Search Results (203)

Background: Reliable and non-invasive methods for assessing welfare in poultry are essential for improving evidence-based welfare monitoring and advancing management practices in commercial production systems. The iris-to-pupil (IP) ratio, previously validated by our group in primates and cattle, reflects autonomic nervous system balance and may serve as a physiological indicator of stress in laying hens. This study evaluated the utility of the IP ratio under field conditions across diverse commercial layer housing systems. Materials and Methods: In total, 296 laying hens (Lohmann Brown, n = 269; White Leghorn, n = 27) were studied across four locations in Canada housed under different systems: Guelph (indoor; pen), Spring Island (outdoor and scratch; organic), Ottawa (outdoor, indoor and scratch; free-range), and Toronto (outdoor and hobby; free-range). High-resolution photographs of the eye were taken under ambient lighting. Light intensity was measured using the light meter app. The IP ratio was calculated using NIH ImageJ software (Version 1.54p). Statistical analysis included one-way ANOVA and linear regression using GraphPad Prism (Version 5). Results: Birds housed outdoors had the highest IP ratios, followed by those in scratch systems, while indoor and pen-housed birds had the lowest IP ratios (p < 0.001). Subgroup analyses of birds in Ottawa and Spring Island farms confirmed significantly higher IP ratios in outdoor environments compared to indoor and scratch systems (p < 0.001). The IP ratio correlated weakly with ambient light intensity (r² = 0.25) and age (r² = 0.05), indicating minimal influence of these variables. Although White Leghorn hens showed lower IP ratios than Lohmann Browns, this difference was confounded by housing type; all White Leghorns were housed in pens. Thus, housing system but not breed was the primary driver of IP variation. Conclusions: The IP ratio is a robust, non-invasive physiological marker of welfare assessment in laying hens, sensitive to housing environment but minimally influenced by light or age. Its potential for integration with digital imaging technologies supports its use in scalable welfare assessment protocols. Full article

Rooster behavior and activity are critical for egg fertility and hatchability in broiler and layer breeder houses. Desirable roosters are expected to have good leg health, reach sexual maturity, be productive, and show less aggression toward females during mating. However, not all roosters are desirable, and low-productive roosters should be removed and replaced. The objectives of this study were to apply an object detection model based on deep learning to identify hens and roosters based on phenotypic characteristics, such as comb size and body size, in a cage-free (CF) environment, and to compare the performance metrics among the applied models. Six roosters were mixed with 200 Lohmann LSL Lite hens during the pre-peak phase in a CF research facility and were marked with different identifications. Deep learning methods, such as You Only Look Once (YOLO) models, were innovated and trained (based on a comb size of up to 2500 images) for the identification of male and female chickens based on comb size and body features. The performance matrices of the YOLOv5u and YOLOv11 models, including precision, recall, mean average precision (mAP), and F1 score, were statistically compared for hen and rooster detection using a one-way ANOVA test at a significance level of p < 0.05. For rooster detection based on comb size, YOLOv5lu, and YOLOv11x variants performed the best among the five variants of each model, with YOLOv5lu achieving a precision of 87.7%, recall of 56.3%, and mAP@0.50 of 60.1%, while YOLOv11x achieved a precision of 86.7%, recall of 65.3%, and mAP@0.50 of 61%. For rooster detection based on body size, YOLOv5xu, and YOLOv11m outperformed other variants, with YOLOv5xu achieving a precision of 88.9%, recall of 77.7%, and mAP@0.50 of 82.3%, while YOLOv11m achieved a precision of 89.0%, recall of 78.8%, and mAP@0.50 of 82.6%. This study provides a reference for automatic rooster monitoring based on comb and body size and offers further opportunities for tracking the activities of roosters in a poultry breeder farm for performance evaluation and genetic selection in the future. Full article

