Egg Production Traits Research Articles

Identification of quantitative trait locus and positional candidate loci influencing chicken egg quality under tropical conditions.

Egg quality is a vital factor in the poultry industry. High-quality eggs not only meet consumer expectations for appearance, taste, and nutritional value but also have high marketability, profitability, and consumer satisfaction. Accordingly, we executed our research with the purpose of determining chromosomal regions and genetic markers associated with egg quality in an F2 cross-bred chicken population under tropical conditions; we determined these through a genome-wide association study and quantitative trait locus (QTL) mapping. This population was created by cross-breeding the L2 line of Taiwan Country chickens, which is adapted to local conditions in Taiwan, with an experimental line (R-line) of Rhode Island Red layer chickens, which was developed by the French National Research Institute for Agriculture, Food and the Environment. A 60K single nucleotide polymorphism (SNP) genotyping array for chickens was employed to execute the analysis. Our analysis revealed 40 QTLs associated with egg quality under tropical conditions, namely 20 QTLs with genome-wide statistical significance and 20 QTLs with chromosome-wide statistical significance. Furthermore, we identified 93 SNPs exerting discernible effects on egg quality, with 10 of these effects exhibiting genome-wide significance and 83 exhibiting potential significance. The majority of the detected QTL regions and SNPs agreed with those identified as having an association with egg quality or production traits in previous studies, thus supporting the interrelationships determined between the studied characteristics. The findings of this study enhance the understanding regarding the genetic regulation governing chicken egg quality, thereby serving as a valuable reference for future functional investigations.

Transcriptome analyses of shell color and egg production traits between the uteruses of blue-green eggshell chickens and Hy-Line brown layers

Blue-green eggs exhibit unique shell color; however, compared to commercial layers, blue-green eggshell chickens have lower egg production and lack uniform shell colors. Aiming to confirm the molecular mechanisms that affect shell color and egg production, this study collected the uteruses of 12 blue-green eggshell chickens (BG group) and six Hy-Line layers (Brown group), which had significantly different shell color indexes (SCI) and egg numbers at 300 days of age (EN300). Transcriptome sequencing and comparative analyses were subsequently performed. BG hens were divided into two groups for comparative analysis (BGblue vs. BGgreen and BGlow vs. BGhigh, respectively), based on the differences in SCI and EN300, respectively. The result of weighted gene co-expression network (WGCNA) analysis showed that the sequenced and mapped 16,785 genes were clustered into 18 modules, among which six modules with a total of 4270 genes were highly correlated with SCI and EN300 traits. Five hundred and eleven differentially expressed genes (DEGs) belonged to the six key modules. Through KEGG mapping, GO enrichment, and Cytoscape network analysis, nine Hub genes were tightly associated with SCI and EN300. The up-regulated genes were CCR2, CCR8, CD40LG, IL18RAP, INHBA, and P2RY13, while the down-regulated genes were ABCA13, ADCY2, and GRM1. Co-analyses with the results of comparisons between the BG subgroups revealed that the expression of solute carrier (SLC) proteins and ABC transporters were highly related to eggshell color, while cytokine-cytokine receptor interactions and neuroactive ligand-receptor interactions were key pathways affecting egg production. The expression of extracellular cytokines and membrane receptors were significantly up-regulated in low-yield chickens. The candidate DEGs and pathways found in the study will assist in clarifying the molecular mechanisms affecting shell color and egg production, and improve the breeding of blue-green eggshell chickens.

Comparison of productive performance of Marandi, White Leghorn, and Marandi-White Leghorn crossbred chickens

BackgroundRecently, efforts like crossbreeding, strain crossing, and inbred hybridization have been performed to improve productive performance in native chickens. This experiment was carried out to evaluate the effects of crossbreeding on the improvement of the productivity of a native chicken. The White Leghorn exotic chicken (WL) as dam line and the Marandi indigenous chicken (MA) as sire line were used to generate the crossbreds (MA × WL). Body weight and egg production traits were measured in the three groups.ResultsThere are significant performance differences between WL and MA, with WL exhibiting superior body weight and egg production compared to MA (P < 0.05). Crossbreeding between WL and MA significantly improved most traits, with MA × WL outperforming MA. Negative heterosis was observed for body weight showing similarities between MA and MA × WL. Notably, MA × WL showed a closer resemblance to WL than MA in hen-day egg production at 40 and 44 weeks (P < 0.05).ConclusionsThe results derived from this study show that the economic performance of native chickens can be enhanced through crossbreeding with exotic chickens. Using the crossbred chickens in rural areas can be more efficient than the native chickens. In addition, the resilience of the native chickens to the local environment can be transmitted genetically to the crossbred which should be investigated in further studies.

