Blood biochemistry and immune response in Aseel chicken under free range, semi-intensive, and confinement rearing systems

Identification of Metabolites in Muscles of Lueyang Black-Bone Chickens: A Comparative Analysis of Caged and Cage-Free Rearing Modes Using Untargeted Metabolomic Techniques

The Lueyang black-bone chicken is a specific native chicken strain in China. This study aimed to investigate the effects of different rearing systems on the meat quality of Lueyang black-bone chickens. Six hundred Lueyang black-bone hens were randomly divided into two groups at 7 weeks of age and raised in cage and cage-free systems for 20 weeks. The carcass yield, meat quality, and total metabolites were measured in both the leg and breast muscles. By comparison, the carcass yield of hens in the cage-free (CF) group (1.26 ± 0.09 kg) was significantly lower than that in the caged rearing (CR) group (1.52 ± 0.15 kg). However, the shear force of leg muscles in the CF group (27.98 ± 2.43 N) was significantly greater than that in the CR group (24.15 ± 1.93 N). In addition, six samples from each group were randomly selected and their metabolites were detected by the non-targeted metabolomics technique. Among these metabolites, 408 and 354 significantly differentially abundant metabolites were identified in breast and leg muscles, which were mainly involved in glycerophospholipid metabolism, unsaturated fatty acid biosynthesis, arginine and proline metabolism, and nucleotide metabolism. We found that the levels of 19 phospholipids, mainly phosphatidylcholines and lysophosphatidylcholines, were significantly greater in the CF group than in the CR group. Additionally, the contents of eight unsaturated fatty acids, linoleic acid, and linolenic acid were dramatically greater in the CF group than in the caged group. The accumulation of 4-hydroxy-proline, glutamate, and adenosine 3'-monophosphate (AMP) was enhanced in the CF group. Moreover, many more volatile organic compounds were identified in the muscles of the cage-free group, enhancing the flavor of the chicken meat. In conclusion, the cage-free rearing mode facilitates the accumulation of nutrients and flavor substances in the chicken meat and is a better rearing system for Lueyang black-bone chickens.

Effects and Mechanisms of Cage versus Floor Rearing System on Goose Growth Performance and Immune Status

Currently, FRS and CRS are the two predominant dryland rearing systems in the goose industry. However, the effects of these two systems on goose growth performance and health, as well as the underlying mechanisms, have not been fully clarified. Thus, this study aimed to compare growth performance and immune status, as well as investigate the genome-wide transcriptomic profiles of spleen in geese, between CRS and FRS at 270 d of age. Phenotypically, the body weight and body size traits were higher in geese under FRS, while the weight and organ index of spleen were higher in geese under CRS (p < 0.05). Noticeably, the bursa of Fabricius of geese under FRS was degenerated, while that under CRS was retained. At the serum level, the immune globulin-G (IgG) and interleukin-6 (IL-6) levels were higher in geese under CRS (p < 0.05). At the transcriptomic level, we identified 251 differentially expressed genes (DEGs) in the spleen between CRS and FRS, which were mainly enriched in scavenger receptor activity, inflammatory response, immune response, neuroactive ligand-receptor interaction, phenylalanine metabolism, ECM receptor interaction, calcium signaling pathway, phenylalanine, tyrosine, and tryptophan biosynthesis, regulation of actin cytoskeleton, and MAPK signaling pathways. Furthermore, through protein-protein interaction (PPI) network analysis, ten candidate genes were identified, namely, VEGFA, FGF2, NGF, GPC1, NKX2-5, FGFR1, FGF1, MEIS1, CD36, and PAH. Further analysis demonstrated that geese in CRS could improve their immune ability through the "phenylalanine metabolism" pathway. Our results revealed that the FRS improved growth performance, whereas the CRS improved goose immune function by increasing levels of IL-6 and IgG in serum. Moreover, the phenylalanine metabolism pathway could exert positive effects on immune function of geese under CRS. These results can provide reliable references for understanding how floor and cage rearing systems affect goose growth performance and immune capacity.

