Eggs are increasingly recognized not only as nutrient-dense foods but also as sources of bioactive compounds with potential physiological relevance. Native chicken eggs, produced under diverse genetic backgrounds and often under low-input production systems, may exhibit compositional characteristics that differ from those of commercial layer eggs. This review summarizes the major bioactive compounds of native chicken eggs and critically evaluates the current evidence regarding their possible implications for human health. Yolk phospholipids and omega-3 fatty acids have been associated with pathways related to lipid metabolism and membrane function, whereas carotenoids such as lutein and zeaxanthin exhibit antioxidant properties and have been discussed in relation to visual function. Albumen proteins, including lysozyme, ovotransferrin, and ovomucoid, have demonstrated antimicrobial and immunomodulatory activities mainly in experimental settings. Some studies have reported that native chicken eggs contain higher levels of antioxidant micronutrients and distinctive lipid profiles compared with commercial eggs, although such differences are not consistent and may vary with breed, diet, and production systems. Overall, native chicken eggs represent a potentially valuable food resource beyond basic nutrition. However, current evidence for their proposed cardiometabolic, antioxidant, and immune-related effects is derived largely from compositional analyses and from in vitro or animal studies, with only limited evidence in humans. Future research integrating multi-omics approaches, standardized comparative designs, and well-controlled human studies is needed to assess whether the compositional and experimental findings reported for native chicken eggs translate into meaningful benefits in humans and to their development as value-added functional food products.

Objective: Domestication alters the phenotypes of wild animals to meet human demands and leaves characteristic patterns in their genomes. Various selection signature analysis methods have been developed to identify these characteristic patterns left in the genome. The Korean native duck (KND) is one of the domesticated species in Korea. KND is categorized into two populations based on plumage color; colored KND (KNDC) and white KND (KNDW). To enhance the competitiveness of native ducks, it is necessary to establish a KNDW line. In this study, we conducted selection signature analysis to identify candidate genes associated with white plumage color in KNDs. Methods: We generated whole genome resequencing data from 22 KNDCs, 22KNDWs, and 10 Pekin ducks (PKDs). To detect distinct genomic regions between KND populations with different plumage colors, we analyzed three types of selection signature analysis: the fixation index (Fst), nucleotide diversity(pi), and cross-population extended haplotype heterozygosity (XP-EHH). Results: Population structure analysis showed that although KNDC and KNDW are distinct from PKD, they form a single group sharing a common ancestor. The results of Fst and pi analyses revealed that compared to KNDC, there were strong selection signals in the MITF gene in KNDW, with a 6,641 bp insertion in the intron 2 region. This variant is a transposable element insertion that causes white plumage in PKD. In addition, XP-EHH analysis identified DCT, KIT, TYR, and ADCY9 as major candidate genes associated with pigmentation in the KND population. Conclusion: White plumage in KNDW is caused by a transposable element insertion in the MITF gene. This finding improves our understanding of plumage color in KND and supports the establishment of KNDW breeding programs.

OBJECTIVE:This study aimed to identify the optimal single nucleotide polymorphism (SNP) panel density for accurate imputation in the Korean native chicken (KNC) and Yeonsan Ogye (YO) populations. The primary focus was on evaluating how the reference population size and SNP density influence imputation performance and accuracy. METHODS:Data were collected from five purebred lines of KNC and the YO population, comprising a total of 256 KNC and 199 YO chickens. Imputed genotype ratio and accuracy were evaluated across various scenarios using SNP densities of 2.5K, 5K, 10K, and 50K in both populations. Additionally, for the YO dataset, reference population sizes of 50, 100, and 150 were analyzed to assess their impact on imputation outcomes. RESULTS:Higher SNP densities notably improved imputation performance. Specifically, when SNP panel density reached 10K or greater, the ratio of imputed SNPs exceeded 70% and the accuracy increased substantially, regardless of the reference population size. However, imputation efficiency decreased markedly when either the reference or test population size was around 50 individuals. CONCLUSION:A test SNP density of at least 10K was determined to be essential for accurate genotype imputation. Additionally, imputation efficiency was observed to decline when either the reference or test population included around 50 individuals. These findings provide important data that can guide the genetic improvement of indigenous livestock populations.

