Effects of age and dietary soybean oil level on eggshell quality, bone strength and blood biochemistry in laying hens

Quantitative lipidomics reveals the changes of lipids and antioxidant capacity in egg yolk from laying hens with fatty liver hemorrhagic syndrome

In laying hens, fatty liver hemorrhagic syndrome (FLHS) is a common metabolic disorder, which can affect egg production and nutritional value. However, the impact of FLHS on the lipid content in egg yolks was not clear. In this study, FLHS model was induced by using high-energy low-protein diet, and the egg quality was evaluated. Egg yolk lipids were quantitatively analyzed by using ultra-performance liquid chromatography-mass spectrometry combined with multivariate statistical analysis. Gene expressions of the lipoprotein were determined by qRT-PCR and antioxidant capacity of the egg yolk were determined by kits. The elevated blood lipids and extensive lipid droplets observed indicated successful establishment of the FLHS model in laying hens. Measurements of egg quality showed that egg yolk weight was increased in the FLHS group. Lipidomics revealed that 1,401 lipids, comprising 27 lipid subclasses in the egg yolk. According to score plots of principal component analysis and orthogonal partial least squares discriminant analysis, different lipid profile was observed between the control and FLHS groups. A total of 97 different lipid species were screen out. Sphingolipid and glycerophospholipid metabolism were identified as key pathways. Free polyunsaturated fatty acids (PUFA) exhibited an increase in the FLHS group (P < 0.05). Notably, the form of PUFAs was changed that the FLHS group showed an increase in triacylglycerol-docosahexenoic acid and triacylglycerol-arachidonic acid in the egg yolk, while triacylglycerol-α-linolenic acid was decreased (P < 0.05). Total superoxide dismutase was decreased in the egg yolks affected by FLHS. Gene expressions of vitellogenin 2 (VTG2), VTG3, very low-density apolipoprotein II and apolipoprotein B were increased in the liver of laying hens with FLHS (P < 0.05). In conclusion, FLHS promoted the lipid transport from the liver to the yolk by upregulating lipoprotein expression, which altered lipid profile, and reduced antioxidant capacity in the yolk. This study provided a foundation for understanding the changes in lipids, lipid transport and lipid antioxidation capacity in egg yolk from laying hens with FLHS.

Decreased eggshell strength caused by impairment of uterine calcium transport coincide with higher bone minerals and quality in aged laying hens

BACKGROUND

Deteriorations in eggshell and bone quality are major challenges in aged laying hens. This study compared the differences of eggshell quality, bone parameters and their correlations as well as uterine physiological characteristics and the bone remodeling processes of hens laying eggs of different eggshell breaking strength to explore the mechanism of eggshell and bone quality reduction and their interaction. A total of 240 74-week-old Hy-line Brown laying hens were selected and allocated to a high (HBS, 44.83 ± 1.31 N) or low (LBS, 24.43 ± 0.57 N) eggshell breaking strength group.

RESULTS

A decreased thickness, weight and weight ratio of eggshells were observed in the LBS, accompanied with ultrastructural deterioration and total Ca reduction. Bone quality was negatively correlated with eggshell quality, marked with enhanced structures and increased components in the LBS. In the LBS, the mammillary knobs and effective layer grew slowly. At the initiation stage of eggshell calcification, a total of 130 differentially expressed genes (DEGs, 122 upregulated and 8 downregulated) were identified in the uterus of hens in the LBS relative to those in the HBS. These DEGs were relevant to apoptosis due to the cellular Ca overload. Higher values of p62 protein level, caspase-8 activity, Bax protein expression and lower values of Bcl protein expression and Bcl/Bax ratio were seen in the LBS. TUNEL assay and hematoxylin-eosin staining showed a significant increase in TUNEL-positive cells and tissue damages in the uterus of the LBS. Although few DEGs were identified at the growth stage, similar uterine tissue damages were also observed in the LBS. The expressions of runt-related transcription factor 2 and osteocalcin were upregulated in humeri of the LBS. Enlarged diameter and more structural damages of endocortical bones and decreased ash were observed in femurs of the HBS.