Effects of selenium supplementation on the growth performance, slaughter characteristics, and blood biochemistry of naked neck chicken

This study examined how selenium-supplemented diets affected the performance of naked neck chickens. The birds were fed both organic and inorganic selenium at 0.30 ppm, while the control diet did not include any additional selenium. A total of 225 one-day-old naked neck chicks were randomly divided into 3 experimental groups, each of which was replicated 5 times (replicates) and contained 15 birds. This was done using a completely randomized design. The data was collected after growth, meat quality, and blood profile parameters were assessed. The findings showed that the birds fed inorganic selenium in the diet displayed increased (P < 0.05) feed intake followed by those administered organic selenium and the control diet. On the other hand, birds fed organic selenium in the diet showed enhanced body weight gain and better feed conversion ratio (P < 0.05). Similarly, organic selenium supplementation increased (P < 0.05) breast and thigh weight compared to inorganic selenium, but no other metrics, such as dressing percentage, drumstick weight, liver weight, gizzard weight, heart weight, or wing weight, significantly differed between treatments (P > 0.05). When compared to birds fed inorganic Se and control diet, the birds fed organic Se had greater (P < 0.05) blood levels of total protein and globulin. Additionally, it was discovered that organic Se-fed birds had greater (P < 0.05) blood Se concentrations than control and inorganic Se-fed birds. However, no differences between treatments were found in albumin, glucose, cholesterol, triglycerides, or uric acid (P > 0.05). In conclusion, adding Se-enriched yeast, as an organic selenium source, to diets may enhance the poor growth and slaughter characteristics of naked neck chicks without negatively affecting blood chemistry.

Valgus-varus deformity induced abnormal tissue metabolism, inflammatory damage and apoptosis in broilers

1. This study explored the tissue metabolic status and the relationship with inflammation in valgus-valgus deformity (VVD) broilers with increasing age.2. Tissue and blood from VVD and healthy broilers were collected at two, four and five weeks old. A fully automated biochemical analyser, real-time PCR, HE staining and enzyme-linked immunosorbent assay were used to detect tissue metabolic indexes, mRNA levels of inflammation and apoptosis cytokines in immune organs, histological changes and serum inflammation and immune-related protein contents in VVD broilers.3. The results showed that VVD increased the levels of total protein, albumin, alanine aminotransferase at five weeks of age, aspartate aminotransferase, urea and creatine kinase in blood at two weeks of age. It upregulated the gene expression of inflammatory factors IL-1β, IL-6, IL-8, TNF-α, NF-κB and TGF-β and apoptotic factors FAS, Bcl-2, caspase-3 and 9 in immune organs; increased levels of serum proteins TNF-α, IL-1β and IL-6 and decreased levels of serum immunoglobulins IgY and CD3⁺.4. In addition, with increasing age, IL-10 gene expression gradually increased in the BF and decreased in the spleen.5. In conclusion, VVD broilers have disorders of liver and kidney metabolism, inflammation and apoptosis of immune organs and increased levels of serum inflammatory factor proteins.

Effects of rearing system and antibiotic treatment on immune function, gut microbiota and metabolites of broiler chickens

BACKGROUND

In China, cage systems with a high space utilization have gradually replaced ground litter systems, but the disease incidence of chickens in cages is higher. Broilers in the ground litter pens may be stimulated by more environmental microbes during the growth process and show strong immune function and status, but knowledge of which microbes and their metabolites play an immunomodulatory role is still limited. This study aimed to explore the differences and correlations in the immune function, gut microbiota and metabolites and the importance of gut microbiota of broilers raised in cages and ground litter pens.

METHODS

The experiment involved a 2 × 2 factorial arrangement, with rearing systems (cages or ground litter pens) and antibiotic treatment (with or without broad-spectrum antibiotics in drinking water) as factors.