Effects of substitution of crude palm oil with palm-pressed fibre oil on the laying hen's performance, egg production and egg quality traits.

This study aimed to evaluate the effects of substituting a crude palm oil (CPO) diet with palm-pressed fibre oil (PPFO) on laying hens' performance, egg production, carcass characteristic and egg quality. A total of 150 Hisex Brown laying hens were randomly assigned to five treatments: a basal diet containing 4% CPO (T1-control) and basal diets in which CPO was substituted by 25% (T2), 50% (T3), 75% (T4) or 100% (T5) PPFO. These diets were fed to laying hens ad libitum for 16 weeks. Compared to the T1 diet, dietary treatments T2, T3 and T4 had no significant effect (P > 0.05) on the feed intake, body weight gain, feed conversion ratio, egg number, egg production, egg weight and egg mass of the laying hens during the entire experimental period. Nonetheless, a significant (P < 0.05) reduction in feed intake, egg number, egg production and egg mass were observed in hens fed T5 compared to those fed the T1 (control) diet. Except for heart and spleen weights, other carcass characteristics were not affected by treatment (P < 0.05). Skin yellowness and breast meat redness increased significantly (linearly, P < 0.05) with increasing proportions of PPFO. Likewise, yolk colour scores increased in proportion to the dietary level of PPFO (linearly, P < 0.05). These findings suggest that PPFO can be used as a novel, cost-effective lipid source at a level of 3% in layer diets as a substitute for CPO to improve eggs' quality parameters without any harmful effects on laying performance.

Expression profiling and single nucleotide polymorphism of mitogen-activated protein kinase kinase kinase 8 MAP3K8 in white muscovy ducks (Cairina moschata)

A previous study on ovarian and hypothalami transcriptome analysis in white Muscovy duck revealed that MAP3K8 gene participated in MAPK signaling pathway that influence egg production. Additionally, MAP3K8 was predicted as a target gene of miRNA-509-3p that promotes the secretion of oestradiol which is an important hormone in egg ovulation. This suggested that MAP3K8 might have a functional role in the reproductive performance “egg production” of white Muscovy ducks. Herein, we focused on expression level of MAP3K8 in reproductive and non-reproductive tissues of highest (HP) and lowest (LP) egg producing white Muscovy ducks and identified the polymorphism in MAP3K8 and its association with three egg production traits; Age at first egg (AFE), number of eggs at 300 days (N300D) and 59 weeks (N59W). The results of expression level indicated that mRNA of MAP3K8 was significantly (p < 0.01) expressed in the oviduct than in the ovary and hypothalamus. Seven synonymous SNPs were detected, and association analysis showed that g.148303340 G>A and g.148290065 A>G were significantly (p < 0.05) associated with N300D and N59W. The results of this study might serve as molecular marker for marker-assisted selection of white Muscovy ducks for egg production.

Integrating Genomics and Transcriptomics to Identify Candidate Genes for Egg Production in Taihe Black-Bone Silky Fowls (Gallus gallus domesticus Brisson).

The Taihe Black-Bone Silky Fowl (Gallus gallus domesticus Brisson) possesses significant value in terms of consumption, medicinal applications, and ornamental appeal, representing a precious genetic resource and traditional Chinese medicinal material. However, considerable variation exists within populations regarding egg-laying performance. This study integrates a whole-genome selection signal analysis (SSA) with a transcriptome analysis to identify genes associated with egg-laying traits in Taihe Black-Bone Silky Fowls. We identified 31 candidate genes under selection from the high-yield chicken (HC) and low-yield chicken (LC) groups. Additionally, through RNA-seq analysis, 257 common differentially expressed genes (DEGs) were identified from four comparative groups. Two overlapping genes-LPL and SETBP1-were found in both the selected gene and DEG lists. These selected genes and DEGs were enriched in pathways related to ovarian development, including the lysosome pathway, the ECM-receptor interaction pathway, the TGF-beta signaling pathway, the Wnt signaling pathway, the PPAR signaling pathway, and the glycerolipid metabolism pathway. These research findings contribute to the breeding of Taihe Black-Bone Silky Fowls with high egg production traits and provide a theoretical foundation for exploring the regulatory mechanisms of avian reproduction.