CONCLUSION

The lower eggshell breaking strength may be attributed to a declined Ca transport due to uterine tissue damages, which could affect eggshell calcification and lead to a weak ultrastructure. Impaired uterine Ca transport may result in reduced femoral bone resorption and increased humeral bone formation to maintain a higher mineral and bone quality in the LBS.

Fermented calcium butyrate supplementation in post-peak laying hens improved ovarian function and tibia quality through the "gut-bone" axis

The compromised egg quality and leg abnormality during the end of the laying cycle (after 40 weeks) have been leading to poor animal welfare and substantial economic losses. Therefore, the effects of fermented calcium (Ca) butyrate, produced by fermentation by Clostridium butyricum, on production, eggshell quality, and tibial property of hens were explored. A total of 192 Hy-line brown laying hens at 50-week-old were assigned to a basal diet or the basal diet with 300 mg/kg of the fermented Ca butyrate from 50 to 58 weeks of age. Each treatment had 6 replicates with 16 hens each. The diet supplemented with 300 mg/kg fermented Ca butyrate notably increased egg weight, ovarian follicle number, and eggshell strength (P = 0.072) as compared to the basal diet, which were associated with cytokine secretion, toll-like receptor signaling pathways, and intestinal immunity based on the RNA-seq data from the granulosa. Dietary Ca butyrate inclusion decreased the expression of ileal tumor necrosis factor-alpha and serum pro-inflammatory cytokine concentration, as well as increased the content of serum immunoglobulin A when compared to the basal diet (both P < 0.05). The birds that received fermented Ca butyrate diets exhibited higher villus height (P < 0.05) and upregulated expression of tight junction proteins, whereas it did not alter the composition of cecal microbiota (P > 0.05). In addition, the diet with fermented Ca butyrate reduced the number of osteoclasts in the proximal tibia and the level of C-terminal cross-linked telopeptide of type I collagen, a bone resorption marker (P < 0.05), whereas it tended to increase the concentration of the procollagen type I N-terminal propeptide that reflects bone formation marker in serum. Moreover, the layers fed fermented Ca butyrate diets possessed higher (P < 0.05) bone area and trabecular number of the proximal tibia, yield load, and ultimate load than those that consumed basal diets. Collectively, dietary fermented Ca butyrate supplementation in post-peak layer diets improved the ovarian function and tibia quality, which might be related to enhancing intestinal integrity and consequently decreasing inflammation mediated bone resorption.

Superiority of coarse eggshell as a calcium source over limestone, cockle shell, oyster shell, and fine eggshell in old laying hens

Chicken eggshell (ES) waste is a rich source of calcium carbonate (CaCO3); however, the potential of ES as dietary calcium (Ca) in old laying hens has not been explored. This study compared the effects of feeding limestone, cockle shell, oyster shell, fine ES, and coarse ES as the sole Ca source on production performance, egg quality, blood biochemical constituents, and tibia characteristics in old laying hens. A total of 450 ISA-Brown laying hens at 73 wk of age with similar egg production rate (EPR) were randomly assigned to 5 treatment groups (90 hens/group, 9 hens/replicate) for 7 wk. Dietary treatment groups comprised a corn-soybean meal based diet containing different Ca sources: (i) limestone (LS; < 2 mm and 2-4 mm mixed in the ratio of 3:7) as control, (ii) cockle shell (CS; 1-4 mm), (iii) oyster shell (OS; 3-16 mm), (iv) ES fine particles (ESF; < 1 mm), and (v) ES coarse particles (ESC; 3-5 mm). Results indicated that dietary inclusion of coarse ES particles significantly increased average egg weight (P < 0.001) and daily egg mass (P < 0.05), and decreased feed conversion ratio (P < 0.001) as compared with the other treatments. However, no significant differences in EPR, feed intake, cracked egg proportion, and mortality were observed among the dietary treatments (P > 0.05). Notably, the use of ESF led to a lower proportion of cracked eggs than ESC (P < 0.05). ESC fed hens produced the heaviest eggs whereas CS fed hens produced the lightest (P < 0.001); the particle size of ES also affected the egg weight (P < 0.05). The eggs from OS and ESC fed hens showed a greater albumen height in comparison to eggs from CS group (P < 0.05); but no significant difference was observed among the LS, OS, ESF, and ESC groups (P > 0.05). The yolk color was darker in the eggs of group ESF as compared with other dietary groups (P < 0.01). However, no significant effects on Haugh units and shell properties were observed among the treatments (P > 0.05). The blood biochemistry results were not affected by the dietary Ca (P > 0.05) except for lower levels of high-density lipoprotein percentage (HDL %) in OS and ESC fed hens (P < 0.05). The tibia characteristics including weight, length, width, and breaking strength did not differ among the dietary groups (P > 0.05). However, the ESC and OS fed hens showed higher tibia bone mineral density (BMD) than the other groups (P < 0.001). In conclusion, coarse ES as a sole Ca source had beneficial effects on the production performance, egg quality, and tibia BMD in old laying hens.