RESULTS

The results showed that, compared with the cage group, the ground litter broilers had stronger nonspecific immune function (Macrophages% and NO in blood), humoral immune function (IgG in blood, LPS stimulation index in ileum) and cellular immune function (T%, Tc%, ConA stimulation index and cytokines in blood). Antibiotic (ABX) treatment significantly reduced nonspecific immune function (Macrophages% and NO in blood, iNOS and Mucin2 mRNA expression in ileum), humoral immune function (IgG in blood and sIgA in ileum) and cellular immune function (T% and cytokines in blood, Th and Tc ratio, TLRs and cytokines mRNA expression in ileum). Furthermore, the ground litter broilers had higher α diversity of microbiota in ileum. The relative abundance of Staphylococcus, Jeotgalicoccus, Jeotgalibaca and Pediococcus in the ileum of ground litter broilers were higher. ABX treatment significantly reduced the α diversity of ileal microbiota, with less Chloroplast and Mitochondria. In addition, the levels of acetic acid, isobutyric acid, kynurenic acid and allolithocholic acid in the ileum of ground litter broilers were higher. Spearman correlation analysis showed that Jeotgalibaca, Pediococcus, acetic acid, kynurenic acid and allolithocholic acid were related to the immune function.

CONCLUSIONS

There were more potential pathogens, litter breeding bacteria, short-chain fatty acids, kynurenine, allolithocholic acid and tryptophan metabolites in the ileum of broilers in ground litter pens, which may be the reason for its stronger immune function and status.

Comparison and Correlation Analysis of Immune Function and Gut Microbiota of Broiler Chickens Raised in Double-Layer Cages and Litter Floor Pens

This study aimed to compare the immune function and gut microbiota between double-layer caged and litter floor pen-raised broiler chickens. Eighty meaty male chicks were selected and divided into cage group and litter floor group, with 20 replicates in each group. The broilers were raised in the same chicken house. The rearing density of the two rearing systems was same. The broilers were sampled on days 13 and 34. The results showed that compared with the cage group, the litter floor broilers had worse growth performance (23.24% increase in feed conversion ratio) in the early stage; better slaughter performance at day 42; stronger peripheral immune function (including higher lysozyme activity, T-cell ratio, Th-cell ratio, Tc-cell ratio, CD4/CD8, IL-10, B-cell ratio, IgG and IgA levels; and spleen immune-related gene expression); and stronger intestinal immune function (including higher ileum CD80, AvBD2, Mucin2, NF-κB, IL-8, IFN-γ/IL-4, and IgA mRNA expression levels and ileal mucosa sIgA levels). Compared with the cage group, the alpha diversity of ileum microbiota of the litter floor broilers was higher, and the relative abundance levels of litter breeding bacteria (Facklamia, Globicatella, and Jeotgalicoccus) and potential pathogenic bacteria (Streptococcus and Staphylococcus) were higher (P < 0.05). Through Spearman correlation analysis, it was found that enriched microbes in the ileum of litter floor broilers were positively correlated with immune function. In summary, compared with cage broilers, litter floor broilers had more potential pathogenic bacteria and litter breeding bacteria in the ileum, which may be one of the important reasons for the stronger immune function status. IMPORTANCE In China, the three-dimensional rearing system (cage) for broilers has gradually become a trend. In production, it was found that the incidence of disease in broiler chickens raised in cage systems was significantly higher than that of ground litter. Given that broilers raised on ground litter systems may be exposed to more environmental microbes, it is important to understand whether the rearing environment affects the function and status of the host immune system by altering the gut microbiota. In this study, rearing environment-derived gut microbes associated with stronger immune function in ground litter broilers were provided, which will provide new insights into strategies to target gut microbes to promote immune function and status in broilers raised in cages.

The Welfare Status of Hens in Different Housing Systems – A Review

The currently used poultry farming methods, which aim to maximise economic profit, are based on ever new technological solutions that improve flock management and increase bird performance. However, they do not always meet the natural needs of birds. Every housing method and technological solution currently in use is faced with some issues, such as social stress, adverse temperature/ humidity conditions, risk of zoonoses, and behavioural pathologies, which determine poultry performance and welfare. Disregard for animal welfare involves not only ethical but also practical aspects, because well-being and housing comfort translate into better weight gains, health and productivity of the birds. The studies reported here suggest that every production system, despite the many welfare-improving aspects, causes numerous behavioural, productivity and health abnormalities in laying hens. Therefore, further research is needed to identify various risk factors for the purpose of improving housing systems and increasing the welfare of hens.

