate was adjusted to ensure that all six experimental diets contained the same calcium percentage (3.81%). The feeding trial lasted 10 weeks (hens from 69 to 78 weeks of age). Upon supplementation with phytase (1470 FTU/kg), supplemental inorganic phosphates (dicalcium phosphate) had no significant effects (p > 0.05) on the production performance or egg quality. Significant differences in serum levels of calcium, phosphorus, copper, iron, zinc, or manganese were not detected across treatments (p > 0.05). Hens fed NPP (0.15%, 0.20%, 0.25%, and 0.30%) had higher levels (p < 0.0001) of tibial ash, calcium, and phosphorus than those not fed inorganic phosphates. The tibial breaking strength of the group without inorganic phosphates was significantly lower than that of the other groups (p < 0.01). Dietary supplementation with inorganic phosphates had no effect (p > 0.05) on serum levels of calcitonin (CT) and 1,25-dihydroxy-vitamin D3 (1,25-(OH)2D3). Hens that did not receive supplementation with inorganic phosphates had higher serum levels of parathyroid hormone (PTH), osteoprotegerin (OPG), type-I collagen c-telopeptide (CTX-I), and tartrate-resistant acid phosphatase 5b (TRACP-5b) compared with those in the other groups (p < 0.01). Serum levels of CTX-I and TRACP-5b were significantly lower in the NPP-supplementation groups of 0.25% and 0.30% than in the 0.10% NPP-supplementation group (p < 0.01). Dietary supplementation with inorganic phosphates had no effect (p > 0.05) on serum levels of bone-alkaline phosphatase (BAP), osteocalcin (OCN), or osteopontin (OPN). Hens not fed inorganic phosphate had the highest renal expression of phosphorus transporter type IIa Na/Pi cotransporter (NaPi-Ⅱa). Renal expression of NaPi-Ⅱa was increased significantly in NPP-supplementation groups of 0.10–0.20% compared with that in NPP-supplementation groups of 0.25% and 0.30% (p < 0.0001). The results indicated that a reduction in NPP supplementation to 0.15% (dietary NPP level = 0.27%) with phytase inclusion did not have an adverse effect on the production performance or bone health of laying hens from 69 to 78 weeks of age, which might be attributed to renal phosphorus reabsorption and bone resorption. These findings could support the application of low-phosphorus diets in the poultry industry.

Adjusting phosphate feeding regimen according to daily rhythm increases eggshell quality via enhancing medullary bone remodeling in laying hens

BACKGROUND

Body phosphorus metabolism exhibits a circadian rhythm over the 24-h daily cycle. The egg laying behavior makes laying hens a very special model for investigating phosphorus circadian rhythms. There is lack of information about the impact of adjusting phosphate feeding regimen according to daily rhythm on the phosphorus homeostasis and bone remodeling of laying hens.

METHODS AND RESULTS

Two experiments were conducted. In Exp. 1, Hy-Line Brown laying hens (n = 45) were sampled according the oviposition cycle (at 0, 6, 12, and 18 h post-oviposition, and at the next oviposition, respectively; n = 9 at each time point). Diurnal rhythms of body calcium/phosphorus ingestions and excretions, serum calcium/phosphorus levels, oviduct uterus calcium transporter expressions, and medullary bone (MB) remodeling were illustrated. In Exp. 2, two diets with different phosphorus levels (0.32% and 0.14% non-phytate phosphorus (NPP), respectively) were alternately presented to the laying hens. Briefly, four phosphorus feeding regimens in total (each included 6 replicates of 5 hens): (1) fed 0.32% NPP at both 09:00 and 17:00; (2) fed 0.32% NPP at 09:00 and 0.14% NPP at 17:00; (3) fed 0.14% NPP at 09:00 and 0.32% NPP at 17:00; (4) fed 0.14% NPP at both 09:00 and 17:00. As a result, the regimen fed 0.14% NPP at 09:00 and 0.32% NPP at 17:00, which was designed to strengthen intrinsic phosphate circadian rhythms according to the findings in Exp. 1, enhanced (P < 0.05) MB remodeling (indicated by histological images, serum markers and bone mineralization gene expressions), elevated (P < 0.05) oviduct uterus calcium transportation (indicated by transient receptor potential vanilloid 6 protein expression), and subsequently increased (P < 0.05) eggshell thickness, eggshell strength, egg specific gravity and eggshell index in laying hens.

CONCLUSIONS

These results underscore the importance of manipulating the sequence of daily phosphorus ingestion, instead of simply controlling dietary phosphate concentrations, in modifying the bone remodeling process. Body phosphorus rhythms will need to be maintained during the daily eggshell calcification cycle.

Physiological regulation of calcium and phosphorus utilization in laying hens

Commercial laying hens can produce one egg approximately every 24 h. During this process, regulatory systems that control vitamin D₃ metabolism, calcium and phosphorus homeostasis, and intestinal uptake of these minerals work in concert to deliver components required for eggshell calcification and bone mineralization. Commercial production cycles have been extended in recent years to last through 100 weeks of age, and older hens often exhibit an increased prevalence of skeletal fractures and poor eggshell quality. Issues such as these arise, in part, through imbalances that occur in calcium and phosphorus utilization as hens age. As a result, an in-depth understanding of the mechanisms that drive calcium and phosphorus uptake and utilization is required to develop solutions to these welfare and economic challenges. This paper reviews factors that influence calcium and phosphorus homeostasis in laying hens, including eggshell formation and development and roles of cortical and medullary bone. Metabolism and actions of vitamin D₃ and physiological regulation of calcium and phosphorus homeostasis in key tissues are also discussed. Areas that require further research in avian species, such as the role of fibroblast growth factor 23 in these processes and the metabolism and action of bioactive vitamin D₃, are highlighted and the importance of using emerging technologies and establishing in vitro systems to perform functional and mechanistic studies is emphasized.

Effect of strontium ranelate and cerium oxide addition in the diet on egg production and eggshell quality in laying hen

Minerals are used widely as feed additives in the diets of poultry to enhance bone and egg quality and productivity. Therefore, the current study aimed to evaluate the impact of strontium ranelate and cerium oxide addition in the diet on egg production and eggshell quality in laying hens. In this experiment, a total of 240 laying hens at the age of 44 weeks old, were divided into six treatments, with four replicates per treatment (10 hens per replicate). The hens were fed a standard diet for five weeks as an introductory period of preparation. The design of the dietary treatments was formulated as: control (T1) basal diet, Strontium ranelate (SrR) 400 and 800 mg/kg in basal diet (T2 and T3), Cerium oxide (CeO) 250 and 500 mg/kg in basal diet (T4 and T5) and their combination 400 mg/kg of Strontium ranelate + 250 mg/kg of Cerium oxide (T6) in the basal diet. Laying hen’s performance and, egg quality (eggshell strength, eggshell thickness, eggshell percentage, minerals in eggshell, yolk index and Haugh unit), were analyzed. The results showed that the addition of SrR and CeO did not affect performance, yolk index, Haugh unit, ratio of Ca, P, and Ce in the eggshell. However, supplementing 800 mg/kg SrR significantly increased eggshell strength, thickness, percentage, Sr in the eggshell compared to the control, while supplementing 250 or 500 mg/kg CeO significantly increased eggshell strength and thickness. The combination of SrR and CeO significantly increased eggshell strength compared to the control group. In conclusion, supplementing SrR (800 mg/kg) and CeO significantly improved the quality of the eggshell.