Dietary Soybean Oil Supplementation Affects Keel Bone Characters and Daily Feed Intake but Not Egg Production and Quality in Laying Hens Housed in Furnished Cages

To evaluate dietary soybean oil supplementation on production performance, egg quality, and keel bone health in laying hens. Two hundred and four laying hens at 20 weeks of age (WOA) were distributed into 12 cages containing 17 birds each. Birds were either fed a commercial diet (control group, CON) or a diet supplemented with 3% of soybean oil (SO group). Experiments lasted 17 weeks. Body weight, daily feed intake, production performance and egg quality were measured at 25, 29, 33, and 37 WOA. Birds were subsequently assessed for keel bone status by palpation, and keel was excised to measure bone length, microstructure, bone mineral density (BMD), elements contents, and the expression of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), collagen type II alpha 1 (COL2α1), periostin (POSTN), and sclerostin (SOST). The results showed that dietary SO supplementation did not affect production performance and egg quality (P > 0.05), but improved body weight of hens at 29 and 37 WOA (P < 0.05), and decreased daily feed intake at 33 and 37 WOA (P < 0.05). Incidence of keel bone damage (especially fracture) was higher in hens of SO group. Keel bone length in birds of SO group was significantly decreased compared to CON (P < 0.05). Keel bone of supplemented hens showed increased trabecular separation at 29 WOA and higher levels of V, Mn, Fe, Se, and Ba at 33 WOA (P < 0.05). Moreover, decreased BMD, trabecular number and thickness were observed in keel bone of laying hens receiving supplementation at 29 and 37 WOA (P < 0.05); decreased levels of Li, Ca, Hg, and TI at 33 WOA and trabecular thickness at 37 WOA (P < 0.05) were also identified. mRNA levels of SOST and RANKL and the ratio of RANKL/OPG mRNA levels were increased in birds fed a SO-supplemented diet (P < 0.05); COL2α1, OPG, and POSTN were downregulated at all sampling points (P < 0.05). Taken together, results indicate that feeding laying hens a diet supplemented with soybean oil can decrease daily feed intake and impair keel bone health but not influence production performance and egg quality.

Prolonged scotophase within a 24 hour light regime improves eggshell quality by enhancing calcium deposition in laying hens

Calcium (Ca) and phosphorus (P) transporters are responsible for their absorption and transport in small intestine and kidney, contributing to eggshell formation. The light-dark cycle is a primary cue in the reproduction of laying hen. In this study, we investigated the effect of different light-dark programs on eggshell quality and the expression of genes related to Ca and P transportation in laying hens. Seventy-two 56-week-old laying hens were randomly divided into two groups and reared at 16-h light and 8-h dark (control) or 9-h light and 15-h dark regime (long dark phase, LDP). The expressions of calcium transporter calbindin-D28k (CaBP-D28k), plasma membrane Ca ATPase 1b (PMCA1b), and phosphorus transporter NaPi-IIb (NPt2b) and NaPi-IIa (NPt2a) were measured in the small intestine, kidney, and eggshell gland. The results showed that feed intake (P < 0.001) and egg weight (P = 0.05) were decreased by LDP treatment. Compared with control, the eggshell hardness was increased (P = 0.011) by LDP treatment, but the eggshell thickness and the percentage of eggshell were not changed. The Ca and P contents in eggshell were increased by LDP treatment. During the scotophase, LDP-hens showed higher serum Ca (P = 0.0056) and P levels (P = 0.079) but lower alkaline phosphatase (ALP) activity than that of control hens. In the duodenum, the relative higher expression of CaBP-D28k and PMCA1b in scotophase compared to photophase was masked by LDP treatment. The expression of CaBP-D28k and osteopontin (OPN) in the eggshell gland were increased by LDP treatment, compared to control hens. In the jejunum, the protein expression levels of CaBP-D28k and PMCA1b decreased during photophase in LDP-hens. The result indicates that the increased blood Ca and P concentration during scotophase by LPD treatment is beneficial to the deposition of Ca and P in the eggshell. The result offers an alternative strategy for managing laying hens with poor eggshell quality.