The Effects of Rearing Systems on Incubation, Egg Production and Quality Traits in Pharaoh Quails

This study was conducted to determine the effect of rearing quails in different rearing systems on egg production, egg quality characteristics, and incubation results. The 360 quails were distributed equally to 3 different rearing groups (cage, enriched cage, and floor) in a male:female mixed at the age of 3 weeks. The eggs were individually weighed and recorded one by one daily (5487 eggs) for 3 months. To determine egg quality and incubation characteristics, 750 eggs were broken, and 3284 eggs were incubated, respectively. The results showed that female quail in the floor group have lower body weight at 6 weeks old (177.19 g), and they reached sexual maturity (age of first egg laying) later (65.36 day, P&lt;0.01), The lowest egg production (61.14%) occurred in the floor group during the 3-month egg production period (P&lt;0.05). The lowest average egg weight (9.07 g) was determined in the floor group (P&lt;0.05). It was determined that the eggs of quails raised in the enriched group had a rounder shape index because they have larger widths (P&lt;0.01). While the highest average yolk height (11.24 mm) was determined in the enriched cage group (P&lt;0.01), the highest averages of albumen length (72.41 mm) and lowest averages of yolk index (48.43%) were determined in the cage group (P&lt;0.01). The lowest average values (113.17) in Haugh unit were detected in the floor group (P&lt;0.05). The highest fertility rate (98.44%) was in Floor♂:Cage♀, the highest hatchability of fertile egg rate (94.67%) was obtained from Enriched♂:Cage♀, and the highest hatchability (89.10%) was obtained from Floor♂:Cage♀ pairing (P&lt;0.05). The lowest fertility rate (88.00%) was obtained from the Enriched♂:Floor♀, the lowest hatchability of fertile egg rate (86.01%) was obtained from the Enriched♂:Enriched♀, and the lowest hatchability (75.62%) was obtained from the Enriched♂: Enriched♀ groups. As a result, it has been revealed that the effect of various rearing systems is different on egg production, egg quality traits, and hatching results in quails. Thus, it has been shown that different programs at the rearing period to be applied to the male and female quails can achieve better incubation results and reproductive success.

Hemoglobin polymorphism and its association with morphometric and egg production traits in Ethiopian indigenous and Sasso chicken breeds.

The present study investigated the biochemical polymorphism of hemoglobin (Hb) and its relationship with performance traits of Ethiopian indigenous and Sasso chicken breeds. A total of 284 chickens reared in three agro-ecologies were examined for genetic diversity and associations with productive traits at Hb locus using agarose gel electrophoresis. The results showed that the HbA allele was dominant in both breeds, and a higher proportion of male chickens were HbAA genotypes, while females were predominantly HbBB types. In the highland agro-ecology, chickens with the HbAA genotype were the most dominant, whereas in mid- and low-land agro-ecologies, chickens with HbBB and HbAB genotypes were found to be more frequent. A moderate level of expected heterozygosity was obtained with 0.47 and 0.445 for indigenous and Sasso chickens, respectively, with an average effective number of alleles per locus of 1.89 and 1.80. Moreover, chickens with HbAA genotypes showed significantly (p ≤ 0.05) higher body weight and linear body measurements than those of HbAB and HbBB genotypes. However, for appendage body structures (comb and wattle dimensions), chickens with the HbAB and HbBB genotypes had higher mean values. Additionally, clutch size (14.2 ± 0.4), clutch length (21.8 ± 0.7), and eight-month egg production (84.1 ± 1.2) were significantly (p ≤ 0.05) higher for hens with HbBB genotypes, followed by those with HbAB-types. Therefore, the considerable hemoglobin variability and significant associations of Hb variants with the performance traits can be sought as guiding information for further genetic improvement interventions in the chicken breeds under investigation. Further microsatellite marker-based genotyping is recommended to validate the higher morphometric values for HbAA genotypes and the better egg production for HbBB and HbAB genotypes.