Transcriptomic analysis reveals the molecular mechanisms underlying osteoclast differentiation in the estrogen-deficient pullets

Several previous reports have suggested that estrogen (E2) is a vital signal responsible for the regulation of skeletal homeostasis and bone remodeling in mammals. E2 could efficiently accelerate the growth of medullary bone in pullets during sexual maturity. Furthermore, the low E2 level can strengthen the mechanical bone functions in female hens. However, mechanistic studies to describe the effects of E2 on bone in pullets during the initiation of the puberty period are remaining elusive. Therefore, the aim of this study was to explore the effect of inhibiting E2 biosynthesis on the biomechanical properties and its molecular mechanism during sexual maturity of pullets. In this study, a total of 90 Hy-line Sonia pullets with comparable body weight at 13 wk of age were selected and categorized into 2 separate groups. Daily, 0.5 mg/4 mL of letrozole (LZ) was orally administered to the treatment (TRT) group and 4 mL of saline to the control (CON) group of pullets for 6 wk. Compared with the CON group, a lower plasma E2 level was observed in the TRT group. Furthermore, plasma P, Gla protein (BGP), and 1,25-dihydroxy vitamin D3 (1,25-(OH)₂D₃) levels were markedly suppressed, whereas the plasma alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) levels were significantly elevated. Moreover, the cortical bone thickness and breaking strength of the tibia and femur, the bone mineral density of the humerus, and the bone mineral content of the humerus as well as the femur were increased significantly. The expression levels of 340 differentially expressed genes (DEGs) differed significantly between the CON and TRT group in the tibia at 19 wk of age. Among them, 32 genes were up-regulated, whereas 308 were down-regulated in the TRT group. The variations in candidate genes associated with osteoclast differentiation and cell adhesion may indicate that LZ inhibits E2 biosynthesis, consequently, reduces osteoclast differentiation by suppressing inter-cellular communication and cells attaching to extracellular matrix components. Taken together, the present study demonstrated that inhibiting E2 synthesis during sexual maturity of pullets decreased osteoclast differentiation and considerably enhanced bone quality.

Assessing Bone Health Status and Eggshell Quality of Laying Hens at the End of a Production Cycle in Response to Inclusion of a Hybrid Rye to a Wheat-Corn Diet

The objective of this study was to evaluate whether there are negative effects of the partial replacement of white corn with rye along with xylanase supplementation on overall bone quality, eggshell mineralization, and mechanical strength in laying hens. From the 26th week of life, ISA Brown laying hens were fed either a wheat-corn diet or a diet containing 25% rye, with or without xylanase. The experimental period lasted for 25 weeks, until birds reached their 50th week of age, after which bone and eggshell quality indices were assessed. Eggshell thickness and eggshell Ca content of eggs from rye-fed hens were improved by xylanase supplementation. No differences in the mechanical properties of the eggshells were observed between treatments, except for the diet-dependent changes in egg deformation. Rye inclusion had no effect on the mechanical properties of bone. Xylanase supplementation, irrespective of the diet, had a positive effect on bone strength and increased tibia Ca content, as well as the content of several microelements. Hence, hybrid rye combined with wheat can replace 25% of corn in layer diets without compromising shell quality or bone mineral content. Xylanase supplementation in these diets is recommended since its inclusion improves both bone strength and quality.

Fibroblast growth factor 23 inhibits osteogenic differentiation and mineralization of chicken bone marrow mesenchymal stem cells

Fibroblast growth factor 23 (FGF23), a bone-derived hormone, is involved in the reabsorption of phosphate (P) and the production of vitamin D hormones in the kidney. However, whether and how FGF23 regulates chicken bone metabolism remains largely unknown. In the present study, we investigated the effect of FGF23 on osteogenic differentiation and mineralization of chicken bone marrow mesenchymal stem cells (BMSCs). First, we found that the transcription of FGF23 was inhibited by β-glycerophosphate sodium (GPS, 5 mM, 10 mM, 20 mM) and 10^-9 M 1, 25-dihydroxyvitamin D3 (1, 25(OH)₂D₃), but was stimulated by 10^-7 M 1, 25(OH)₂D₃ and parathyroid hormone (PTH, 10^-9 M, 10^-8 M, 10^-7 M). Second, overexpression of FGF23 by the FGF23 adenovirus (Adv-FGF23) suppressed the formation of mineralized nodules (P < 0.001) and alkaline phosphatase (ALP) activity (P < 0.05) in both differentiated and mineralized osteoblasts. Administration of FGF receptor 3 (FGFR3) inhibitor (50 nM) was sufficient to restore the FGF23-decreased ALP activity (P < 0.05), but not for the formation of mineralized nodules. In addition, the phosphorylation of ERK increased considerably with Adv-FGF23 overexpression (P < 0.05). Administration of an ERK-specific inhibitor (10 μM) could down-regulate the phosphorylation of ERK (P-ERK) (P < 0.05) and slightly restored the Adv-FGF23-reduction of ALP activity (P = 0.08). In summary, our data suggest that GPS, 1, 25(OH)₂D₃, and PTH could regulate FGF23 mRNA expression in vitro. FGF23 is a negative regulator of bone remodeling. FGF23 not only inhibits BMSCs osteogenesis through the FGFR3-ERK signaling pathway but also suppresses the mineralization of mature osteoblasts.

Productive performance, perching behavior, keel bone and other health aspects in dual-purpose compared to conventional laying hens

Several alternatives to avoid killing male day-old chicks are available. One of these alternatives is to keep dual-purpose chicken strains. The aim of this study was to compare dual-purpose hens (Lohmann Dual, LD) with conventional laying hens (Lohmann Tradition, LT) in terms of performance, animal welfare parameters such as keel bone state and foot pad dermatitis, and perching behavior. We expected a generally equal or even better performance of the dual-purpose hens except for laying performance. Four hundred female day-old chicks were housed in 6 pens (3 pens per strain) and reared until 54 wk of age. Each pen offered a littered area, elevated slatted manure pit, elevated wooden frame with perches or grids and nest boxes on the manure pit. The wooden frame was alternately equipped with perches or grids. The elevated manure pit as well as the elevated structure was accessible via ramp. Productive performance parameters like mortality, total number of eggs and body weight were assessed periodically. In week 49, 132 hens (66 hens per strain) were randomly selected for radiography of the keel bone and assessment of plumage and foot pad state. Perching behavior was analyzed via scan sampling during rearing and laying period, respectively. Statistical analyzes were done with Linear Mixed Effect Model and General Linear Mixed Model. LD had a higher radiographic density than LT hens (P = 0.0016), other keel bone parameters (fracture score, P = 0.36; deformation, P = 0.83) showed no differences. The vast majority of fractures occurring in both strains were located in the caudal part of the keel bone. During the laying period, usage of elevated structures was higher with grids compared to perches (P < 0.001) and in LD compared to LT (P = 0.01). Some animal welfare problems were less frequent in LD compared to LT hens while other problems did not differ between the 2 strains or were even more frequent in LD hens. Grids may be more suitable as resting area than perches and may possibly help to decrease the prevalence of keel bone damage.

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.

A simple daily dynamic feeding regimen for reducing phosphorus consumption and excretion in laying hens

Phosphorus metabolism in laying hens is a highly dynamic process over the course of the 24 h egg-laying cycle. Adjusting the phosphorus feeding regimen according to the daily egg-laying cycle may help to improve phosphorus utilization efficiency. Hy-Line Brown layers (n = 120; 70 wk old) were offered 4 different phosphorus daily regimens: (1) RR, fed regular phosphorus at both 09:00 and 17:00; (2) RL, fed regular phosphorus at 09:00 and low phosphorus at 17:00; (3) LR, fed low phosphorus at 09:00 and regular phosphorus at 17:00; (4) LL, fed low phosphorus at both 09:00 and 17:00. The regular and low phosphorus diets contained 0.32% and 0.14% non-phytate phosphorus, respectively. The feeding trial lasted for 12 wk. As a result, layers on the RL regimen had decreased laying rate (P < 0.05; 5 to 8, 9 to 12, and 1 to 12 wk) when compared to all other regimens. Layers on the LL regimen had decreased eggshell thickness and specific gravity (P < 0.05; wk 8) when compared to all other regimens, and had decreased egg shell strength (P < 0.05; wk 8) when compared to RL and LR regimens. When compared to the RR regimen (a common practice in the industry), layers on the LR regimen had: (1) identical laying performance and egg quality (P > 0.05); (2) decreased phosphorus excretion (P < 0.05) during the period of 09:00 to 17:00; (3) increased jejunal calbindin D28k protein expression (P < 0.05) 2 h after feeding in the morning; (4) decreased serum fibroblast growth factor 23 and calcitriol levels (P < 0.05), decreased jejunal type III sodium-phosphate cotransporter 2 gene and protein expression (P < 0.05), and decreased renal type III sodium-phosphate cotransporter 1 protein expression (P < 0.05), 2 h after feeding in the afternoon. In summary, when dietary phosphorus was supplemented in accordance with daily serum phosphorus rhythms (i.e., the LR regimen), laying performance and egg quality were well supported whilst significantly decreasing phosphorus consumption and excretion. Thus, serum phosphorus rhythms will need to be carefully maintained when developing dietary phosphorus-reduction strategies in laying hens.