A comparison of intestinal integrity, digestive function, and egg quality in laying hens with different ages

Intestinal integrity, digestive enzyme activity, nutrient utilization, and egg quality of laying hens at different ages were evaluated and compared in this study. A total of 192 Hy-line Brown laying hens at 195-d-old (D195 group), 340-d-old (D340 group), and 525-d-old (D525 group) were allocated into one of 3 groups in accordance with their ages. Each group had 8 replicates of 8 birds each, and all birds were fed a maize-soybean meal basal diet for a 2-wk experiment. Compared with the D195 group, intestinal villus height and ratio of villus height to crypt depth, as well as serum D-lactate content increased in the D525 group (P < 0.05). The sucrase and maltase activities in the jejunal mucosa, amylase activity in the pancreas, and trypsin activity in the jejunal chyme of 525-d-old hens were lower than their 195-d-old counterparts (P < 0.05). In addition, there was a decline of trypsin and lipase activities in the ileal chyme of hens from D525 group in comparison with D195 or D340 group (P < 0.05). Apparent retention of dry matter and crude protein of birds in D340 and D525 group decreased when compared with the D195 group (P < 0.05). Moreover, birds in the D525 group exhibited a lower level of ether extract retention, and higher contents of several excreted amino acids than those in the D195 group (P < 0.05). Compared with the D195 group, eggs harvested from D525 group exhibited lower albumen height, eggshell strength and thickness, and a higher egg weight (P < 0.05). In conclusion, increased intestinal permeability (higher serum D-lactate content), compromised digestive function (lower digestive enzyme activities and apparent nutrient retention, and higher concentrations of excreted amino acids), and poor egg quality (lower albumen height, eggshell strength, and thickness) were observed with increasing age in the laying hens.

Effect of laying hens age and housing system on physicochemical characteristics of eggs

In this study, the objective was to evaluate the effect of the age of Hy-line Brown hens – 44 and 60 weeks of age (26 and 42 weeks of laying) and housing system (enriched cages and litter) on the quality of eggs. According to our results, eggs with a better quality of albumen were obtained from younger hens than from older hens. Moreover, older hens produced eggs with inferior quality related to shell parameters, such as greater elastic deformation, poorer breaking strength, and thinner shells. However, hens kept in a litter housing system laid eggs with superior shell quality characteristics of less flexible and greater breaking strength, even though the thickness, weight, and percentage were similar in both housing systems. In addition, a higher amount and activity of lysozyme were obtained from eggs laid by hens kept in the litter housing system than those obtained from hens kept in cages. The maintenance system and age of birds also had a significant (P≤0.05) effect on the basic chemical composition of eggs, as well as on the proportion of individual elements and fatty acid profile. Taking these results into account, we can conclude that the more valuable characteristics from the morphological and nutritional point of view were observed in eggs obtained from younger Hy-line hens kept in the litter housing system.