Stocking density is one of the major concerns in all production systems, which is why lawmakers, retailers, and consumers are increasingly concerned about this issue and its relation to animal welfare. The aim of this study was to identify if stocking density had an effect on white egg layer production, egg quality, bird health, and welfare parameters. For this study, five stocking densities were evaluated in colony cages: 1342 cm²/hen, 897 cm²/hen, 671 cm²/hen, 535 cm²/hen, and 445 cm²/hen. Egg production and physical egg quality were measured. Hen health and welfare parameters including corticosterone levels, H/L, oxidative stress pathways, jejunum tight junction protein expression, bone health, gut histology, body condition, and cytokine expression were evaluated. The results from this indicated that higher stocking densities resulted in lower production but larger eggs, while feed efficiency remained unaffected. Furthermore, physical egg quality parameters also remained unaffected. When stress and welfare parameters were analyzed, this research identified that decreasing stocking density did not affect jejunum oxidative stress pathways, pro-inflammatory cytokine expression, bone health, or intestinal health. At the final sampling period (69 weeks), the highest stocking density demonstrated higher corticosterone concentrations and IL-10 expression compared to the lowest stocking density. Furthermore, feather scores were found to be poorer as density increased. Finally, the highest density had higher Hansen’s test scores compared to other densities, which indicates a greater fear response. In conclusion, it appears that decreasing stocking density may provide some benefits in production and welfare to commercial egg layers, particularly at the end of the laying cycle. Full article

Limited published data areavailable on the current DLys requirements of Hy-Line Silver-Brown layers. The effects of energy (AMEn) and standardized ileal digestible lysine (DLys) concentration on the performance of Hy-Line Silver-Brown layers were studied from 20 to 35 weeks of age. The experimental design was randomized with twenty-four dietary treatments arranged as a 2 × 12 factorial with two AMEn concentrations (2750 and 2900 kcal/kg feed) and twelve levels of DLys (4.2, 4.5, 4.8, 5.1, 5.4, 5.7, 6.0, 6.6, 6.3, 6.9, 7.2, and 7.5 g/kg). Total egg weight (TEW), average egg weight, total egg number (TEN), laying rate, total feed intake, average daily feed intake (ADFI), mortality, hen body weight, hen body weight gain, eggshell thickness, eggshell breaking strength, yolk weight, albumen weight, and eggshell weight were recorded. An increase in energy content from 2750 to 2900 kcal AMEn/kg reduced ADFI (p < 0.001), egg mass output (p = 0.042), and feed conversion ratio (p = 0.018, g/g; p = 0.001, g/dozen) and increased the fat percentage in the liver (p = 0.028). An increased DLys intake from 529 to 882 mg/hen/day increased the TEN (p = 0.001), TEW (p < 0.001), and egg mass output (p < 0.001); improved the feed conversion ratio (p < 0.001); and reduced carcass (p = 0.001) and liver fat percentage (p = 0.05). Hy-Line Silver-Brown hens require no more than 780 mg (optimized egg production) and 880 mg (maximized egg weight) DLys/hen/day during pre-peak and peak production phases. Full article

We used an animal welfare-certified open-type layer farm and analyzed the egg production, egg quality, rectal temperature, and yolk corticosterone levels of laying hens supplied with cool water during the summer season (avg. 33 ± 3.89 °C). A total of 5750 Hy-Line Brown laying hens at 53 weeks of age were used, and two treatment groups were established: a control group (2900 hens) and a cool water treatment group (2850 hens). The water temperature of the control group was 25.3 ± 0.8 °C and the cool water was 20.1 ± 0.3 °C; all other environment parameters (lighting, ventilation, temperature, feed, etc.) were the same. The experiment was conducted for a total of 9 weeks (between July and September 2024), and during this period, the temperature–humidity index (THI) inside the breeding facility averaged 85.21, which corresponds to the cool water supply range (80 < THI < 90). As a result, the cool water treatment group maintained high productivity and showed low mortality (p < 0.05). In addition, hens provided with cool water showed high eggshell strength and low yolk corticosterone levels (p < 0.05). The core finding of this study is that the supply of cool water in summer is effective in maintaining the productivity and egg quality of laying hens and reducing HS. This is significant in that it suggests it is possible to manage laying hens in summer in a simple way, and it can also be used as basic data for designing future studies, such as using a combination of natural products including vitamins and minerals. Full article