Dietary vitamin D3 deprivation suppresses fibroblast growth factor 23 signals by reducing serum phosphorus levels in laying hens

The present study was carried out to evaluate the effect of dietary supplemental vitamin D₃ on fibroblast growth factor 23 (FGF23) signals as well as phosphorus homeostasis and metabolism in laying hens. Fourteen 40-week-old Hy-Line Brown layers were randomly assigned into 2 treatments: 1) vitamin D₃ restriction group (n = 7) fed 0 IU/kg vitamin D₃ diet, and 2) regular vitamin D₃ group (n = 7) fed 1,600 IU/kg vitamin D₃ diet. The study lasted for 21 d. Serum parameters, phosphorus and calcium excretion status, and tissue expressions of type II sodium-phosphate co-transporters (NPt2), FGF23 signals and vitamin D₃ metabolic regulators were determined. Hens fed the vitamin D₃ restricted diet had decreased serum phosphorus levels (by 31.3%, P = 0.028) when compared to those fed regular vitamin D₃ diet. In response to the decreased serum phosphorus, the vitamin D₃ restricted laying hens exhibited: 1) suppressed kidney expressions of 25-hydroxyvitamin D 1-α-hydroxylase (CYP27B1, by 52.8%, P = 0.036) and 1,25-dihydroxyvitamin D 24-hydroxylase (CYP24A1, by 99.4%, P = 0.032); 2) suppressed serum levels of FGF23 (by 14.6%, P = 0.048) and increased serum alkaline phosphatase level (by 414.1%, P = 0.012); 3) decreased calvaria mRNA expressions of fibroblast growth factor receptors (FGFR1, by 85.2%, P = 0.003, FGFR2, by 89.4%, P = 0.014, FGFR3, by 88.8%, P = 0.017, FGFR4, by 89.6%, P = 0.030); 4) decreased kidney mRNA expressions of FGFR1 (by 65.5%, P = 0.021), FGFR4 (by 66.0%, P = 0.050) and KLOTHO (by 68.8%, P = 0.038); 5) decreased kidney protein expression of type 2a sodium-phosphorus co-transporters (by 54.3%, P = 0.039); and 6) increased percent excreta calcium (by 26.9%, P = 0.002). In conclusion, the deprivation of dietary vitamin D₃ decreased FGF23 signals in laying hens by reducing serum FGF23 level and suppressing calvaria and kidney mRNA expressions of FGF23 receptors.

Genetic Parameter Estimation and Whole Sequencing Analysis of the Genetic Architecture of Chicken Keel Bending

Bone health is particularly important for high-yielding commercial layer chickens. The keel of poultry is an extension of the abdomen side of the sternum along the sagittal plane and is one of the most important bones. In this study, the keel phenotype of White Leghorns laying hen flocks showed significant individual differences. To clarify its genetic mechanism, we first estimated the heritability of keel bend (KB) in White Leghorn, recorded the production performance of the chicken flock, examined the blood biochemical indexes and bone quality in KB and keel normal (KN) chickens, and performed whole-genome pooled sequencing in KB and KN chickens. We then performed selection elimination analysis to determine the genomic regions that may affect the keel phenotypes. The results show that KB is a medium heritability trait. We found that cage height had a significant effect on the KB (p < 0.01). At 48 weeks, there were significant differences in the number of eggs, the number of normal eggs, and eggshell strength (p < 0.05). The content of parathyroid hormone was lower (p < 0.01) and that of calcitonin was higher (p < 0.01) in KB chickens than in KN chickens. The differences in bone mineral density, bone strength, and bone cortical thickness of the humerus and femur were extremely significant (p < 0.01), with all being lower in KB chickens than in KN chickens. In addition, the bones of KB chickens contained more fat organization. A total of 128 genes were identified in selective sweep regions. We identified 10 important candidate genes: ACP5, WNT1, NFIX, CNN1, CALR, FKBP11, TRAPPC5, MAP2K7, RELA, and ENSGALG00000047166. Among the significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways found, we identifed two bone-related pathways, one involving “osteoclast differentiation” and the other the “MAPK signaling pathway.” These results may help us better understand the molecular mechanism of bone traits in chickens and other birds and provide new insights for the genetic breeding of chickens.

Bone and eggshell quality throughout an extended laying cycle in three strains of layers spanning 50 years of selection

Decades of intensive genetic selection in commercial layers has resulted in earlier maturation, while sustaining high production rates to 100 wks of age (woa). To support eggshell formation while maintaining a healthy skeletal frame, substantial adaptations of calcium metabolism in the hen are necessary. Thus, skeletal growth, bone density, and egg quality were compared in 3 strains of layers, with the Lohmann LSL-lite as the current commercial strain, the heritage Shaver white leghorn as the mid-2000s strain, and the white-leghorn derived Smoky Joes as the non-selected 1960s strain. Tibia and Femur (n = 4/strain) were collected at 12, 17, 20, 25, 45, 60, 75, and 100 woa. Bones were measured and weighed, with bone mineral density assessed within medullary (mBMD) and cortical (cBMD) regions of the tibia using micro-Computed Tomography. Egg analyses including weight, eggshell thickness (EST) and eggshell breaking strength (EBS), were conducted throughout lay. Blood samples were collected to measure plasma calcium immediately prior to lay (18 woa) and periodically throughout the laying cycle. Femur and tibia weight, or size, did not increase beyond 12 woa, indicating that all hens reached maximum skeletal size by this time. An interaction (P = 0.005) was observed between strain and tibia mBMD, as all three strains demonstrated an accumulation of medullary bone from 12 to 100 woa. Regarding egg weight, while Lohmann hen eggs displayed the highest quality at 26 woa, an elevation in egg weight in Lohmann and Shaver hens (P < 0.001) resulted in a decline in EST and EBS over time (P < 0.01). Yet, at 100 woa, no strain differed in EST or EBS, despite larger variations in cumulative egg numbers (P < 0.001). Plasma calcium levels were significantly elevated between the immature state and peak of lay but remained unchanged throughout lay in all strains. In conclusion, our results show that although genetic selection of layer hens resulted in tremendous improvement in productivity, no detrimental effects on cBMD or mBMD were observed throughout an extended laying period up to 100 woa.

Medullary bone in male budgerigars (Melopsittacus undulatus) with testicular neoplasms

Medullary bone is a calcium-rich, labile bone normally occurring in female birds with each egg-laying cycle. The stimulus for formation of medullary bone is, in part, the cyclic increase in serum estrogens produced by preovulatory ovarian follicles. Increased bone density due to formation of medullary bone, particularly in pneumatic bones, has been termed polyostotic hyperostosis, even if physiologic. This study investigated the formation of medullary bone in nonpneumatic (femur) and pneumatic (humerus) bones in sexually mature male budgerigars submitted for autopsy. Of the 21 sexually mature male budgerigars submitted for autopsy, 7 (33%) had medullary bone in 1 or more bones examined. All 7 male budgerigars with medullary bone had a testicular neoplasm, which was morphologically consistent with a testicular sustentacular cell tumor, seminoma, or interstitial cell tumor. Medullary bone was not present in the 14 cases with other diseases. Medullary bone formation in pneumatic and nonpneumatic bones can occur in male budgerigars with testicular neoplasms. Radiographic increases in medullary bone density, particularly in the humerus, could provide antemortem indication of testicular neoplasia in male budgerigars.