Improving the flavor of chicken meat while maintaining productivity has become an important goal in poultry breeding. This study investigated the genetic characteristics of 20 taste-active compounds (TACs) and carcass weight (CW) in the Korean native chicken red-brown line. The TACs encompassed a wide range of metabolites, including free amino acids, peptides, organic acids, and nucleotide-related compounds. Genetic parameters were estimated using data from 829 birds, applying a multi-trait genomic model. Most TACs showed moderate heritability. Among them, inosine and carnosine stood out with relatively high heritability estimates of 0.45 and 0.34, respectively, indicating strong potential for genetic improvement. Trait correlations reflected known metabolic relationships. For example, leucine and methionine were positively correlated with a coefficient of 0.68, while inosine and its metabolic precursor inosine-5-monophosphate (IMP) showed a strong negative correlation of 0.71, suggesting regulatory competition. In addition, several TACs demonstrated undesirable associations with CW. Acetate, in particular, had a phenotypic correlation of -0.44 with CW, implying that selection for flavor-related traits may affect growth performance if not properly balanced. These findings reveal that many flavor compounds are under moderate genetic control and have biologically meaningful interactions. Integrating these compounds into breeding objectives can help develop chickens with improved sensory qualities while maintaining acceptable production levels. This strategy supports a more consumer-oriented approach to native chicken breeding.

This study investigated the relationship of lipid-protein oxidation with meat quality and volatile organic compounds in breast meat of Korean Woorimatdag No. 2 chicken (WRMD2) and commercial broiler (CB) under vacuum storage at –20 °C for 270 days. Frozen storage significantly affects lipid-protein oxidation, quality, and volatile profiles of chicken meat. WRMD2 exhibited a significantly higher degree of lipid oxidation than CB, as indicated by high levels of peroxide value, 2-thiobarbituric acid reactive substances, and p-anisidine value. However, WRMD2 was less susceptible to protein oxidation than CB, as demonstrated by the results of volatile basic nitrogen, carbonyl, and sulfhydryl assays. Lipid-protein oxidation was highly correlated with several meat quality and volatility indicators, including drip loss, surface color, polyunsaturated fatty acids, and specific aldehydes and alcohols. Moreover, a total of 33 VOCs, including benzeneacetaldehyde, benzaldehyde, nonanal, and decanoic acid, contributed to the separation between CB and WRMD2 at each storage time point. Our findings provide preliminary insights into the biochemical changes that occur during frozen storage, potentially contributing to the regulation and optimization of the quality of native chicken meat products globally.

The fatty acid composition of meat, which affects both its quality and the consumer’s health, is a complex trait influenced by genetic and environmental factors. Identification of the genes influencing the fatty acid composition of meat is very important for the selection and breeding of chickens with desirable and healthier fatty acid profiles. The objective of this study was to identify functional candidate genes for fatty acid profiles of the breast meat of the Korean native chicken-red-brown line (KNC-R) through genome-wide association studies. We genotyped 382 KNC-R chickens (190 males, 192 females) using the Illumina chicken 60K single nucleotide polymorphism (SNP) chip (Illumina, San Diego, CA, USA), and association tests were performed by mixed linear model in the Genome-wide Complex Trait Analysis (GCTA) software, based on mixed linear model analysis-leave-one-chromosome-out (MLMA-LOCO). We detected one SNP each on chromosomes 2 (rs13667281), 10 (rs14011157), and 22 (rs10731996) that were significantly (p < 0.05) associated with nervonic (C24:1), linoleic (C18:2), and eicosadienoic (C20:2) acids, respectively. We found 13 protein-coding genes related to lipid metabolism, including IGF2BP3, GPNMB, NPY, OSBPL3, IL6, NR2F2, GPAT4, NKX6-3, ANK1, SFRP1, ERLIN2, STAR, and PPP1R3E. Interestingly, two candidate genes (GPNMB and SFRP1) were reported to regulate the expression of genes known to be involved in fatty acid synthesis, such as the FASN, ACACA, ACLY, ELOVL, and SCD genes. Identification of functional candidate genes for fatty acid profiles might facilitate the selection and breeding of chickens with desirable and healthier fatty acids.