Comparison of genomic prediction accuracy using different models for egg production traits in Taiwan country chicken

In local chickens targeted for niche markets, genotyping costs are relatively high due to the small population size and diverse breeding goals. The single-step genomic best linear unbiased prediction (ssGBLUP) model, which combines pedigree and genomic information, has been introduced to increase the accuracy of genomic estimated breeding value (GEBV). Therefore, this model may be more beneficial than the genomic BLUP (GBLUP) model for genomic selection in local chickens. Additionally, the single-step genome-wide association study (ssGWAS) can be used to extend the ssGBLUP model results to animals with available phenotypic information but without genotypic data. In this study, we compared the accuracy of (G)EBVs using the pedigree-based BLUP (PBLUP), GBLUP, and ssGBLUP models. Moreover, we conducted single-SNP GWAS (SNP-GWAS), GBLUP-GWAS, and ssGWAS methods to identify genes associated with egg production traits in the NCHU-G101 chicken to understand the feasibility of using genomic selection in a small population. The average prediction accuracy of (G)EBV for egg production traits using the PBLUP, GBLUP, and ssGBLUP models is 0.536, 0.531, and 0.555, respectively. In total, 22 suggestive- and 5% Bonferroni genome-wide significant-level SNPs for total egg number (EN), average laying rate (LR), average clutch length, and total clutch number are detected using 3 GWAS methods. These SNPs are mapped onto Gallus gallus chromosomes (GGA) 4, 6, 10, 18, and 25 in NCHU-G101 chicken. Furthermore, through SNP-GWAS and ssGWAS methods, we identify 2 genes on GGA4 associated with EN and LR: ENSGALG00000023172 and PPARGC1A. In conclusion, the ssGBLUP model demonstrates superior prediction accuracy, performing on average 3.41% than the PBLUP model. The implications of our gene results may guide future selection strategies for Taiwan Country chickens. Our results highlight the applicability of the ssGBLUP model for egg production traits selection in a small population, specifically NCHU-G101 chicken in Taiwan.

Effects of low dietary calcium and lipopolysaccharide challenges on production performance, eggshell quality, and bone metabolism of laying hens.

Dietary calcium supply is essential for bone development and egg production in laying hens. This study investigated the effects of low dietary calcium and lipopolysaccharide (LPS) induced immune challenge in aged laying hens. A total of thirty-two Hy-Line Brown laying hens at 80 weeks old with an average laying rate of 62% were randomly divided into two groups and fed a normal calcium diet (3.57% Ca, NCA) or low calcium diet (2.08% Ca, LCA). At 88 weeks, the experiment was designed using a 2 × 2 factorial arrangement, and hens were intraperitoneally injected with saline (SAL) or LPS (0.5mg/kg, 0.5mg/kg, or 1.5mg/kg body weight) once every 48h intervals over 5 days. Production performance, egg quality, and bone physiology were evaluated. Results showed that LPS challenge decreased the hen-day egg production, egg mass, and eggshell traits (p < 0.05), but increased (p < 0.05) the calcium content of the tibia compared to SAL-injected hens. LCA diet decreased (p < 0.05) the hen-day egg production, and eggshell traits such as weight, percentage, strength, and thickness compared to the NCA diet. LCA diet increased the serum alkaline phosphatase (ALP) activity (p < 0.01) and tibial expression of ALP (p < 0.05) compared to NCA diet. LPS injection suppressed both the serum ALP activity (p < 0.05) and tibial expression of ALP (p < 0.001) compared to SAL injection. Furthermore, LPS injection increased (p < 0.05) the expression of both pro and anti-inflammatory cytokines in the spleen and tibia. The expression of cathepsin K ( Cts K ) and matrix metalloproteinase 9 ( MMP-9 ) were downregulated by LPS injection (p < 0.001). Broken and shell-less egg production and calcium content of eggshell, as well as tibial mRNA expression of osteocalcin ( Ocn ), tumor necrosis factor-alpha ( TNF-α ) and tartrate-resistant acid phosphatase ( TRAP ) were affected by the interaction (p < 0.05) of diet and injection. Therefore, this study demonstrated that to certain extents, low dietary calcium and LPS challenge dysregulated bone homeostasis and metabolism, with detrimental effects on the performance and eggshell quality of aged laying hens.