Dietary zinc supplementation affects eggshell quality and ultrastructure in commercial laying ducks by influencing calcium metabolism

This study evaluated dietary Zn supplementation on productive performance, eggshell quality and ultrastructure, and calcium metabolism during eggshell formation in laying ducks. A total of 360 Longyan laying ducks (45-wk) were randomly divided into 5 treatment groups with 6 replicates of 12 birds each and fed for 20 wk. The 6 treatments fed the basal diet supplemented with 0 (control), 20, 40, 80, or 160 mg Zn/kg (ZnSO4·H2O). Dietary supplemental level at 80 mg/kg increased egg production (4.3%) and mass (5.7%), and decreased FCR (2.9%) compared to the basal diet, and these indices increased quadratically with increasing Zn supplemental levels (P < 0.05). The shell breaking strength (15.8%) and fracture toughness (10.6%) were higher with the supplementation of Zn at 80 mg/kg than the basal diet, and increased quadratically with Zn supplementation (P < 0.05). Dietary supplementation of Zn at 80 mg/kg improved shell ultrastructure by increasing total (9.0%) and effective thickness (14.2%) and decreasing mammillary thickness (12.0%), and their responses were quadratic with increasing Zn levels (P < 0.05). The supplementation of Zn affected the calcium contents in plasma, tibias and ulna, ulna phosphorus content, and linear and quadratic effects were observed, and higher values were observed with 160 mg/kg Zn supplementation than control (P < 0.05). The supplemental Zn level at 80 mg/kg increased shell effective thickness in growth stage (P < 0.05), and shell calcium and phosphorus content in initial and growth stages (P < 0.05). Dietary Zn supplementation did not affect the gene expression of Ca2+ transporters in the eggshell gland, but affected the expression of HCO3- exchanger in initial and growth stage (P < 0.05). Overall, dietary Zn supplementation could improve productive performance and shell quality in laying ducks at late phase of production, and calcium metabolism and deposition were modulated by Zn influencing HCO3- secretion and thus affecting shell ultrastructure and quality. A supplemental level of 80 mg/kg Zn in the diet with a basal content of 34.0 mg/kg was optimal, and higher level (160 mg/kg) decreased shell calcium deposition by depressing its metabolism.

Regional femoral bone blood flow rates in laying and non-laying chickens estimated with fluorescent microspheres

The metabolic rate of vertebrate bone tissue is related to bone growth, repair and homeostasis, which are all dependent on life stage. Bone metabolic rate is difficult to measure directly, but absolute blood flow rate () should reflect local tissue oxygen requirements. A recent ‘foramen technique’ has derived an index of blood flow rate () by measuring nutrient foramen sizes of long bones. is assumed to be proportional to ; however, the assumption has never been tested. This study used fluorescent microsphere infusion to measure femoral bone in anaesthetized non-laying hens, laying hens and roosters. Mean mass-specific cardiac output was 338±38 ml min⁻¹ kg⁻¹, and the two femora received 0.63±0.10% of this. Laying hens had higher wet bone mass-specific to femora (0.23±0.09 ml min⁻¹ g⁻¹) than the non-laying hens (0.12±0.06 ml min⁻¹ g⁻¹) and roosters (0.14±0.04 ml min⁻¹ g⁻¹), presumably associated with higher bone calcium mobilization during eggshell production. Estimated metabolic rate of femoral bone was 0.019 ml O₂ min⁻¹ g⁻¹. Femoral increased significantly with body mass, but was not correlated with nutrient foramen radius (r), probably because of a narrow range in foramen radius. Over all 18 chickens, femoral shaft was 1.07±0.30 ml min⁻¹ mm⁻¹. Mean in chickens was significantly higher than predicted by an allometric relationship for adult cursorial bird species, possibly because the birds were still growing.

Summary: Femoral bone blood flow, measured using fluorescent microspheres, is approximately two times higher in laying hens than in non-laying hens and roosters. Blood flow values were related to foramen sizes.

Comparative analysis of the morphology, chemistry and structure of the tibiotarsus, humerus and keel bones in laying hens

1. Bone properties are adapted to their specific functions in the animal, so various types of bones develop different characteristics depending on their location in the skeleton.2. The aim of this research was to compare the chemical composition, mineral characteristics and structural organisation in tibiotarsus, humerus and keel bones as representatives of hen skeletal mineralisation. Complementary analytical techniques, such as X-ray radiography, optical and electron microscopy, thermogravimetry and 2D X-ray diffraction, were used for characterisation.3. The humerus had a thinner cortex and cortical bone mineral had higher crystallinity and a greater degree of crystal orientation than the tibiotarsus. The humerus generally lacks medullary bone although, when present, it has a higher mineral content than seen in the tibiotarsus. These differences were attributed to the different forces that stimulate bone formation and remodelling.4. The keel cortical bone had a lower degree of mineralisation than the tibiotarsus or humerus. Its degree of mineralisation decreased from the cranial to the distal end of the bone. This gradient may affect keel mechanical properties, making it more prone to deformation and fractures.5. Data from studying different bones in laying hens can help to understand mineralisation as well as finding solutions to prevent osteoporosis-related fractures.

Dietary phosphorus and calcium in feed affects miRNA profiles and their mRNA targets in jejunum of two strains of laying hens

Phosphorus (P) and calcium (Ca) are critical for egg production in laying hens. Most of P in plant-based poultry diet is bound as phytic acid and needs to be hydrolysed before absorption. To increase P bioavailability, exogenous phytases or bioavailable rock phosphate is added in feed. There is growing evidence of the importance of miRNAs as the epicentre of intestinal homeostasis and functional properties. Therefore, we demonstrated the expression of miRNA profiles and the corresponding target genes due to the different levels of P (recommended vs. 20% reduction) and/or Ca (recommended vs. 15% reduction) in feed. Jejunal miRNA profiles of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) laying hens strains were used (n = 80). A total of 34 and 76 miRNAs were differentially expressed (DE) in the different diet groups within LSL and LB strains respectively. In LSL, the DE miRNAs and their targets were involved in calcium signaling pathway, inositol phosphate metabolism, and mitochondrial dysfunction. Similarly, in LB miRNAs targets were enriched in metabolic pathways such as glutathione metabolism, phosphonate metabolism and vitamin B6 metabolism. Our results suggest that both strains employ different intrinsic strategies to cope with modulated P and Ca supply and maintain mineral homeostasis.

Keratan sulfate as a marker for medullary bone in fossil vertebrates

The ability to determine the sex of extinct dinosaurs by examining the bones they leave behind would revolutionize our understanding of their paleobiology; however, to date, definitive sex-specific skeletal traits remain elusive or controversial. Although living dinosaurs (i.e., extant birds) exhibit a sex-specific tissue called medullary bone that is unique to females, the confident identification of this tissue in non-avian archosaurs has proven a challenge. Tracing the evolution of medullary bone is complicated by existing variation of medullary bone tissues in living species; hypotheses that medullary bone structure or chemistry varied during its evolution; and a lack of studies aimed at distinguishing medullary bone from other types of endosteal tissues with which it shares microstructural and developmental characteristics, such as pathological tissues. A recent study attempted to capitalize on the molecular signature of medullary bone, which, in living birds, contains specific markers such as the sulfated glycosaminoglycan keratan sulfate, to support the proposed identification of medullary bone of a non-avian dinosaur specimen (Tyrannosaurus rex MOR 1125). Purported medullary bone samples of MOR 1125 reacted positively to histochemical analyses and the single pathological control tested (avian osteopetrosis) did not, suggesting the presence of keratan sulfate might serve to definitively discriminate these tissues for future studies. To further test these results, we sampled 20 avian bone pathologies of various etiologies (18 species), and several MB samples. Our new data universally support keratan sulfate as a reliable marker of medullary bone in birds. However, we also find that reactivity varies among pathological bone tissues, with reactivity in some pathologies indistinguishable from MB. In the current sample, some pathologies comprised of chondroid bone (often a major constituent of skeletal pathologies and developing fracture calluses in vertebrates) contain keratan sulfate. We note that beyond chemistry, chondroid bone shares many characteristics with medullary bone (fibrous matrix, numerous and large cell lacunae, potential endosteal origin, trabecular architecture) and medullary bone has even been considered by some to be a type of chondroid bone. Our results suggest that the presence of keratan sulfate is not exclusive evidence for MB, but rather must be used as one in a suite of criteria available for identifying medullary bone (and thus gravid females) in non-avian dinosaur specimens. Future studies should investigate whether there are definite chemical or microstructural differences between medullary bone and reactive chondroid bone that can discriminate these tissues.