To evaluate the influences of dietary Bacillus-based probiotics and yeast-based prebiotics over 16 weeks, 500 37-week-old Hisex white layers were indiscriminately assigned to five dietary groups: T1, control; T2, control + Bacillus subtilis (1.1 × 10⁸ CFU/kg); T3, control + Bacillus subtilis and Bacillus licheniformis (1.3 × 10⁹ CFU/kg); T4, control + Bacillus coagulans (1.0 × 10⁹ CFU/kg); and T5, control + Saccharomyces cerevisiae yeast cell wall (0.25 g/kg). Cumulatively (p < 0.001), T1 showed the highest feed consumption, while T4 and T5 had higher egg production than T1 and T3. T3 yielded the heaviest eggs, whereas T2 produced the lightest. Egg mass was higher in T3, T4, and T5, with all supplemented groups showing improved feed conversion ratios compared to the control. Furthermore, T5 showed a higher wet yolk weight (p < 0.001), while T2 and T5 had a higher dry albumin weight (p < 0.05). Additionally, T3, T4, and T5 reduced serum IL-1β (p < 0.05), IL-6 (p < 0.01), and TNF-α (p < 0.01), alongside elevated IL-10 levels (p < 0.01) relative to the control. Overall, the results suggest that dietary supplementation with multi-strain combinations and yeast-derived prebiotics can enhance both productivity and immune health in laying hens. Full article

Trehalose, a disaccharide consisting of two D-glucose molecules, is present in a variety of organisms, including bacteria, yeast, fungi, insects, and plants. In plants, it functions as a source of energy and carbon, and in yeast and plants, it serves as a signaling molecule, influencing metabolic pathways and growth regulation. Additionally, it plays a role in protecting proteins and cell membranes from stress-induced damage. This study aims to assess the optimal level of trehalose supplementation in the diets of layer hens aged 34 to 49 weeks, addressing the limited existing literature on its effects on productivity. Experimental diets, designed in accordance with nutritional recommendations, were formulated to contain six different levels of trehalose (0, 0.05, 0.10, 0.30, 0.60, and 1.00%). The study was conducted over five 21-day periods, during which various performance parameters were evaluated. The results indicated that trehalose supplementation at levels of 0.05%, 0.10%, and 0.30% led to increased feed intake (FI) compared to the 1.00% level (p < 0.05). Furthermore, the highest trehalose level (1.00%) significantly reduced the feed conversion ratio by egg mass (FCRem) compared to both the control group and the other supplementation levels; however, the feed conversion ratio by dry matter (FCRDz) remained consistent across all treatments. The levels of 0.05%, 0.10%, and 0.30% exhibited superior FCREm and FCRDz compared to the 1.00% level. Egg weight (EW) was higher in the trehalose-supplemented groups compared to the control group. Additionally, the 1.00% trehalose treatment was found to be the most effective in terms of relative weights of shells (RWS), and egg mass (EM) was higher at all trehalose levels compared to the control group. The antioxidant status, as measured by malondialdehyde (MDA) levels, indicated that supplementation with 0.30% and 0.60% trehalose had a protective effect against oxidative stress, although the 1.00% level resulted in increased MDA levels. Total weight (TW) was highest in the 0.30% treatment group, and bone strength (BS) improved in the groups supplemented with 0.10% and 1.00% trehalose. Other parameters, including lipid content (L), dry matter (DM), phosphorus (P), and calcium (Ca), did not show any significant differences among the treatment groups. In conclusion, supplementation with 1.00% trehalose enhances feed efficiency, egg weight, and quality, with minimal impact on lipid peroxidation, while potentially providing benefits for gut health and egg quality. Full article

This research aimed to assess body weight (BW) at the end of the brooding period in affecting Hyline Brown laying hens aged 6 to 72 wks from the aspects of growth performance, egg quality, sexual maturity, and productive performance. Pullets (6 wk old, n = 640) were sorted into two groups according to BW: normal (460.75 ± 10.82 g) and light (347.96 ± 6.27 g, 75.52% of normal weight), with eight replicates of 40 pullets each. All the hens, when reaching 6–72 wks in age, took the same diets by stages ad libitum. The heavier BW in the normal weight group (NWG) at 6 wks of age compared to lighter weight group (LWG) birds continued until 22 wks (p < 0.05). Similarly, a smaller coefficient of variation (CV) for BW of chicks in the LWG was detected at 19 (p < 0.01), 20 (p < 0.01), and 21 (p < 0.05) wks of age compared with that in the NWG. The body slope length and the shank circumference of pullets in the LWG were smaller than in the NWG at the age of 15 wks (p < 0.01), but the difference gradually disappeared by 20 wks of age (p > 0.05). The LWG presented raised ages of hens when producing the first egg and 5% eggs (p < 0.01), while the CV for the age at first egg decreased, compared with the CV in the NWG (p < 0.05). The total egg number (p < 0.05), laying rate (p < 0.05), and egg mass (p < 0.01) of laying hens in the LWG decreased at the age of 18–72 wks, and the CV for individual egg numbers (p < 0.05) increased compared with the CV in the NWG. Compared with the normal weight hens, the proportion of lighter weight hens laying more than 250 eggs at the age of 18–72 wks was significantly reduced (p < 0.05, 69.52% vs. 87.38%), while the proportion of hens laying less than 200 eggs was significantly increased (p < 0.05, 24.97% vs. 3.76%). In summary, BW by the end of the brooding period can be a good indicator reflecting individual differences among laying hens and may serve as an important phenotypic indicator for evaluating laying performance and early elimination of unqualified laying hens in layer production. Therefore, it is recommended that pullets weighing 25% or more below the normal flock weight at the end of the brooding period should be culled at this time. Full article