Relative Phenotypic Performance of Crossbred Chicken as Step in Synthetic Breed Development in Ethiopia: A Review

The present review article aims to provide and summarize synthesized information regarding some of economically important traits on reproductive and productive performance of crossbred chicken to develop both adaptive and sustainable breed to the intended beneficiaries. Growth traits, egg production traits, reproductive traits and other economically important traits of crossbred chicken were assessed in comparison to their counterparts purebred breed both native and exotic parents. In the majority of crossbreeding studies, the hybrids surpassed the original native parental breeds in various traits studied, including body weight, feed conversion ratio, age at first egg, egg production, egg weight, and egg mass. The majority of hybrids achieved sexual maturity at an earlier age, laid more eggs, and produced a greater egg mass when compared to local chickens. Eggs from the hybrids were also heavier than those from the local chickens in certain crossbreeding experiments. In overall, crossbred chickens that combine the blood of exotic and local breeds tend to perform relatively better than indigenous chickens, which are typically characterized in low production due genetics. The frequent production of F1 crossbred demands in subsequent importation of exotic parent due to produced offspring chicken are terminal genetically. Also, the degree of heterosis retained in the crossbred decreased as generation increased due recombinant ad segregations effects. To overcome such problem producing adaptive and sustainable chicken breed through synthetic breeding is crucial for developing countries like Ethiopia.

Genome-wide association study identified candidate genes for egg production traits in the Longyan Shan-ma duck

Egg production is an important economic trait in layer ducks and understanding the genetics basis is important for their breeding. In this study, a genome-wide association study (GWAS) for egg production traits in 303 female Longyan Shan-ma ducks was performed based on a genotyping-by-sequencing strategy. Sixty-two single nucleotide polymorphisms (SNPs) associated with egg weight traits were identified (P < 9.48 × 10-5), including 8 SNPs at 5% linkage disequilibrium (LD)-based Bonferroni-corrected genome-wide significance level (P < 4.74 × 10-6). One hundred and nineteen SNPs were associated with egg number traits (P < 9.48 × 10-5), including 13 SNPs with 5% LD-based Bonferroni-corrected genome-wide significance (P < 4.74 × 10-6). These SNPs annotated 146 target genes which contained known candidate genes for egg production traits, such as prolactin and prolactin releasing hormone receptor. This study identified that these associated genes were significantly enriched in egg production-related pathways (P < 0.05), such as the oxytocin signaling, MAPK signaling, and calcium signaling pathways. It was notable that 18 genes were differentially expressed in ovarian tissues between higher and lower egg production in Shan-ma ducks. The identified potential candidate genes and pathways provide insight into the genetic basis underlying the egg production trait of layer ducks.

Genome-Wide Association Analysis and Genetic Parameters for Egg Production Traits in Peking Ducks.

Egg production traits are crucial in the poultry industry, including age at first egg (AFE), egg number (EN) at different stages, and laying rate (LR). Ducks exhibit higher egg production capacity than other poultry species, but the genetic mechanisms are still poorly understood. In this study, we collected egg-laying data of 618 Peking ducks from 22 to 66 weeks of age and genotyped them by whole-genome resequencing. Genetic parameters were calculated based on SNPs, and a genome-wide association study (GWAS) was performed for these traits. The SNP-based heritability of egg production traits ranged from 0.09 to 0.54. The GWAS identified nine significant SNP loci associated with AFE and egg number from 22 to 66 weeks. These loci showed that the corresponding alleles were positively correlated with a decrease in the traits. Moreover, three potential candidate genes (ENSAPLG00020011445, ENSAPLG00020012564, TMEM260) were identified. Functional enrichment analyses suggest that specific immune responses may have a critical impact on egg production capacity by influencing ovarian function and oocyte maturation processes. In conclusion, this study deepens the understanding of egg-laying genetics in Peking duck and provides a sound theoretical basis for future genetic improvement and genomic selection strategies in poultry.