Influence of Age and Phylogenetic Background on Blood Parameters Associated With Bone Metabolism in Laying Hens

The high laying performance of today’s laying hens places enormous demands on their mineral metabolism. While up-to-date data are rare, the present study aimed to describe blood parameters associated with egg laying and bone metabolism during the pre-laying period, in the course of the laying period and the daily egg laying cycle. Ten to 15 laying hens of two high-performing, phylogenetically divergent lines (BLA: brown-egg layer; WLA: white-egg layer), kept in single cages were blood sampled at 17, 25, 29, 49, and 69 weeks of age. Sampling was made at 6 a.m., 10 a.m., 2 p.m. and, with the exception of week 17, 6 p.m. Blood samples were analyzed for concentrations of total and ionized calcium, inorganic phosphate (PO4), markers of bone formation (osteocalcin) and resorption [carboxyterminal crosslinked telopeptide of type I collagen (CTX-I)], 25-hydroxycholecalciferol (25(OH)D₃) and estradiol-17β. In the pre-laying period (17 week), the estradiol-17β level calculated for WLA was more than twice as high as the level calculated for BLA, while no significant difference could be observed in the laying period (25 to 69 weeks). BLA hens had significantly higher total calcium concentrations at 49 weeks of age as well as up to twice as high levels of osteocalcin and 25(OH)D₃ than WLA at any time of the day from 25 to 69 weeks of age. While osteocalcin, CTX-I and 25(OH)D₃ concentrations were significantly higher before the onset of lay, total calcium and estradiol-17β levels significantly increased from 17 to 69 weeks of age. In contrast, PO4 values varied only slightly during the experimental period and ionized calcium was highest at 17 and 49 weeks of age and lowest around peak production (29 week). In the course of the daily egg laying cycle blood concentrations clearly reflected the stage of egg formation. Our results provide up-to-date data of bone- and egg laying-associated blood parameters of two contemporary purebred layer lines over the course of the pre- and egg-laying period and the daily egg laying cycle. Differences between brown- and white-egg layers raise questions, whether phylogenetic background determines their efficiency to cope with high calcium demands relating to egg production.

Genetic background and production periods shape the microRNA profiles of the gut in laying hens

There is growing evidence of the importance of miRNAs for intestinal functional properties and nutritional uptake. Comparative miRNAs profiles of the jejunal mucosa were established against two genetic backgrounds (Lohmann Brown-Classic (LB) and Lohmann LSL-Classic (LSL), which are similar in egg production but differ in physiological traits including mineral utilization, along the production periods of laying hens. The target genes of miRNAs higher expressed in LB vs. LSL (miR-126-3p, miR-214, miR-24-3p, miR-726-5p, miR-29b-3p) were enriched for energy pathways at all stages. The target genes of the miRNAs higher in LSL (miR-1788-5p, miR-103-3p, miR-22-5p, miR-221-3p, miR-375) were more enriched for immune and the bone signalling pathways. The most prominent expression differences were between 16 and 24 weeks of age before and after onset of laying. Our results evidence central roles of intestinal miRNAs as regulators of gene expression, influencing intestinal homeostasis and adaptation to environment in different strains and production phases.

Dietary betaine reduces plasma homocysteine concentrations and improves bone strength in laying hens

1. This study tested the hypothesis that the methyl-donor properties of betaine could reduce homocysteine concentrations, which has been recognised in a previous genetics study to be linked to bone quality. This was combined with phytase treatment, as phosphorus is critical for bone mineralisation.2. Using a 2 × 2 factorial arrangement, a total of 1920 Lohmann LSL-lite chickens housed as 24 replicates of 20 chickens were fed one of four diets containing dietary betaine (0 or 1000 mg/kg) and phytase (300 or 1000 FTU/kg) from one day old until end-of-lay. Blood and bone samples were collected at 45 and 70 weeks of age.3. Hens fed betaine had lower plasma homocysteine level (P < 0.05), higher tibia breaking strength (P < 0.05) and higher tibia bone density (P < 0.05).4. Egg production and quality was excellent throughout the study and were not affected by the dietary treatments.5. The addition of dietary betaine was successful at reducing plasma homocysteine concentrations and improving bone strength in laying hens, which could be used as an intervention to alleviate welfare concerns.

Effect of Age on Bone Structure Parameters in Laying Hens

Changes in medullary and cortical bone structure with age remain unclear. Twenty Hy-Line W36 hens, 25 or 52 weeks of age, were euthanized, and both tibiae were collected when an egg was present in the magnum. Serial cross sections of the tibiae were stained with Alcian blue. The bones were scanned using micro-computed tomography. Trabecular width (Tb.Wi) was significantly higher (p < 0.05) in 25-week-old hens, whereas medullary bone tissue volume (TV) was significantly higher (p < 0.01) in 52-week-old hens. 25-week-old hens had significantly higher (p < 0.01) bone volume fraction (BVF = calcified tissue / TV). Moreover, the cortical bone parameters were significantly higher (TV and bone mineral content (BMC) at p < 0.05, and bone volume (BV) and BVF at p < 0.01) in younger hens. Open porosity and total porosity, which indicate less density, were significantly higher (p < 0.01) in older hens. Older hens showed significantly higher (p < 0.01) tibial diaphysis TV than younger hens. Younger hens had significantly higher (p < 0.01) BV, BVF and bone mineral density (BMD) of the tibial diaphysis. These findings reveal that reductions in medullary bone quality might be associated with age-related low estrogen levels and stimulation of osteoclastic bone resorption by parathyroid hormone. Cortical bone quality decreased with enlargement of the Haversian canals and loss of volume, with a longer egg-laying period leading to osteoporosis.

Skeletal health of layers across all housing systems and future research directions for Australia

Modern laying hens have been selected for an astounding rate of egg production, but the physiological calcium demand takes a significant toll on their skeletal health. Bones can be assessed both in vivo and ex vivo, using a combination of different structural and mechanical analysis methods. Typically, the properties of leg, wing and keel bones are measured. Conventional caged layers are restricted in movement, which imbalances structural bone resorption and new bone formation, resulting in osteoporosis. Hens within alternative housing systems have opportunities to exercise for strengthening bones, but they can also suffer from higher rates of keel fractures and/or deviations that are likely to have resulted from collisions or pressure force. Limited research has been conducted within Australian commercial housing systems to assess hen skeletal health, including prevalence of keel damage across different system types. Research conducted on both brown and white hen strains approximately within the past decade internationally (2009 onward) has shown that skeletal health is impaired across all housing systems. Keel-bone damage is of specific concern as it occurs at high rates, particularly in multi-tiered systems, is painful, can alter hen behaviour, and reduce both production and egg quality. Management strategies such as the provision of ramps to access perches and tiers can reduce the incidence of keel-bone damage to a degree. Bone strength can be improved through exercise opportunities, particularly when available during pullet rearing. Genetic selection for high bone strength may be necessary for hens to adequately adapt to loose-housed systems, but the best strategy for improving skeletal health is likely to be multifactorial.