This study evaluates the effects of dietary selenium (Se) sources—sodium selenite (SS), nano-selenium (Nano-Se), selenocysteine (Se-C), and selenomethionine (Se-Met)—on production performance, egg quality, preservation characteristics, yolk Se content, and antioxidant capacity in Hy-Line Grey laying hens. A total of 450 healthy 18-week-old Hy-Line Grey laying hens were allocated to five groups (basal diet without Se, 0.30 mg/kg SS, Nano-Se, Se-C, or Se-Met) for an 8-week trial after a 4-week Se-depletion phase. The key results demonstrate that while no significant differences were observed in the feed intake, egg production rate, or egg weight among the groups (p > 0.05), organic Se (Se-C, Se-Met) and Nano-Se significantly improved the yolk color (p < 0.05) and yolk index (p < 0.05) and mitigated declines in the albumen height and Haugh unit during storage. Notably, Nano-Se exhibited superior efficacy in enhancing yolk color and antioxidant enzyme activity (p < 0.05). Furthermore, organic Se and Nano-Se increased yolk Se deposition (p < 0.05), increased yolk antioxidant enzyme activity (p < 0.05), and reduced lipid peroxidation (p < 0.05). These findings indicate that supplementing 0.3 mg/kg organic Se or Nano-Se enhances egg quality, extends shelf life, and improves antioxidant capacity, offering a sustainable strategy for selenium-enriched egg production. Full article

Regenerative, pasture-raised layer hen systems create synergistic relationships between the hens, forage, soil, and weather, fostering a sustainable system. However, the influence of these factors on egg nutrient profile and quality may vary by region. This study took place over two years; samples were collected from a farm in Ohio during the first year and a farm in Indiana during the second year. Egg (n = 12) and forage (n = 3) samples were collected monthly from September to December. Fatty acids were quantified using gas chromatography-mass spectrometry, micronutrients were assessed in a commercial laboratory, and carotenoids and polyphenols were analyzed colorimetrically. Ohio eggs had significantly darker yolks (average yolk fan score: 8.5 ± 1.8 vs. 3.9 ± 2.0; p < 0.0001), a higher beta carotene and carotenoid content, and a lower n-6:n-3 fatty acid ratio across the season. Indiana eggs had a lower average total phenolic content (0.07 ± 0.00 mg GAE/g vs. 0.14 ± 0.10 mg GAE/g) and lower average total cholesterol (5.35 ± 2.9 mg/g vs. 10.99 ± 1.54 mg/g). Forage composition and soil parameters varied between farms. Regional variations in forage composition, soil nutrients, and regional weather can significantly influence the nutrient density of eggs produced in sustainable, pasture-raising systems. This research highlights how local environmental factors can shape the nutritional profiles of eggs in different regions. Future studies should explore this relationship in more regions. Full article

