Search Results (74)

The Tibetan chicken (TC) is a small indigenous breed native to the Qinghai–Tibet Plateau in China, exhibiting remarkable adaptation to the plateau’s extreme high-altitude environment. Its strong hypoxia tolerance is reflected in the ability to maintain normal embryonic cardiac structure and function during hypoxic incubation or high-altitude incubation. This study performed transcriptome sequencing of embryonic heart tissues from TC and White Leghorn (WL) incubated for 9, 11, and 16 days in Lhasa (altitude of 3650 m). A total of 1788 differentially expressed genes (DEGs) were identified through inter-breed comparison. Some DEGs were enriched in signaling pathways related to angiogenesis, apelin signaling, and myocardial contraction. Through integrating temporal expression analysis and weighted gene co-expression network analysis (WGCNA), we identified six key candidate DEGs (CREB3L2, MYH7B, CREB1, LOXL2, MICAL2, and AKAP13) that are involved in hypoxic response, myocardial structural remodeling, and regulation of signaling pathways. These genes likely represent core components of the molecular network underlying hypoxic adaptation in TC embryos. Overall, our findings provide a molecular basis for understanding the genetic mechanisms of hypoxic adaptation during embryonic cardiac development in chickens. Full article

The conventional method for detecting protein content in egg albumen is the Kjeldahl method, but this method cannot be applied in practical production due to cost limitations. Therefore, we developed albumen density (AD), which had certain potential application value in low-cost and efficient evaluation of albumen protein content. We calculated the heritability of AD in White Leghorn (WL) chickens and its correlation with average albumen protein quantity (AAP), total albumen protein quantity (TAP), albumen weight (AW), albumen volume (AV), egg weight (EW), albumen height (AH), haugh unit (HU), and yolk color (YC). It is worth noting that albumen protein content was measured in a small subset of samples. The average value of AD in eggs was 0.97 and its heritability was less than 0.1. The average value of AAP in eggs was 10.1%, and the average value of TAP in eggs was 2.95 g. There were significant positive correlations between AAP, TAP, AW, AV, AD, and EW, and there were strong positive genetic and phenotypic correlations between EW, AW, AV, and AD. The results of this study indicated that AD might have potential value as a supplementary tool for albumen protein trait selection in breeding. Full article

Laying hens require lighting for proper development and reproduction. There is limited research on the effects that lighting types have on birds’ welfare quality. A novel lighting source, Pulsed Alternating Wavelength System (PAWS), is being evaluated in the industry that claims to improve birds’ growth rate, decrease age at first egg, and decrease aggressive and nervous behaviors. Understanding how PAWS effects hen’s welfare, both physically and physiologically, is critical if this technology is to be adopted by industry. The project evaluated the effects of two PAWS lighting recipes on neurotransmitter turnover and welfare quality of commercial, conventionally caged laying hens. Three flocks of White leghorn hens (control [fluorescent lights] and two PAWS flocks [PAWS1 and PAWS2]) were sampled from 22 to 70 weeks of age, depending on the flock. The physical welfare of 50 hens per flock and neurotransmitter turnover of 10 hens per flock were assessed at each timepoint. The majority of welfare quality parameters were influenced by age as opposed to lighting type. No differences in dopamine turnover were observed. The hens housed under PAWS1 had reduced serotonin turnover, thus increased serotonin activity, and PAWS2 hens had improved keel bone damage scores; both indicative of improved welfare compared to control hens. The novel lighting may be beneficial to layer welfare, which may lead to increased longevity and productivity. Implementation in cage-free housing should be explored to delve into potential behavioral differences that could further influence welfare outcomes. Full article

Background/Objectives: The poultry industry faces severe heat-stress challenges that threaten both economic sustainability and animal welfare. Embryonic thermal manipulation (ETM) has been proposed as a thermal programming strategy to enhance chick heat tolerance, yet its efficacy in layers requires verification, and its effects on growth performance and neurodevelopment remain unclear. Methods: White Leghorn embryos at embryonic days 13 to 18 (ED 13–18) were exposed to 39.5 °C (ETM). Hatch traits and thermotolerance were recorded, and morphometric and histopathological analyses were performed on brain sections. Transcriptome profiling of the whole brains and hypothalami was conducted to identify differentially expressed genes (DEGs). Representative pathway genes responsive to ETM were validated by RT-qPCR. Results: ETM reduced hatchability, increased deformity rate, and decreased hatch weight and daily weight gain. During a 37.5 °C challenge, ETM chicks exhibited delayed panting and lower cloacal temperature. Histopathology revealed impaired neuronal development and myelination. Transcriptomic analysis of ED18 whole brains showed DEGs enriched in neurodevelopment, stimulus response, and homeostasis pathways. RT-qPCR confirmed hypothalamic sensitivity to ETM: up-regulation of heat-shock gene HSP70, antioxidant gene GPX1, the inflammatory marker IL-6, and apoptotic genes CASP3, CASP6, CASP9; elevated neurodevelopmental marker DCX, indicative of a stress-responsive neuronal state; and reduced orexigenic neuropeptide AGRP. Conclusions: ETM improves heat tolerance in layers but compromises hatching performance and brain development, with widespread perturbation of hypothalamic stress responses and neurodevelopmental gene networks. These findings elucidate the mechanisms underlying ETM and provide a reference for enhancing thermotolerance in poultry. Full article