Characterization of chicken Relaxin3 gene: mRNA expression and response to reproductive hormone treatment in ovarian granulosa cells, and single nucleotide polymorphisms associated with egg laying traits in hens

As a protein structurally similar to insulin, relaxin3 (RLN3) plays a role in promoting arousal, suppressing depressive or anxious behaviors. Two studies revealed the increase of RLN3 expression during chicken follicle selection. In this study, by real-time quantitative PCR and luciferase assay, mRNA expression and single nucleotide polymorphisms (SNPs) of chicken RLN3 were investigated. The mRNA expression of chicken RLN3 was higher in the granulosa cell of hierarchal follicles (Post-GCs) than that of pre-hierarchal follicles (Pre-GCs). In Pre-GCs, the mRNA expression of chicken RLN3 was stimulated by FSH and progesterone; in Post-GCs, it was stimulated by higher concentration of estrogen and FSH, however, was inhibited by progesterone. Four SNPs including g.-655G > C, g-592G > A, g.-372T > A and g.-282G > C were identified in the critical promoter region from −1291 bp to −207 bp of chicken RLN3, among which g.-655G > C, and g-592G > A were associated with age at first laying and clutch size, respectively, in Zaozhuang Sunzhi chickens. At g.-655G > C and g-592G > A, allele C and allele A had higher transcriptional activity, respectively. These data suggest that RLN3 plays an important role in chicken follicle development and SNPs in its promoter region are potential DNA markers for improving egg production traits.

Phenotypic Identification, Genetic Characterization, and Selective Signal Detection of Huitang Duck.

The Huitang duck (HT), a long-domesticated elite local breed from Hunan Province, China, with excellent meat quality, has not had its population genetic structure and genomic selective sweeps extensively studied to date. This study measured the phenotypic characteristics of HT and conducted comparative analysis between HT and 16 different duck breeds, including wild, indigenous, and meat breeds, to characterize its population structure and genetic potential. The results revealed that HT is a dual-purpose indigenous breed with a genetic background closely related to the Youxian sheldrake and Linwu ducks. In the selective sweep analysis between HT and Linwu ducks, genes such as PLCG2, FN1, and IGF2BP2, which are associated with muscle growth and development, were identified near the 27 selection signals. The comparison between HT and Jinding ducks revealed 68 selective signals that contained important genes associated with ovarian development (GRIK4, MAP3K8, and TGIF1) and egg-laying behaviors (ERBB4). Selective sweep analysis between HT and Youxian sheldrake ducks found 93 selective regions covering genes related to both meat (IGF1R and IGFBP5) and egg-production (FOXO3 and ITPR1) traits. Our study may provide novel knowledge for exploring the population structure and genetic potential of HT, offering a theoretical basis for its breeding strategies in the future.

Relative Phenotypic Performance of Crossbred Chicken as Step in Synthetic Breed Development in Ethiopia: A Review Article

The present review article aims to provide and summarize synthesized information regarding some of economically important traits on reproductive and productive performance of crossbred chicken to develop both adaptive and sustainable breed to the intended beneficiaries. Most of crossing were used full diallel mating design in both direct and reciprocal ways. Growth traits, egg production traits, reproductive traits and other economically important traits of crossbred chicken were assessed in comparison to their counterpart’s purebred both native and exotic parents. In the majority of crossbreeding studies, the hybrids surpassed the original native parental breeds in various traits studied, including body weight, feed conversion ratio, age at first egg, egg production, egg weight, and egg mass. The majority of hybrids achieved sexual maturity at an earlier age, laid more eggs, and produced a greater egg mass when compared to local chickens. Eggs from the hybrids were also heavier than those from the local chickens in certain crossbreeding experiments. In overall, crossbred chickens that combine the blood of exotic and local breeds tend to perform relatively better than indigenous chickens, which are typically characterized in low production due genetics. The frequent production of F&amp;lt;sub&amp;gt;1 &amp;lt;/sub&amp;gt;crossbred demands in subsequent importation of exotic parent due to produced offspring chicken are terminal genetically. Also, the degree of heterosis retained in the crossbred decreased as generation increased due recombinant ad segregations effects. To overcome such problem producing adaptive and sustainable chicken breed through synthetic breeding is crucial for developing countries like Ethiopia.

CYP24A1 and TRPC3 Gene Expression in Kidneys and Their Involvement in Calcium and Phosphate Metabolism in Laying Hens.