This study aimed to investigate the effects of different supplemental amounts of dandelion flavonoid extracts (DFE) in diets on nutrients in chicken, slaughtering performance, blood biochemical indexes and antioxidant capacity of spent laying hens. A total of 180 560-day-old spent Hy-Line Brown laying hens were randomly divided into five groups. The control group was fed the basal diet, while the experimental groups were supplemented with DFE at levels of 1000, 2000, 4000, and 8000 mg/kg (as T1, T2, T3, and T4 group) in the basal diet, respectively. The variables measured included the content of dandelion flavonoids in layer hen thigh meat and breast meat, slaughter performance, blood biochemical indexes, and antioxidant capacity. Data were subjected to a one-way analysis of variance (one-way ANOVA) to assess the impact of DFE supplementation compared to the control group on study outcomes. The results showed that dietary supplementation with DFE can increase the content of dandelion flavonoids in layer hen meat. The contents of rutin in layer hen breast meat of groups T1, T2, T3, and T4 were 1.37, 4.41, 16.26, and 36.03 ng/g, respectively, and the contents of quercetin was 2.58, 1.36, 4.98, 12.48 ng/g. In layer hen thigh meat of groups T1, T2, T3, and T4, the contents of rutin were 11.48, 15.98, 44.43, 122.32 ng/g, and the contents of quercetin were 9.96, 13.14, 23.15, 38.09 ng/g, respectively. The addition of DFE increased the total phenol content of the feed and highly significantly elevated the total phenol content of layer hen meat (p < 0.01), and the total phenol content of chicken meat was strongly and positively correlated with the total phenol content of the feed. DFE supplementation significantly decreased abdominal fat percentage (p < 0.05) and increased crude fat content in chicken (p < 0.05). The addition of DFE reduced aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities (p < 0.05), decreased triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL) cholesterol (LDL-C), glucose (GLU), and malondialdehyde (MDA) contents (p < 0.05), and increased the content of albumin (ALB), total antioxidant (T-AOC) capacity and total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px) activity (p < 0.05). Dietary supplementation of DFE at different concentrations could significantly increase the content of dandelion flavonoids in the muscle of spent laying hens, reduce the abdominal fat rate in hens, effectively reduce blood lipid levels, effectively increase crude fat content in thigh muscle, and enhance the body’s antioxidant capacity and liver function. Full article

Laying hens’ metabolism goes through a cyclic process to produce eggs, which requires higher dietary protein and energy in the morning (AM) and higher calcium (Ca) in the afternoon/evening (PM) than the rest of the day. Therefore, poultry scientists are trying to adopt a new feeding strategy called AM/PM or split feeding to precisely meet hen’s requirements more effectively than conventional methods. A 10-week cage layer trial was carried out via a Box–Behnken response surface design to identify the optimal amount of protein, energy, and calcium of the AM/PM diets. There were 13 test treatments with three levels of crude protein (19.6%/18.4%, 20.3%/17.7%, 21%/17%), calcium (3.3%/4.9%, 2.5%/5.7%, 1.6%/6.6%), and apparent metabolizable energy (AME) (12 MJ/kg/11.2 MJ/kg, 12.4 MJ/kg/10.8 MJ/kg, 12.8 MJ/kg/10.4 MJ/kg) for AM/PM diets respectively and a control treatment with industry baseline (CP-19%, Ca-4.1% and ME 11.6 MJ/kg). These are the calculated values of nutrients on a dry matter basis. A total of 364 hens were randomly distributed into 2 dietary treatments where each treatment had 13 replicates (2 hens per replicate cage, 26 hens per treatment). AM and PM diets were swapped out at approximately 8 am and 4 pm each day. Egg production and hen performance were measured daily and weekly, respectively, with egg quality, serum Ca, and nutrient digestibility measured at week 10. AM:PM intake and feed cost were calculated for each treatment. The optimal FCR, feed cost, and AM:PM intake were used to determine Ca, CP, and AME levels. The result showed that 6 out of 13 of our test treatments gave improved FCR compared to the control treatment (p = 0.017). Dietary treatments did not affect overall hen weight and serum Ca and egg quality at week 10, except for the lower yolk color score in the control treatment (p = 0.002). Hens in the experimental treatment, with calcium levels of 1.6% and 6.6%, crude protein (CP) levels of 19.6% and 18.4%, and AME content of 12.4 MJ/kg and 10.8 MJ/kg in the AM and PM diet, respectively, showed the highest apparent protein digestibility (56.6%) compared to the control group (p < 0.05). Similarly, hens receiving a treatment containing calcium at 3.3% and 4.9%, CP at 21% and 17%, and AME at 12.4 MJ/kg and 10.8 MJ/kg in the AM and PM diet, respectively, achieved the highest calcium digestibility (62.13%), while the control treatment yielded the lowest calcium digestibility (p < 0.05). After analyzing the data using the Box–Behnken response surface methodology, we found that (21/17)% CP, (3.3/4.9)% Ca, and (12/11.12) MJ/kg energy in the AM/PM diet gave the optimum performance in terms of lower feed cost and better feed efficiency. The data of AM:PM intake demonstrate that selective feeding occurs in between treatments (p < 0.001) and the degree of selection depends on the difference between the level of nutrients in AM and PM diet. This study revealed that when optimized, AM/PM feeding improves feed efficiency and egg quality of laying hens. Full article