We evaluated the quality, storage stability, and flavor-related compounds of breast meat from a novel Korean native chicken breed (Woorimatdag No. 2; WRMD2) and commercial broiler (CB) during seven days of aerobic cold storage. We found that pH and drip loss increased gradually during storage and WRMD2 exhibited a significantly lower pH and higher drip loss than CB. In both groups, aerobic plate counts, volatile basic nitrogen, and lipid oxidation levels increased, whereas creatine and dipeptide levels gradually decreased during storage. WRMD2 exhibited a significantly higher anserine content and lower carnosine-to-anserine ratio than CB. Flavor nucleotide content was influenced more by the storage period, whereas fatty acid composition was affected more by genetic differences. WRMD2 exhibited significantly higher levels of polyunsaturated fatty acids, especially C20:4n6 and C22:6n3, than CB. Interestingly, multivariate analysis highlighted several volatile compounds, including methyl salicylate (day 1), dodecanal (day 3), naphthalene (day 5), and 2,4-decadienal (day 7) as potential biomarkers to distinguish between WRMD2 and CB on each storage day. Correlation analysis identified five key meat quality traits, including drip loss, aerobic plate counts, and anserine that are strongly associated with flavor substances, such as inosine monophosphate, guanosine monophosphate, 1-octen-3-ol, and hexanal. These results offer insights into the distinctive meat quality and flavor compounds in WRMD2 during storage, providing fundamental data that could improve the management and quality of native chicken meat.

The conservation of native chicken breeds is essential for promoting sustainable farming practice and preserving local genetic resources. Herein, we investigated the physicochemical quality, antioxidant activity, and flavor-related compounds of egg yolk from three Korean native chicken (KNC) breeds, namely blue-shelled egg (BSE), Woorimatdag No. 1 and 2 chicken egg (WRMD1E and WRMD2E), and commercial egg (CE). The physicochemical characteristics of chicken eggs, such as Haugh unit, yolk color, and eggshell characteristics, along with yolk traits including moisture, crude fat, pH, and cholesterol levels, were found to vary depending on the species (p < 0.05). The yolk of WRMD2E and CE exhibited significantly higher levels of monounsaturated-and polyunsaturated fatty acids, respectively, compared to those of other groups. Umami-related free amino acids (Glu + Asp) were significantly higher in CE yolk than in KNC egg yolk. Multivariate analysis identified potential bio-volatile markers, including hexane, 3-ethyl-, hexadecane, and nonane, 2,5-dimethyl-, which could effectively differentiate between the yolk of various KNCs and CE. Notably, WRMD2E yolk exhibited substantial antioxidant power, as demonstrated by DPPH, ABTS, and ferric reducing antioxidant power assay. The overall results indicate that eggs from these native lines match the quality of a commercial egg product in many characteristics, with some superior traits, such as antioxidant capacity. The results of this study offer comprehensive insights into the egg yolk characteristics of KNC, particularly Woorimatdag chicken, providing fundamental data to enhance the utilization of KNC eggs in food applications while supporting efforts toward the conservation of native chicken biodiversity.