Effects of Dietary Ferulic Acid on the Intestinal Microbiota and the Associated Changes on the Growth Performance, Serum Cytokine Profile, and Intestinal Morphology in Ducks

The present study investigated the effects of ferulic acid (FA) on the growth performance, serum cytokine profile, intestinal morphology, and intestinal microbiota in ducks at the growing stage. 300 female Linwu ducks at 28 days of age with similar body weights were randomly divided into five groups. Each group contained six replicates of 10 birds. The dietary treatments were corn-soybean-based diet supplemented with FA at the concentrations of 0 (control), 100, 200, 400, and 800 mg/kg diet. The results demonstrated that dietary FA at the levels of 200, 400, and 800 mg/kg increased the average daily gain (P = 0.01), 400 and 800 mg/kg FA increased the final body weight (P = 0.02), 100, 200, and 800 mg/kg FA increased the serum glutathione (P = 0.01), and 100, 400, and 800 mg/kg FA increased the glutathione peroxidase activities in birds (P < 0.01). Additionally, 200, 400, and 800 mg/kg dietary FA lowered the serum levels of interleukin-2 (P = 0.02) and interleukin-6 (P = 0.04). Moreover, the morphometric study of the intestines indicated that 400 mg/kg FA decreased the crypt depth in jejunum (P = 0.01) and caecum (P = 0.04), and increased the ratio of villus height to crypt depth in jejunum (P = 0.02). Significant linear and/or quadratic relationships were found between FA concentration and the measured parameters. 16S rRNA sequencing revealed that dietary FA increased the populations of genera Faecalibacterium, Paludicola, RF39, and Faecalicoccus in the cecum (P < 0.05), whereas decreased the populations of Anaerofilum and UCG-002 (P < 0.05). The Spearman correlation analysis indicated that phylum Proteobacteria were negatively, but order Oscillospirales, and family Ruminococcaceae were positively related to the parameters of the growth performance. Phylum Bacteroidetes, class Negativicutes and family Rikenellaceae were negatively associated with the parameters of the antioxidative capability. And phylum Cyanobacteria, Elusimicrobia, and Bacteroidetes, class Bacilli, family Rikenellaceae, and genus Prevotella were positively associated with the parameters of the immunological capability. Thus, it was concluded that the supplementations of 400 mg/kg FA in diet was able to improve the growth performance, antioxidative and immunological capabilities, intestinal morphology, and modulated the gut microbial construction of Linwu ducks at the growing stage.

Effects of rearing systems on production performance, antioxidant capacity and immune status of meat ducks at different ages

As potential substitutes for traditional free-range rearing system, floor-rearing system (FRS) and net-rearing system (NRS) are the current predominant dryland duck rearing systems. However, the influence of these two systems on production performance and duck health is poorly understood. In this study, a 2 × 3 factorial arrangement with two rearing systems (FRS and NRS) and three ages (4w, 8w and 13w) was conducted to study the effects of FRS and NRS on production, antioxidant capacity and immune status of Nonghua ducks. The production performance was mainly affected by the effect of rearing systems at 8w. Body weight, average daily gain, eviscerated weight and semi-eviscerated weight were higher in NRS ducks at 8w, but carcass yield at 8w and 13w was decreased (P < 0.05). Lipid deposition was enhanced in NRS and higher sebum and abdominal fat yields were seen at 8w and 13w (P < 0.05). NRS resulted in developmental retardation of the liver at 4w and decreased gizzard index at all ages (P < 0.05). Antioxidant capacity indicators were unaffected by rearing systems (P > 0.05), however, in NRS, slightly better antioxidant capacity was seen at 4w, while glutathione peroxidase (GSH-Px) activity was higher at 13w (P < 0.05). NRS ducks had higher thymus weight at 8w and higher spleen weight at 13w (P < 0.05). Immune cytokines were extensively affected by rearing system (P < 0.05) and higher levels of interferon-γ, interleukin-1β, interleukin-4 and immunoglobulins were seen in NRS ducks. Serum biochemical parameters (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP)) showed that NRS was better for liver health, and in the liver of FRS ducks, ALP was higher at 13w, and both ALP and interferon-γ were higher at 13w than at 4w and 8w (P < 0.05). In conclusion, this study showed that NRS was, to an extent, conducive to production performance and duck liver health, but compared to FRS, defects were seen in visceral organ development and lipid deposition. Although antioxidant capacity was not significantly affected, NRS ducks may have better antioxidant capacity at the early breeding stage, and GSH-Px activity was increased for scavenging excess free radicals at the later one. NRS increased serum levels of interferon-γ, interleukin-1β, interleukin-4 and immunoglobulins and promoted thymus and spleen development, thus improving duck immune function. These findings will provide a reliable reference for selecting a rearing system.