A social network is a group of individuals forming a non-random social structure where the number of interactions systematically vary among individuals. The Red Junglefowl, the ancestor of all domesticated chickens, has been shown to form social structures within a larger group; however, how poultry in egg production are socially organised is poorly understood. Egg layers in groups of thousands of individuals are suggested to either, just as Red Junglefowl, form subgroups or to lose social affiliations and replace these with a system of social tolerance. In this case study, a stable group of 20 laying hens with known genetic relationships housed in an outdoor aviary were observed for 3 h per day, during 20 days, in order to determine the social structure in the group. Social affiliations and centralisation measurements were assessed by proximity. The results show that some individuals were consistently more centralised compared to others, which indicates a stable individual variation in sociality. Furthermore, no individual spent more than 10% of her total number of interactions with a particular individual, i.e., little consistency in social affiliations could be found. The results of this case study support the theory of a higher social tolerance rather than a consistent social organisation in domesticated egg layers. Full article

This research evaluated the impact of incorporating dried olive pulp (OP) into the feed of laying hens on the fatty acid profile, cholesterol, triglyceride, total phenolic, oleuropein and hydroxytyrosol content, and health lipid indices of eggs produced by mid- (39 weeks) and late-laying (59 weeks) birds. Over a 36-week trial, 300 eggs from 180 Isa-Brown hens, assigned to three dietary groups with different OP levels (CON, OP4 and OP6), were analyzed. OP reduced egg cholesterol, with significant effects in late-age eggs (p < 0.05). In mid-age hens, the OP6 eggs had higher total phenolics than the controls (p < 0.05) and more PUFAs than the other groups (p < 0.05). The concentration of total phenolics, cholesterol, n3 PUFAs and % fat increased with hen age (p < 0.05), while triglycerides and oleuropein decreased (p < 0.05). With increasing hen age, the SFAs in the OP eggs decreased (p < 0.05) and the MUFAs increased (p < 0.05). Eggs from older hens had higher nutritional value, as indicated by the lower n6/n3 PUFA ratio, lower AI and TI indices, and higher h/H ratio (p < 0.05). Overall, dietary OP supplementation improved the nutritional quality of eggs, suggesting potential health benefits. Our results also highlighted eggs from older hens as a valuable source of high-quality fats. Full article

The eggshell quality traits in avian species, including Yunnong chickens (YN), are crucial for commercial and breeding purposes. The use of advanced biotechnologies, such as gene sequencing, has become increasingly common for identifying genetic markers and comparing specific traits in livestock. However, genetic markers related to eggshell traits in YN chickens remain unexplored. This study aimed to compare eggshell quality traits and identify genetic markers in YN chickens versus commercial Jingfen chickens (JF). A total of 400 chicks (200 per breed) were reared for 300 days under controlled conditions. At the end, 60 eggs from each breed were analyzed using scanning electron microscopy to examine eggshell cross-sections and mammillary layer structure. Tissue samples from kidneys and eggshell glands were collected from six hens per breed for RT-qPCR analysis to study gene expression profiles. Results showed that YN chickens had significantly higher eggshell strength, thickness, mammillary density, and effective layer thickness than JF chickens (p < 0.01). Despite this, YN chickens had a thinner mammillary layer. RT-qPCR analysis confirmed five candidate genes related to eggshells (LSS, NSDHL, MSMO1, SQLE, and FDFT1) that play an important role in this process. Pathway analysis revealed significant enrichment in several biological processes, including steroid biosynthesis, glycerolipid metabolism, purine metabolism, and thiamine metabolism. Based on these results, the YN chickens have strong eggshells with better thickness, mammillary density, and effective layer thickness. In addition, genomic and pathways analysis suggest a complex interaction of metabolic, immune, and cellular processes potentially influencing eggshell quality traits in poultry. Full article