Objective: This study aimed to investigate effects of apparent metabolizable energy (AMEn) levels in diets on productivity, fat deposition, and biochemical parameters of Woorimatdag1 (WMD1) breeder pullets.Methods: A total of 240 four-week-old WMD1 breeder pullets were divided into four dietary groups with five replicates (12 birds per replicate). These groups had the following dietary energy levels: standard metabolizable energy (SME), SME-200, SME-100, and SME+100 (diets containing 2,800, 2,600, 2,700, and 2,900 kcal AMEn/kg, respectively). These pullets were provided with diets and water ad libitum until 16 weeks old.Results: Weight gain was significantly (p<0.05) higher in SME-100, SME, and SME+100 groups than in the SME-200 group. SME+100 and SME groups exhibited significantly (p<0.05) improved feed conversion ratio compared to the SME-200 group. Laying ages of 30% egg production occurred significantly (p<0.05) earlier in SME-100, SME, and SME+100 groups than in the SME-200 group. SME and SME+100 groups had significantly (p<0.05) higher liver fat (%) than the SME-200 group. Additionally, the SME+100 group had higher (p<0.05) abdominal fat (%) than other groups. However, blood parameters were not significantly different among dietary groups.Conclusion: SME-100 (2,700 kcal AMEn/kg) might be suitable for improving productivity and fat deposition of WMD1 breeder pullets.

Objective Yellow Korean native chicken (KNC-Y) is one of the five pure Korean indigenous chicken breeds that were restored through a government project in 1992. KNC-Y is recognized for its superior egg production performance compared to other KNC lines. In this study, we performed runs of homozygosity (ROH) analysis to discover selection signatures associated with egg production traits in the KNC-Y population. Methods A total of 675 DNA samples from KNC-Y were genotyped to generate single nucleotide polymorphism (SNP) data using custom 60K Affymetrix SNP chips. ROH analysis was performed using PLINK software, with predefined parameters set for the analysis. The threshold of ROH island was defined as the top 1% frequency of SNPs withing the ROH among the population. Results In the KNC-Y population, a total of 29,958 runs of homozygosity (ROH) fragments were identified. The average total length of ROH was 120.84 Mb, with each ROH fragment having an average length of 2.71 Mb. The calculated ROH-based inbreeding coefficient (FROH) was 0.13. Furthermore, we revealed the presence of ROH islands on chromosomes 1, 2, 4, 5, 7, 8, and 11. Within the identified regions, a total of 111 genes were annotated, and among them were genes related to economic traits, including PRMT3, ANO5, HDAC4, LSS, PLA2G4A, and PTGS2. Most of the overlapping quantitative trait locus regions with ROH islands were found to be associated with production traits. Conclusion This study conducted a comprehensive analysis of ROH in the KNC-Y population. Notably, among the findings, the PTGS2 gene is believed to play a crucial role in influencing the laying performance of KNC-Y.

This study assessed the trends in inbreeding, effective population size, and genetic diversity across six Korean native chicken lines using pedigree records from 54,383 chickens. Understanding these genetic parameters is significantly important for maintaining healthy and viable chicken populations. The primary objective was to analyze the pedigree data to assess the levels of inbreeding and genetic diversity and to evaluate the effective population size across the different lines. Pedigree analysis revealed that pedigree completeness peaked in the first generation and declined in subsequent generations for all lines. Line A exhibited a mean inbreeding coefficient of 0.0201, whereas the other lines displayed lower mean values ranging from 0.0009 to 0.0098, indicating that inbreeding levels were within an acceptable range and considered safe from extinction. Average relatedness consistently increased with time. Individual increases in inbreeding were the highest in Line A (0.62%), with smaller increases in the other lines ranging from 0.02 to 0.23%. Effective population sizes varied from 81 to 2500, with average coancestry within parental populations ranging from 0.0032 to 0.0290. The fe/fa ratio between 1.00 and 1.69 in the 6 lines suggested a moderate impact during bottleneck events, with subsequent populations recovering well. The genetic diversity loss due to genetic drift and unequal founder contributions ranged from 0.66-3.15%, indicating that considerable genetic variability remains within the populations. The results of this study have practical applications in the management and conservation of genetic resources in poultry breeding programs. By highlighting the importance of monitoring inbreeding and maintaining genetic diversity, the findings can help develop strategies to ensure the long-term sustainability of these chicken lines. This study provides valuable insights into the genetic management of Korean native chicken lines, emphasizing the need for strategic breeding practices to preserve genetic health and diversity.