The omega-3 polyunsaturated fatty acids (n-3 PUFA) in animal-derived foods are increasingly important for human health. Sacha inchi (Plukenetia volubilis L.), rich in n-3 PUFA, is a promising feedstuff for producing n-3 PUFA-enriched animal products. However, research on dietary Sacha inchi oil (SIO) supplementation in laying hens remains limited. Therefore, this study aimed to evaluate the effects of SIO on production performance, egg quality, and yolk fatty acid (FA) composition in laying hens. A total of 192 hybrid hens [(♂ White Leghorn × ♀ Egyptian Fayoumi); initial body weight: 1910 ± 22.14 g; age: 25 weeks old] were randomly assigned one of the four diets: a basal diet (CONT), and three tested diets based on CONT with the addition of 1.5%, 3.0%, and 4.5% SIO (as-feed basis) (SI15, SI30, and SI45, respectively). Each dietary treatment included 48 hens housed in 12 battery cages for 56 days with 4 birds per cage. Increasing dietary SIO levels significantly reduced average daily feed intake (p < 0.05). Egg yolk weight linearly increased (p < 0.05) with higher SIO inclusion, while other egg quality traits were unaffected. SIO supplementation significantly increased (p = 0.001) yolk n-3 PUFA level (from 0.79% to 8.29% on day 28, and from 0.87% to 9.13% on day 56) and substantially reduced the n-6/n-3 PUFA ratio by about nine-fold on both 28 and 56 days. In conclusion, SIO is a promising n-3 PUFA-rich feed ingredient for egg production. Adding 3.0–4.5% SIO in laying hen diets can enhance egg yolk weight and n-3 PUFA level while reducing feed intake without negatively affecting egg production or quality. Full article

In the chicken industry, sex determination significantly affects production efficiency and raises ethical concerns in poultry farming. As a key economic species, maximizing the advantages of each sex is vital in modern intensive breeding. Therefore, understanding the mechanisms of sex determination and regulation is critical to advancing the poultry industry. Transcriptome analysis of 3.5-day-old White Leghorn chicken embryonic genital ridges (n = 30, 15 males and 15 females) was performed using sex-pooled samples (five embryos/replicate, three replicates/sex). Sequencing generated 39.6 GB of high-quality reads for inter-sex comparative analysis, revealing 283 significantly differentially expressed genes (DEGs). The DEGs were primarily enriched in pathways such as ribosome biogenesis, glycan biosynthesis and metabolism, and TGF-β signaling, which are potential candidate pathways for the differentiation of chicken embryonic gonads. Key DEGs (including SMAD2Z, FREM1, NR2F1, SEMA6A, NFIB, RNF165, SMAD7B, SMAD2W, SPIN1W, and HINTW) were validated by RT-qPCR, confirming the transcriptome sequencing results. Among the DEGs, we predict binding sites for NR2F1 and NFIB within the DMRT1 gene promoter and suggest that these factors may serve as potential upstream activators for the expression of DMRT1, and they may initiate high DMRT1 expression in the subsequent stages of male embryos and regulate testicular development. In conclusion, this study investigated DEGs in the gonads of male and female chicken embryos after 3.5 days of incubation and found that NR2F1 and NFIB may serve as potential upstream activators for the expression of DMRT1, which is involved in the early determination of chicken sex. Full article