Osteocalcin prevents insulin resistance, hepatic inflammation, and activates autophagy associated with high-fat diet-induced fatty liver hemorrhagic syndrome in aged laying hens

The aim of this study was to investigate the effects of osteocalcin (OCN) on fatty liver hemorrhagic syndrome (FLHS) in aged laying hens. Thirty 68-week-old White Plymouth laying hens were randomly assigned into conventional single-bird cages, and the cages were randomly allocated into one of 3 treatments (n = 10): normal diet (ND + vehicle, ND + V), high-fat diet (HFD + vehicle, HFD + V), and HFD + OCN (3 μg/bird, 1 time/2 d, i.m.) for 40 d. At day 30, oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were performed. At the end of experiment, the hens were euthanized followed by blood collection. The plasma aspartate transaminase (AST), alkaline phosphatase (ALP), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were measured using an automatic biochemistry analyzer. Pathological changes in the liver were examined under both light and transmission electron microscopes. The plasma inflammatory factors including interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-α) were analyzed by ELISA, and the gene expressions of these inflammatory factors in the liver were analyzed by real-time PCR. The level of oxidative stress was evaluated using malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) assay kits, respectively. The results showed that HFD + V hens had more severe liver hemorrhage and fibrosis than ND + V hens (P < 0.05). The ultramicrostructural examination showed that hepatocytes of HFD + V hens exhibited necrotic pyknosis showing great intracellular electron, mitochondrial swelling, shrunk nucleus, and absence of autolysosomes. Osteocalcin mitigated HFD + V-induced pathological changes in aged laying hens. High-fat diet + OCN hens had higher insulin sensitivity; lower liver concentrations of MDA (P = 0.12) but higher GSH-Px (P < 0.05); and lower blood TNF-α concentrations (P < 0.05) and mRNA expressions (P < 0.05) than HFD + V hens. These results suggest OCN functions in preventing the FLHS process in old laying hens through inhibiting excessive energy diet-induced metabolic disorder, oxidative stress, and related pathological damage.

Physical and mechanical properties of eggshell as affected by chicken breed and flock age

1. A study was conducted to evaluate the relationship among physical and mechanical properties of the eggshell, as affected by breed and hen's age. 2. Data on eggshell quality (external characteristics and derived measurements) were obtained from 322 laying hens, from three breeds (Fayoumi, Dandarawi and Hy-Line Brown) during the laying cycle, starting from 38 wks of age for four experimental periods (38, 46, 54 and 62 wks). 3. Eggs obtained from the Fayoumi breed exhibited the highest shell thickness and breaking force. There was a linear improvement in eggshell quality attributes associated with hen's age up to 54 wks, thereafter a deterioration was found for all breeds. 4. Generally, eggs laid by native breeds (Fayoumi and Dandarawi) had better mechanical properties compared to those produced by the commercial strain (Hy-Line Brown). In addition, the interaction between breed and hen's age was not significant for any physical property or mechanical attribute. There was a highly significant (P ≤ 0.01) positive correlation between the breaking force and either eggshell toughness or shell thickness, and regression analyses suggested that eggshell toughness was the best predictor for breaking force, followed by shell thickness.

Expression of pro- and anti-inflammatory cytokines and chemokines during the ovulatory cycle and effects of aging on their expression in the uterine mucosa of laying hens

The aim of this study was to examine whether cytokines and chemokines expressed in the uterine mucosa play a role in the process of eggshell formation in the chicken uterus. Changes in the expression levels of pro- and anti-inflammatory cytokines and chemokines in the uterine mucosa during an ovulatory cycle (experiment 1) and effects of aging on their expression (experiment 2) were examined. In experiment 1, the expression of the pro-inflammatory cytokines IL1β, IL6, TNFSF15, and IFNγ, and a chemokine CX3CL1 was found to increase during eggshell biomineralization (16 h following oviposition), while anti-inflammatory TGFβ2 expression was found to increase at 4 h following oviposition. In experiment 2, a higher expression of the anti-inflammatory cytokines TGFβ2 and TGFβ3, and chemokines CXCLi2 and CX3CL1, was observed in aged hens than in young hens. A significantly higher number of macrophages and CD8+ T cells were observed in the uterine tissue of aged hens than in young hens. Furthermore, the expression of adhesion molecules associated with leukocytic infiltration was found to be higher in aged hens than in young hens. We conclude that the eggshell formation process may be affected by the pro- and anti-inflammatory cytokines and chemokines. The balanced expressions of these molecules might be disrupted in aged hens.