Ca and P homeostasis across the egg-laying cycle is a complex process involving absorption in the small intestine, reabsorption/excretion in the kidneys, and eggshell gland secretion. Diets with inadequate calcium and phosphorus can interfere with their absorption and digestibility, resulting in eggshell quality losses and reduced productive life, affecting egg production and welfare. A better understanding of gene expression profiles in the kidneys of laying hens during the late egg-laying period could clarify the renal role in mineral metabolism at this late stage. Therefore, the performance, egg quality and bone integrity-related traits, and expression profiles of kidney candidate genes were evaluated in 73-week-old laying hens receiving different Ca and P ratios in their diet: a high Ca/P ratio (HR, 22.43), a low ratio (LR, 6.71), and a medium ratio (MR, 11.43). The laying hens receiving the HR diet had improved egg production and eggshell quality traits compared to the other two groups. Humerus length was shorter in the HR than in the other groups. The CYP24A1 and TRPC3 genes were differentially expressed (p.adj ≤ 0.05) among the groups. Therefore, their expression profiles could be involved in calcium and phosphate transcellular transport in 73-week-old laying hens as a way to keep mineral absorption at adequate levels.

Runs of homozygosity analysis for selection signatures in the Yellow Korean native chicken.

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. 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. 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. 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.

Effect of using hydroxychloride as a copper source on performance, eggshell quality, tibia properties, mineral excretion, and antioxidant capacity of yolk in layer quails

Abstract This research aimed to examine the impact of varying levels of dietary copper (Cu) hydroxychloride on the performance, egg quality, yolk antioxidant capacity, tibia traits, and mineral excretion in laying quails. 125 female 10-week-old quails were randomly distributed into five experimental groups with five replicates, each consisting of five quails. Five experimental isonitrogenous and isoenergetic diets were designed to contain different Cu hydroxychloride (54% Cu) levels at 7.20 (basal diet), 15, 30, 45 and 60 mg/kg respectively. Quails were fed with trial diets for 12 weeks. Performance, egg production, eggshell quality, and biomechanical traits of the tibia were not impacted (P &gt; 0.005) by variations in dietary Cu levels. Yolk antioxidant capacity, measured as yolk DPPH value, exhibited an increase (P &lt; 0.01) in the high-dose group (60 mg/kg). Regarding tibia mineral concentration, Cu concentration decreased linearly (P &lt; 0.001) with increasing Cu level, manganese and zinc content recorded the highest values in quails that had received 60 mg/kg Cu in the diet (P &lt; 0.01), while the lowest phosphorus content was described for 45 and 60 mg/kg. Contrarily, increases (P &lt; 0.01) in dietary Cu resulted in raised faecal Cu content, while phosphorus, manganese, and zinc, were reduced when Cu was added. It can be inferred that adding Cu to the diet of laying quails would not be necessary, which in turn decreases Cu excretion and prevents substantial environmental harm.

Artificial selection footprints in indigenous and commercial chicken genomes

BackgroundAlthough many studies have been done to reveal artificial selection signatures in commercial and indigenous chickens, a limited number of genes have been linked to specific traits. To identify more trait-related artificial selection signatures and genes, we re-sequenced a total of 85 individuals of five indigenous chicken breeds with distinct traits from Yunnan Province, China.ResultsWe found 30 million non-redundant single nucleotide variants and small indels (< 50 bp) in the indigenous chickens, of which 10 million were not seen in 60 broilers, 56 layers and 35 red jungle fowls (RJFs) that we compared with. The variants in each breed are enriched in non-coding regions, while those in coding regions are largely tolerant, suggesting that most variants might affect cis-regulatory sequences. Based on 27 million bi-allelic single nucleotide polymorphisms identified in the chickens, we found numerous selective sweeps and affected genes in each indigenous chicken breed and substantially larger numbers of selective sweeps and affected genes in the broilers and layers than previously reported using a rigorous statistical model. Consistent with the locations of the variants, the vast majority (~ 98.3%) of the identified selective sweeps overlap known quantitative trait loci (QTLs). Meanwhile, 74.2% known QTLs overlap our identified selective sweeps. We confirmed most of previously identified trait-related genes and identified many novel ones, some of which might be related to body size and high egg production traits. Using RT-qPCR, we validated differential expression of eight genes (GHR, GHRHR, IGF2BP1, OVALX, ELF2, MGARP, NOCT, SLC25A15) that might be related to body size and high egg production traits in relevant tissues of relevant breeds.ConclusionWe identify 30 million single nucleotide variants and small indels in the five indigenous chicken breeds, 10 million of which are novel. We predict substantially more selective sweeps and affected genes than previously reported in both indigenous and commercial breeds. These variants and affected genes are good candidates for further experimental investigations of genotype-phenotype relationships and practical applications in chicken breeding programs.