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 application of micro-CT in egg-laying hen bone analysis: introducing an automated bone separation algorithm

The application of micro-CT in small animal research, especially on bone health, has risen exponentially in recent years. However, its application in egg-laying hen bone analysis was still limited. This review introduces the technical aspects of micro-CT in egg-laying hen bone analysis, especially with the medullary bones presented in the cavity. In order to acquate application of micro-CT for laying hen bone research, image acquisition, reconstruction, and analysis settings need to be adjusted properly. The key difference regarding the application of micro-CT in laying hen bone compared to other small animals such as mice and rats was the larger bone size and more complex structures of medullary and trabecular bones. In order to analyze the details of laying hen bone structures, the volume of interest for laying hen should be selected at a region where all 3 bones are present (critical, trabecular, and medullary bone). Owing to the complexity of bone structures, the conventional techniques are not useful to distinguish the trabecular bone and medullary bone in laying hens accurately. In the current review, an automated segmentation algorithm is described to allow researchers to segment bone compartments without human bias. The algorithm is designed according to the morphology difference of medullary bones compared to trabecular and cortical bones. In this procedure, the loosely woven bones were separated by applying dual thresholds. The medullary calcium chunks were separated by opening or closing procedures, where we defined the diameter of medullary chunks being higher than the trabecular bone thickness as a separation trait. The application of micro-CT in laying hen bone health assessment will significantly expand our understanding of chicken bone physiology and osteoporosis, contributing to improve welfare in laying hens.

Role of long-term supplementation of 25-hydroxyvitamin D3 on laying hen bone 3-dimensional structural development

Egg-laying hens have a unique bone development pattern due to the medullary bone formation and high bone turnover rate. The role of long-term supplementation of an intermediate form of vitamin D₃, 25-hydroxyvitamin D₃ (25OHD), on skeletal development of pullets and laying hens is not well established. Exploring its effects on layer bone development will help develop a strategy for preventing laying hen osteoporosis. The purpose of this study was to investigate the role of long-term supplementation of 25OHD in layer diets on bone 3-dimensional structural development. A total of 390 1-day-old Hy-Line W36 pullets were randomly allocated to 3 treatments with 10 replicate cages and 13 birds/cage. Dietary treatments were 1) vitamin D₃ at 2,760 IU/kg, 2) vitamin D₃ at 5,520 IU/kg, and 3) vitamin D₃ at 2,760 IU/kg plus 25OHD at 2,760 IU (69 μg)/kg. The level of 25OHD in the serum was tested throughout the whole experimental period (0–95 wk). Bone growth rate (BGR) was measured at 10 wk using a calcein injection technique. Femurs were scanned using Micro-CT for 3D structural analysis, and the whole-body composition analysis was performed using a dual-energy x-ray absorptiometry method at 17, 60, and 95 wk. Dietary supplementation of 25OHD significantly increased 25OHD level in the serum from 0 to 95 wk. During the rearing period (0–17 wk), 25OHD increased BGR, cortical tissue volume, and bone marrow area at 17 wk, simultaneously. 25OHD created more pores in cortical bone, which resulted in a lower cortical bone mineral density (BMD) but without alerting bone mineral content (BMC). This effect allowed more space for mineral deposition in bones during the later egg-laying period. At 60 wk, the 25OHD group had significantly greater BMD, which led to the highest total BMC, cortical volume, and trabecular bone connectivity. At 95 wk, the birds fed 25OHD had significantly higher cortical bone volume and lower porosity. The 25OHD group also had higher total BMD and medullary bone volume but a lower BMC and volume of trabecular bone than vitamin D₃ or double dosage vitamin D₃ treatment. This indicated that the bone resorption rate was lower in cortical bone than that in trabecular bone in the late laying period. In conclusion, supplementation with dietary 25OHD could stimulate bone growth and increase bone volume in pullets to provide more space for mineral deposition during the laying period with positive effects on laying hen bone quality.

Lead isotopic signatures in blood from incubating common eiders (Somateria mollissima) in the central Baltic Sea

The Christiansø colony of common eiders (Somateria mollissima) in the central Baltic Sea were exposed to high levels of Pb during the 2018 breeding season that were not present in 2017. Due to these high Pb blood levels, the present study investigated possible Pb sources and Pb dynamics within this vulnerable colony. We analyzed body mass and lead isotopic ratios (Pb-IRs) in blood taken from the same incubating eiders at the early (day 4) and late (day 24) stages of incubation during the 2018 breeding season (n = 23). Pb-IRs 208/207, 208/206, 206/207, and 207/206 were analyzed using high resolution inductively coupled mass spectrometry. We found largely similar Pb-IRs from the different stages of incubation indicating a predominantly constant endogenous source of Pb exposure. We suggest the increasing Pb levels come from pre-nesting and nesting foraging and from medullary bone release. The similar Pb-IRs also indicate continued metabolization of the medullary bone to meet the nutritional and energy demands of incubation. Comparisons to Pb-IR reports from the Baltic Sea showed multiple sources of pollution distinguished by a difference between Pb-IRs in individuals with Pb blood concentrations >500 μg/kg ww and <500 μg/kg ww. The most highly contaminated individuals in the present study had Pb-IRs similar to those of Pb ammunition indicating shot pellet uptake. This study further emphasizes the need for continued biomonitoring of the Christiansø colony, including fecal sampling and environmental field sampling to identify the origin and extent of dietary Pb exposure on Christiansø. As a representative unit of the Baltic Flyway population; the Christiansø colony provides an important opportunity for continued investigation into Pb contamination, population dynamics, and declines.

Effects of dietary calcium and available phosphorus levels and phytase supplementation on performance, bone mineral density, and serum biochemical bone markers in aged white egg-laying hens

Exogenous phytase supplementation increases P and Ca availability to allow for the dietary reductions without negative consequences on productivity or skeletal health. Effects of a Buttiauxella sp. phytase (BSP) supplemented in available P (avP)-reduced and Ca-reduced diets on performance, BW, eggshell quality, serum biochemical bone markers, and bone densitometry were evaluated in egg-laying hens from 68 to 78 wk of age. One hundred hens were fed 1 of 5 diets (n = 20/treatment), including a positive control (PC) with 0.35% avP and 3.5% Ca, and the PC moderately reduced in avP and Ca levels by 0.187 and 0.159% of the diet (by 53 and 4.5%), respectively, (NC1) or severely reduced by 0.231 and 0.275% of the diet (by 66 and 7.9%), respectively, (NC2). Other diets were the NC1 or NC2 supplemented with BSP at 600 FTU/kg (NC1 + BSP or NC2 + BSP, respectively). Egg production and feed conversion ratio were maintained by NC1 but were 11.9% lower and 12.3% higher, respectively, with the NC2 than the PC, which was alleviated by supplemental BSP. Diet effects on FI and eggshell quality followed a similar pattern. Body weight was 2.9% lower for NC1, and 6.1% for NC2 than the PC; BSP alleviated the decreased BW. Serum pyridinoline (bone resorption marker) was 20 to 27% higher in NC2 hens than in the other groups, with no effects on other bone markers. Total and trabecular space bone mineral density in the proximal metaphysis were 8.4 and 15.2% lower for NC1, respectively, and 12.1 and 26.7% lower for NC2, respectively, than PC. Supplemental BSP completely alleviated the decreased bone densitometry measures in NC1, but only partially in NC2. The NC1 hens maintained performance but had decreased BW and bone quality; phytase supplementation restored productivity, BW, and bone quality. The Ca and avP deficiencies in the NC2 hens relative to other groups were partially alleviated by the 600 FTU/kg BSP.

Supplemental Nicotinamide Dose-Dependently Regulates Body Phosphorus Excretion via Altering Type II Sodium-Phosphate Co-Transporter Expressions in Laying Hens

BACKGROUND

Dietary supplemental nicotinamide is used to treat hyperphosphatemia in humans. However, the mechanisms of its impact on body phosphorus homeostasis remain unclear.