Impact of Housing Environment on the Immune System in Chickens: A Review

During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual's allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.

Influence of free-range days on growth performance, carcass traits, meat quality, lymphoid organ indices, and blood biochemistry of Wannan Yellow chickens

This study investigated the effects of free-range days on growth performance, carcass traits, meat quality, lymphoid organ indices, and blood biochemical parameters of Wannan Yellow chickens. A total of 1,000 one-day-old male Wannan Yellow chickens were reared to 56 D. At 56 D of age, 960 birds with similar body weight (BW) were randomly allocated to free-range treatment at 56, 70, 84, and 98 D of age (assigned to free-range treatment for 42, 28, 14, and 0 D, respectively); 6 replicates with 40 chickens per treatment. In the free-range system, chickens were reared in indoor floor pens with an outdoor free-range paddock measuring 4 × 7 m (28 m2, 1.5 birds/m2). Results showed that BW of birds decreased significantly in the first 2 wk after birds were assigned to free-range treatment compared with those in the conventional treatment (P < 0.05). Average daily gain (ADG) and average daily feed intake (ADFI) decreased significantly (P < 0.05) for chickens assigned to free-range treatment from 56 to 70 D of age, while feed conversion ratio increased significantly (P < 0.05). Breast yield increased linearly with increasing free-range days (P < 0.05), whereas leg and foot yields decreased linearly (P < 0.05). Drip loss and L* value of thigh muscle decreased linearly with increasing free-range days (P < 0.05), while shear force improved linearly (P < 0.05). Additionally, the absolute thymus weight and thymus to BW ratio showed significant increasing and then decreasing quadratic responses to increasing free-range days (P < 0.05). Furthermore, serum glucose, total protein, cholesterol, and triglyceride content declined linearly, while high-density lipoprotein cholesterol (HDL-C) content increased linearly with increasing free-range days (P < 0.05). In conclusion, increasing free-range days had positive effects on breast yield, shear force, thymus weight, and HDL-C content, but negatively affected leg yield, foot yield, drip loss, L* value of thigh muscle, glucose, total protein, cholesterol, and triglyceride levels of Wannan Yellow chickens.

Effects of cage size on growth performance, blood biochemistry, and antibody response in layer breeder males during rearing stage

This study was conducted to investigate the effects of cage size on growth performance, blood biochemistry, and antibody response in layer breeder males during rearing stage. 575 one-day-old Jinghong layer breeder males were randomly allocated into 3 treatments and reared in 3 cage sizes: large (160 × 160 × 62 cm; LC), medium (120 × 120 × 62 cm; MC), and small (80 × 70 × 62 cm; SC). The stocking density of birds in 3 treatments was kept identical and adjusted every 2 wk, from 45 birds/m2 during the period of 0 to 2 wk of age to 12 birds/m2 during the period of 17 to 18 wk of age. Body weight and shank length were measured every 2 wk, and then the daily weight gain and daily feed intake were calculated. Tibia length and breaking strength were determined at 8 wk of age. Blood parameters including malodiadehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), alkaline phosphatase (ALP) and corticosterone (CORT), and antibody titers against avian influenza viruses H5N1 (Re-5 strain) and H9N2 (Re-2 strain) and Newcastle disease virus in response to vaccination were determined at 18 wk of age, respectively. Body weight, shank length, and daily weight gain of birds in LC were similar with those in MC, and were greater than those in SC at 18 wk of age (P < 0.05), respectively. No significant difference was found in average daily feed intake among the 3 treatments from 11 to 18 wk of age. Birds in LC and MC had the similar tibia length; however, birds in SC were smaller (P < 0.05). Tibia breaking strength of birds in LC was higher than those in SC (P < 0.05), respectively. Birds in LC showed lower plasma MDA, GSH-Px, SOD, and CORT contents than those in MC and SC (P < 0.05); however, birds in LC exhibited higher levels of serum antibody titers against H5N1 and H9N2 avian influenza viruses as compared with MC and SC (P < 0.05). Consequently, LC and MC were superior to SC and were beneficial for birds' growth and development.