Korean native chickens (KNC) have a rich history and are highly regarded by Korean consumers owing their distinct flavors and textures. However, their slow growth and limited egg production pose challenges compared with commercial chicken breeds. To address these limitations and enhance economically important traits, such as growth and egg production, understanding their genetic foundations is necessary. We studied five KNC lines (F, H, S, W, and Y) and assessed them for weight at 8, 10, and 12 weeks of age and the total number of eggs laid. The analysis incorporated pedigree data from 50773 chickens from Hanhyup Breeder chickens. Line F showed a mean inbreeding coefficient of 0.0017, whereas the other lines exhibited lower mean values ranging from 0.0005 to 0.0028, indicating that the inbreeding levels were within an acceptable range and considered safe from extinction. The average relatedness was 0.46%–1.88% among the studied lines. Heritability estimates for growth traits in line F were relatively high (ranging from 0.32 to 0.35), indicating a significant contribution of additive genetic variance and suggesting potential for genetic improvement through performance testing. However, the heritability of the egg production trait was low (0.07–0.16), indicating a greater role of non-genetic factors in explaining phenotypic variation. Management strategies should focus on improving these characteristics. Genetic correlations revealed strong positive associations between selected growth traits (up to 0.98), whereas all growth traits were negatively correlated with the total number of eggs laid. This suggests shared genetic influences on growth traits and highlights the potential for improving multiple correlated traits by enhancing the genetic performance of one trait. We also assessed the accuracy of estimated breeding values (EBVs), which ranged from 0.55 to 0.69 and 0.42 to 0.58 for growth traits and egg production trait, respectively. These moderately accurate estimates indicated that EBVs can effectively indicate the true breeding value of an animal. To improve accuracy, it is essential to maintain reliable phenotypic and pedigree records, as well as increase the number of animals in the flock. Therefore, this study provides insights into the genetic parameters and breeding value accuracy of growth and egg production traits in KNC, facilitating future genetic improvement programs for these economically important traits.

The effect of cinnamon powder on the quality and mitigation of off-flavor in fried chicken drumsticks made from long-term thawed Korean native chicken (Woorimatdag No. 1, WRMD1) was investigated. The WRMD1 drumsticks were categorized into 5 groups: conventional thawing (16 h, CT), long-term thawing (48 h, LT), cinnamon powder added into 'LT' as marinade (0.03%, CM) or incorporated into the batter (1.35%, CB), and long-term thawing with cinnamon powder incorporated both in the marinade and batter (0.03% + 1.35%, CMB). The crude fat content was significantly higher in the CT and CMB than that of the CB. The CM, CB, and CMB showed significantly lower levels of 2-thiobarbituric acid reactive substance compared with the CT and LT. The predominant fatty acids in all treatments were C18:1n9, C18:2n6, and C16:0. The LT displayed lower total unsaturated fatty acid content than the CT (P < 0.05). The CM effectively decreased lipid oxidative volatiles, such as 1-octanol, 1-octen-3-ol, and 2-octen-1-ol, (E), in the LT (P < 0.05). Both the CM and CB showed an inclination to increase specific pyrazines associated with pleasant notes compared with the LT, and showed higher levels of pyrazines, such as pyrazine, 2-ethyl-6-methyl-, and pyrazine, 3-ethyl-2,5-dimethyl-, than those of the CMB (P < 0.05). The CM contained higher levels of 2,3-butanedione when compared with the other groups (P < 0.05). Multivariate analysis demonstrated that cinnamon had an effect in discriminating the treatment groups with cinnamon addition from both the CT and LT, whereas the CM, CB, and CMB formed distinct clusters. The CM and CMB received significantly higher aroma scores from panelists in comparison to the other groups. These findings suggest that the CM (0.03% cinnamon powder) can be used to enhance the aroma in fried WRMD1 drumsticks by reducing or masking the off-flavor volatiles associated with long-term thawing.