OBJECTIVE

This study was to determine effects and molecular mechanisms of 3 dietary nicotinamide concentrations on body phosphorus homeostasis in laying hens.

METHODS

Hy-Line Brown layers (total = 21; 40 wk old; body weight: 1,876 ± 24 g) were individually housed (n = 7) and fed a corn-soybean meal-based diet supplemented with nicotinamide at 20 (N20), 140 (N140), and 1000 (N1000) mg/kg for 21 d. Serum phosphorus and fibroblast growth factor 23 (FGF23) concentrations, phosphorus and calcium excretion, and mRNA and/or protein of type II sodium-phosphate co-transporters (NPt2a, NPt2ab) and FGF23 and FGF23 receptors were measured in the intestines, calvaria, kidney, and liver.

RESULTS

Hens in the N1000 group had a 16% lower serum phosphorus concentration and 22% greater phosphorus excretion than those in the N20 or N140 group (P ≤ 0.05). Compared with hens in the N20 group, hens in the N140 and N1000 groups, which did not differ, had 15-21% lower serum FGF23 concentrations, 19-22% greater calcium excretion, 43-56% lower ileum NPT2b protein production, and 1.5- to 1.6-fold greater kidney NPT2a protein production, respectively (all differences at P ≤ 0.05).

CONCLUSIONS

Supplementing high concentrations of nicotinamide in diets for laying hens led to accelerated phosphorus and calcium excretions and decreased serum phosphorus and FGF23 concentrations, which were associated with downregulated intestinal NPt2b protein production. Our findings exclude kidney NPt2a protein production as a primary mechanism for the nicotinamide-induced body phosphorus loss.

Possible roles of parathyroid hormone, 1.25(OH)2D3, and fibroblast growth factor 23 on genes controlling calcium metabolism across different tissues of the laying hen

This study provides an integrative description of candidate gene expression across tissues involved in calcium (Ca) metabolism during the egg laying cycle, using the well-defined model of Ca supply as fine or coarse particles of calcium carbonate (CaCO₃). Plasma and tissue samples were collected from hens at the peak of laying at 0 to 1, 9 to 10, and 18 to 19 h postovulation (PO). After mRNA preparation from the parathyroid gland, medullary bone, liver, kidney, duodenum, and jejunum, gene expressions were quantified using RT-qPCR. The highest levels of parathyroid hormone (PTH) mRNA in the parathyroid gland (P < 0.05), and of the active form of vitamin D₃ 1.25(OH)₂D₃ in the plasma (P < 0.01) were observed at 18 to 19 h PO. During this active phase of eggshell formation, bone resorption was attested to high levels of plasma inorganic phosphorus (iP) and the receptor activation of nuclear factor-κB expression in the bone (P < 0.001 and P < 0.05, respectively). At this stage, 5 genes of the transcellular and the paracellular Ca absorption pathways in the intestine (P < 0.05) and the Ca channel transient receptor potential cation channel subfamily V member 5 (P < 0.05), involved in its reabsorption in the kidney, were overexpressed. At 0 to 1 h PO during the subsequent daylight period, 2 candidates of the transcellular and the paracellular Ca pathways (P < 0.05) remained at high levels in the intestine, while calbindin D 28K expression was the highest in the kidney (P < 0.05). As PTH mRNA and 1.25(OH)₂D₃ were low, bone accretion was likely active at this stage. The phosphaturic hormone fibroblast growth factor 23 (FGF23) was overexpressed at 18 to 19 h PO (P < 0.05) in the bone when plasma iP was high, which suggested a role in the subsequent reduction of P reabsorption in the kidney, as attested to the decreased expression of P cotransporters, leading to iP clearance from the plasma at 0 to 1 h PO (P < 0.05). The low levels of 1.25(OH)₂D₃ at this stage coincided with increased expression of the 24-hydroxylase gene in the kidney (P < 0.05). In hens fed fine particles of CaCO₃, higher plasma levels of 1,25(OH)₂D₃ and higher expression of several genes involved in bone turnover reflected a stronger challenge to Ca homeostasis. Altogether, these data support the hypothesis that FGF23 could drive vitamin D metabolism in the laying hen, as previously documented in other species and explain the tight link between P and Ca metabolisms.

Various bone parameters are positively correlated with hen body weight while range access has no beneficial effect on tibia health of free-range layers

The aim of this study was to determine if body weight or range use has a significant impact on bone health in commercial free-range laying hens, and to correlate tibia bone quality parameters with individual range usage and body weight. A total of 30 Lohmann Brown hens at 74 wk of age were selected from a commercial free-range farm and were either classified as heavy (mean ± SEM body weight 2.11 ± 0.034 kg, n = 14) or light (1.68 ± 0.022 kg, n = 16) body weight, and also classified as rangers (accessed the range for 86.7% of available days, n = 16) or stayers (accessed the range for 5.00% of available days, n = 14). The left tibiae of all individuals were analyzed for morphological parameters using computed tomography, evaluated for bone breaking strength, and ashed to determine mineral composition. Keel bone scoring was performed based on observation. Data were analyzed using a 2 × 2 factorial ANOVA, and regression analysis was performed. There was no measurable effect of range usage on any of the tibia parameters investigated. The body weight was significantly correlated with tibia breaking strength (r = 0.59), tibia weight (r = 0.56), tibia length (r = 0.64), diaphyseal diameter (r = 0.61), and total tibia volume (r = 0.67). In conclusion, range access had no beneficial effect on bone health. The impact of internal hen house furnishing and movement on bone health needs further investigation.

Effects of phytase supplementation on eggshell and bone quality, and phosphorus and calcium digestibility in laying hens from 25 to 37 wk of age

Effects of dietary available phosphorus (aP) and Ca levels and an Escherichia coli 6-phytase supplementation were studied in Lohmann LSL-Lite hens from 25 to 37 wk of age. Eighty-four hens were used in a completely randomized design with 7 treatments. The treatments were a positive control (PC) diet with 0.45% aP, 3.70% Ca, and 0.16% Na from 25 to 28 wk and 0.38% aP, 3.73% Ca, and 0.15% Na from 29 to 37 wk; a negative control (NC) diet, similar to the PC diet, with 0.22% aP, 3.00% Ca, and 0.13% Na from 25 to 28 wk and 0.19% aP, 3.02% Ca, and 0.13% Na from 29 to 37 wk; the NC diets supplemented with phytase at 150 (NC + 150), 300 (NC + 300), 600 (NC + 600), or 1,200 (NC + 1,200) phytase unit (FTU)/kg; and the PC diet supplemented with phytase at 1,200 (PC + 1,200) FTU/kg. Hen performance, eggshell, and bone quality were measured on a 4-wk basis. Bone breaking strength and ash and apparent ileal digestibility (AID) of P and Ca were determined at 37 wk. One- and 2-way ANOVA were conducted, and Tukey's range test was used to compare multiple means where P ≤ 0.05. No differences in hen performance, eggshell quality, bone breaking strength, bone ash, and P digestibility were observed between the PC and the NC treatments. The NC hens had lower cortical (P < 0.001) and trabecular + medullary bone mineral density (P = 0.004) and total bone mineral content (P < 0.001) than the PC hens. The PC + 1,200 increased cortical bone mineral density (P < 0.001). The reductions of aP and Ca in the NC diet were not deficient for performance but had a minor impact on bone mineralization. The NC + 600 and NC + 1,200 increased AID of P (P = 0.024), and all phytase treatments except the NC + 150 increased AID of Ca (P = 0.010) compared with the NC diet.