Effects of rearing systems on growth performance, carcass yield, meat quality, lymphoid organ indices, and serum biochemistry of Wannan Yellow chickens

This study was conducted to investigate the effects of free-range system (FRS) and conventional cage-rearing system (CRS) on growth performance, carcass yield, meat quality, lymphoid organ indices, and serum biochemistry of Wannan Yellow chickens. At 56 days of age, a total of 640 male chickens were randomly allocated to FRS and CRS groups, each of which included 4 replicates with 80 chickens in each replicate. The experiment lasted from 56 to 112 days of age. The results showed that CRS chickens exhibited better final body weight, average daily feed intake, average daily gain, and feed conversion ratio, whereas FRS chickens showed better breast and leg yields, shear force, meat color, lower drip loss, and decreased abdominal fat deposition. Moreover, the absolute thymus weight and thymus to body weight ratio of FRS birds were significantly higher than those of CRS birds (p < 0.05). Additionally, FRS chickens had significantly reduced glucose, total protein, triglyceride, and cholesterol contents, but enhanced levels of high-density lipoprotein cholesterol (p < 0.05). In conclusion, the FRS has advantages in breast and leg yields, meat quality, and some serum biochemical parameters of Wannan Yellow chickens, whereas it has negative effects on growth performance.

Effects of rearing systems on laying performance, egg quality, and serum biochemistry of Xianju chickens in summer

The objective of this study was to compare the laying performance, egg quality, and serum biochemistry of hens maintained in conventional cage rearing system (CRS), flat net-rearing system (NRS), and free range system (FRS) under summer conditions. Indigenous Xianju chickens (n = 540) were randomly allocated into cages or pens of rearing system groups, within each system there were 5 replicates with 36 hens in each replicate. The experiment lasted between 21 and 29 wk of age. Hen-day egg production (P = 0.00) and egg mass (P = 0.00) were higher in the CRS but were similar in the NRS and FRS. Lowest egg weight (P = 0.02), yolk weight (P = 0.00) and yolk ratio (P = 0.01), and feed intake (P = 0.01) were observed from the FRS, whereas lowest feed conversion ratio (FCR) was recorded from the CRS (P = 0.01). Rearing systems had negligible effect on egg quality. Serum Ca (P = 0.04) and total protein (P = 0.03) levels were found to be higher in the CRS but were lower in the FRS. Serum levels of glucose (P = 0.01), cholesterol (P = 0.00), and triglyceride (P = 0.00) in the CRS increased compared with the NRS and FRS groups, whereas serum levels of high density lipoprotein cholesterol (HDL-C; P = 0.01) in the CRS decreased. It can be concluded that under summer conditions, Xianju chickens from CRS had an advantage in terms of productivity parameters, but exhibited higher levels of serum lipids and glucose.

Effects of different rearing systems on growth performance, carcass traits, meat quality and serum biochemical parameters of Chaohu ducks

This study was conducted using a total of 360 22-day-old Chaohu ducks to evaluate the effect of rearing system on growth performance, carcass traits, meat quality and serum parameters of male and female Chaohu ducks. The birds were divided and raised in separate pens according to sex and rearing system, with three replicate pens of 30 male or 30 female ducks per pen for each rearing system. The rearing systems consisted of a floor rearing system (FRS) and a net rearing system (NRS). Results showed that ducks raised in NRS had better growth performance, whereas, ducks raised in FRS exhibited better carcass traits and meat color, and lower intramuscular fat. For the serum parameters, NRS significantly decreased high-density lipoprotein cholesterol content, and enhanced total protein and triacylglycerol contents. Male ducks had lower abdominal fat percentage, and higher growth performance and shear force, but there were no other significant differences between sexes. No rearing system × sex interaction was observed in the present study, revealing that rearing system had the same effect on both sexes. In conclusion, NRS was beneficial to the growth performance of Chaohu ducks, whereas this system had some negative effects on carcass traits, meat quality and serum profiles.