This study was conducted to investigate the composition of the fatty acids in the breast meat of Red-brown Korean native chickens (KNC-R). This study used a total sample of three hundred eighty-two KNC-R (males: 190, females: 192). We used the fatty acid methyl ester (FAME) method to extract the fatty acids. A 2-way ANOVA of the R program was used to assess the effects of batch and sex on each fatty acid trait. Analysis of the fatty acid in the sampled population showed that the predominant fatty acid was oleic acid (C18:1; 28.252%) which is monounsaturated fatty acid (MUFA), followed by palmitic acid (C16:0; 20.895%), saturated fatty acid (SFA), and two omega-6 polyunsaturated fatty acid (PUFAs): linoleic (C18:2; 15.975%), and arachidonic (C20:4; 10.541%). Indices used to evaluate the nutritional quality of fat in the diet: ratio between PUFAs and SFAs (P/S), thrombogenicity index (TI), and atherogenicity index (AI) were calculated and were 0.959, 0.814, and 0.355, respectively. Currently, meat consumers need healthier fatty acids. Therefore, information on the content of fatty acid in chicken meat is very important for meat consumers in choosing the type of the meat to be consumed.

Objective: Carnosine and anserine affect the meat flavor. The contents of carnosine and anserine in meat are affected by genetic and environmental factors. This study aimed to discover the single-nucleotide polymorphisms (SNPs) in the histamine-N-methyl transferase ( HNMT ) and histamine-N-methyl transferase-like ( HNMT-like ) genes and to associate them with the content of carnosine and anserine in Korean native chicken- red brown line (KNC-R). Methods: This study used a total of 384 birds (males, n = 192; females, n = 192) aged 10 weeks old, for genotyping HNMT and HNMT-like genes. One synonymous SNP (rs29009298C/T) of the HNMT gene was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods whereas four missense SNPs (rs734406537G/A; rs736514667A/G; rs15881680G/A and rs316765035T/C) of the HNMT gene, and one missense SNP rs737657949A/C of the HNMT-like gene were genotyped by PCR allele competitive extension (PACE) genotyping technology. Two-way analysis of variance of the R program was used to associate HNMT genotypes with the contents of carnosine and anserine in KNC-R chickens. Results: There were significant associations (p<0.05) between the genotypes of the synonymous SNP:rs29009298C/T, missense SNP rs736514667A/G of the HNMT gene and the content of carnosine in KNC-Rs. This study also reported the sex effect on the carnosine content, where females had more content of carnosine compared to that of male KNC-R. Conclusion: Two SNPs (synonymous: rs735769522C/T) and missense: rs736514667A/G) in the HNMT gene might be used as genetic markers in the selection and breeding of chickens with better taste and high-flavored meat.

This study investigated the effect of dietary supplementation with phytase on growth performance, fecal excretion, and compost nutrition on broilers fed available phosphorus (avP)- and calcium (Ca)-deficient diets. A total of 750 one-day-old broiler chicks were randomly divided into five dietary groups having ten replications in a floor house. Diets of the groups were formulated with positive control (PC), negative control (NC; low avP and Ca), and NC supplemented with phytase levels; 500 (NC500), 1,000 (NC1000), and 1,500 FTU/kg (NC1500). A three-phase feeding program was used in the trial. Average daily gain (ADG) and average daily feed intake (ADFI) in the groups fed diets supplemented with phytase were significantly (p < 0.05) higher than those fed NC and the increase was equivalent to those fed PC. Serum levels of Ca and phosphorus (P) were higher (p < 0.05) in broilers fed NC1000 and NC1500 than in those fed NC. Interleukin (IL) level was the lowest in the group fed NC. Plasma myo-inositol (INS) concentrations in the NC1500 group were higher (p < 0.05) than PC, NC, and NC500 groups. Crude protein (CP) excretion was notably (p < 0.05) lower in the NC1500 group than in PC and NC groups. A lower (p < 0.05) concentration of P2O5 was observed in compost from the group fed NC1500 than the groups fed PC and NC. Accordingly, we suggest that phytase supplementation in lower avP and Ca levels of broiler diet can improve their productive performance and reduce environmental pollution.