Identifying medullary bone in extinct avemetatarsalians: challenges, implications and perspectives

Medullary bone (MB) is a sex-specific tissue produced by female birds during the laying cycle, and it is hypothesized to have arisen within Avemetatarsalia, possibly outside Avialae. Over the years, researchers have attempted to define a set of criteria from which to evaluate the nature of purported MB-like tissues recovered from fossil specimens. However, we argue that the prevalence, microstructural and chemical variability of MB in Neornithes is, as of yet, incompletely known and thus current diagnoses of MB do not capture the extent of variability that exists in modern birds. Based on recently published data and our own observations of MB distribution and structure using computed tomography and histochemistry, we attempt to advance the discourse on identifying MB in fossil specimens. We propose: (i) new insights into the phylogenetic breadth and structural diversity of MB within extant birds; (ii) a reevaluation and refinement of the most recently published list of criteria suggested for confidently identifying MB in the fossil record; (iii) reconsideration of some prior identifications of MB-like tissues in fossil specimens by taking into account the newly acquired data; and (iv) discussions on the challenges of characterizing MB in Neornithes with the goal of improving its diagnosis in extinct avemetatarsalians. This article is part of the theme issue 'Vertebrate palaeophysiology'.

Candidate genes of the transcellular and paracellular calcium absorption pathways in the small intestine of laying hens

To meet the high calcium (Ca) demand during eggshell biomineralization (2 g of Ca per egg), laying hens develop specific metabolic regulations to maintain Ca homeostasis. The intake of Ca, its solubilization, and absorption capacity are enhanced at sexual maturity (SM). A better knowledge of the intestinal Ca transporters involved in their variations at this stage could indicate new nutritional strategies to enhance Ca digestive utilization. Transcellular Ca absorption pathway and its major player calbindin-D 28 K (CALB1) mediate a saturable transport, which has been extensively described in this model. Conversely, a contribution by the paracellular pathway involving non-saturable Ca transport through intercellular tight junction has also been suggested. The aim of the present study was to identify candidate genes of these two pathways and their patterns of expression, in immature pullets (12, 15, and 17 wk old) and mature laying hens (23 wk old) in the duodenum, jejunum, and ileum. Using RT-qPCR, this study identifies 3 new candidate genes for transcellular, and 9 for paracellular Ca transport. A total of 5 candidates of the transcellular pathway, transient receptor potential cation channels subfamily C member 1 (TRPC1) and M member 7 (TRPM7); CALB1 and ATPase plasma membrane Ca²⁺ transporting 1 (ATP2B1) and ATPase plasma membrane Ca²⁺ transporting 2 (ATP2B2) were enhanced with age or after SM in the duodenum, the jejunum or all 3 segments. A total of 4 candidates of the paracellular pathway Claudin 2 (CLDN2) and tight junction proteins 1, 2, and 3 (TJP1, TJP2 and TJP3) increased in the small intestine after SM. Additionally, CALB1, ATP2B2, and CLDN2 were overexpressed in the duodenum or the jejunum or both segments after SM. The enhanced expression of candidate genes of the paracellular Ca pathway after SM, supports that the non-saturable transport could be a mechanism of great importance when high concentrations of soluble Ca are observed in the intestinal content during eggshell formation. Both pathways may work cooperatively in the duodenum and jejunum, the main sites of Ca absorption in laying hens.

Dietary supplementation with protected calcium effects production and egg quality of Hy-line brown laying hens

Context Currently, the commonly used dietary calcium sources are not sufficiently bioavailable to be used for eggshell formation or bone health in laying hens. Protected calcium, a blend of calcium and medium-chain fatty acids with matrix coating, may exert an effective absorption and metabolism ability for calcium consumption in the laying hen. Aims The present study was conducted to evaluate the effects of protected-calcium supplementation on egg production, egg quality, and serum calcium and phosphorus concentrations in laying hens. Methods In total, 144 Hy-line brown laying hens (25 weeks old) were randomly allotted to three treatments (8 replicates with 6 hens, 1 hen per cage) in a 10-week trial. Treatments consisted of corn–wheat–soybean meal-based basal diet with limestone (coarse limestone:fine limestone = 50:50) as a calcium source (CON) or basal diet supplemented with 0.5% (P1) or 1% (P2) protected calcium in substitution for an equal quantity of coarse limestone. Data were statistically analysed using linear and quadratic contrast with the GLM procedure of SAS. Probability values of &lt;0.05 indicate significance. Key results At Weeks 31–33 and 35, the cracked-egg rates were lower in the P1 and P2 groups than in the CON group (P &lt; 0.05; linear, P &lt; 0.05) and, at Weeks 29 and 34, the cracked-egg rates in the P2 group were also significantly (P &lt; 0.05) decreased. At Weeks 26, 30 and 32, the Haugh units in the P2 group were significantly (P &lt; 0.05) higher than those in the CON group. In addition, eggshell strength was increased significantly (P &lt; 0.05) in the P2 group at Weeks 26, 27 and 31–35. The serum calcium concentration of the P2 group was significantly (P &lt; 0.05) greater than that of the CON group in the morning. Conclusions In conclusion, a replacement of limestone with 1% protected calcium can increase eggshell quality. Implications Protected-calcium supplementation can be used in practice for decreasing the breakage of eggs.

High-resolution large-area imaging of nanoscale structure and mineralization of a sclerosing osteosarcoma in human bone

Osteosarcoma is the most common primary bone cancer type in humans. It is predominantly found in young individuals, with a second peak later in life. The tumour is formed by malignant osteoblasts and consists of collagenous, sometimes also mineralized, bone matrix. While the morphology of osteosarcoma has been well studied, there is virtually no information about the nanostructure of the tumour and changes in mineralization on the nanoscale level. In the present paper, human bone tissue inside, next to and remote from a sclerosing osteosarcoma was studied with small angle x-ray scattering, x-ray diffraction and electron microscopy. Quantitative evaluation of nanostructure parameters was combined with high resolution, large area mapping to obtain microscopic images with nanostructure parameter contrast. It was found that the tumour regions were characterized by a notable reduction in mineral particle size, while the mineral content was even higher than that in normal bone. Furthermore, the normal preferential orientation of mineral particles along the longitudinal direction of corticalis or trabeculae was largely suppressed. Also the bone mineral crystal structure was affected: severe crystal lattice distortions were detected in mineralized tumour tissue pointing to a different ion substitution of hydroxyl apatite in tumorous tissue than in healthy tissue.

Evaluation of a new generation phytase on phytate phosphorus release for egg production and tibia strength in hens fed a corn-soybean meal diet

To test the effect of several inclusion levels of Citrobacter braakii phytase (CBP), on phytate P release, 420 50-wk-old-Bovans White hens were randomly allocated to 7 treatments with 5 replicates of 12 hens each. The experimental period lasted 12 weeks, first 8 for adaptation and last 4 for data collection. Feed and water were provided ad libitum. Treatments were: (1) a 0.12% basal corn-soybean meal diet deficient only in non-phytate P. Treatments 2 and 3 were added with constant increases of 0.11% inorganic P, to get a linear hen response to P addition. Treatments 4 to 7 were the addition of 300; 600; 1,200; and 1,800 phytase units (FYT)/kg to the basal diet. Variables analyzed were hen productive performance (HPP) and tibia resistance to fracture (TRF), and mineral content. Data were analyzed as a Complete Randomized Design (CRD). The results from treatments 1 to 3 were analyzed by a regression model to test for a significant linear response (P < 0.05). Then for every level of CBP added (treatments 4 to 7), the linear regression equation was solved to find out the equivalent value of released P. Based on hen health and welfare, the response variables that yielded realistic P equivalence values for the CBP levels used in the present trial were the tibia data. Following the significant (P < 0.001) linear response, the equations; TRF, kg (Y = 28.16X + 17.42 R² = 0.84); Tibia Ca, % (Y = 11.6X + 14.2 R² = 0.80); Tibia P, % (Y = 11.6X + 6.1 R² = 0.81); and T ash, % (Y = 33.3X + 38.1 R² = 0.80). Under the experimental conditions of this trial, the HPP variables were not a sensitive parameter to measure P release; whereas, tibia parameters showed the following average P release values per level of CBP inclusion in the corn- soybean meal diet; 300 FYT/kg = 0.099%, 600 FYT/kg = 0.141%, 1,200 FYT/kg = 0.182%, and 1,800 FYT/kg = 0.198%.