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

This study is based on the whole gene resequencing data of 162 individuals from 16 chicken breeds. We calculated the historical effective population size (Ne), differentiation time and genetic hybridization degree of the population to understand its historical dynamics, in order to provide a theoretical basis for the scientific protection and utilization of the germplasm resources of Baicheng Oil Chicken (BCY). The main results are as follows: using SMC++ and fastsimcoal2 software, respectively, we estimated Ne of BCY at 46,066 in the past and inferred a divergence time of 428–548 years ago. D-statistical analysis revealed a ~7% genetic introgression from White Leghorn chicken (LH) to BCY. Notably, infiltration genes such as CTNNAL1 (potentially influencing egg production) and RARX (possibly associated with fat deposition) were identified. These findings provide insights into BCY’s demographic history and support its genetic conservation and utilization. Full article

Evaluation of semen quality is crucial for predicting fertility success in artificial insemination and eventual rooster selection within poultry breeding programs. However, the multitude of parameters obtained in semen quality analysis makes it challenging for breeders to make informed selection decisions. This study evaluated semen samples from 210 roosters in seven chicken breeds, using a computer-aided sperm analysis (CASA) system. A multivariate approach utilizing factor analysis (FA) was applied to simplify the data. The FA condensed 14 semen quality traits into 3 factors, linearity factor, velocity factor, and quantitative factor, explaining 75.82% of the original variations. The Beijing-You breed was selected to analyze the association between fertility and these semen quality factors, and we found high correlation between fertility and quantitative (r = 0.84) and linearity (r = 0.63) factors, and low correlation with the velocity factor (r = 0.19). Based on individual factor scores, breed clustering revealed distinct profiles with Houdan, Tibetan, and White Leghorn demonstrating lower sperm counts and poor linearity. Columbian Plymouth Rock exhibited high speed with poor linearity while Beijing-You, Rhode Island Red, and Barred Plymouth Rock displayed higher sperm counts with compromised speed and linearity. This study demonstrates that FA effectively consolidates multiple semen quality traits into fewer, biologically relevant factors. These findings provide valuable insights into breed-specific reproductive characteristics and offer actionable information for optimizing breeding in poultry production. Full article

Mortality from Marek’s disease virus (MDV) infection results in economic loss for the poultry industry. It is controlled by vaccination, but the virus mutates and becomes more virulent. Variation within the MHC is well known to impact the outcomes following MDV infection from research performed utilizing the White Leghorn breed, with laboratory strains of the virus. The effect of the MHC haplotype following MDV challenge was determined from six lines of commercial elite (White Plymouth Rock (two), White Leghorn (three), and Rhode Island Red (one)) egg layer lines, challenged with vv+ virus. Mortality was recorded as sire daughter averages at 16–18 weeks of age from 19 generations of data. Sires were genotyped using a set of MHC-specific SNPs, encompassing 210,000 bp. Across all lines, there was a total of 23 unique MHC haplotypes, of which 15 were found at a frequency greater than 5% and used for further analysis. A significant impact on mortality was found for 16 of the haplotypes, with 9 haplotypes associated with decreased mortality and 7 haplotypes with increased mortality. There were three haplotypes identified in more than one line, allowing cross-line comparisons. The effect of these common haplotypes was consistent (either negative, positive or neutral) between lines. Full article

This study aimed to evaluate the effects of dietary 5-aminolevulinic acid (ALA) on laying hens to alleviate chronic heat stress-induced renal damage, resulting in improved egg productivity and eggshell quality. A total of 57 white-leghorn laying hens (46 weeks old) were randomly assigned to three groups and fed three experimental diets with different levels of ALA (0, 10, and 100 ppm) for 1 week. The birds in each group were then divided into two subgroups; one of the two subgroups was subjected to heat stress (33 °C for 3 weeks), whereas the other group was maintained at 24 °C. Heat exposure significantly decreased the laying rate and eggshell strength and caused renal damage, whereas ALA supplementation alleviated heat-induced poor productivity and renal damage. ALA increased the renal mitochondrial DNA copy number and downregulated the expression of the cGAS-STING pathway-related genes in the kidneys of heat-stressed hens. Furthermore, ALA upregulated the renal expression levels of NRF2 and HO-1, whereas it downregulated those of NF-κB and tended to decrease the content of TBARS in the kidney (p = 0.07). Dietary ALA confers a renal protective effect by reducing heat-induced mitochondrial damage and enhancing antioxidant activity, which may contribute to improved productivity under chronic heat stress. Full article

Maintaining genetic diversity is vital for biodiversity and livestock sustainability, with monitoring serving as a prerequisite for conservation strategies. As an initial step for developing future strategies, we analysed the genetic diversity and conservation priorities of 16 chicken breeds managed by a government institute in this study. The breeds were classified as native or locally adapted per FAO definitions and grouped by origin (i.e., governmental or private farms). Genetic diversity, assessed through observed and expected heterozygosity, inbreeding coefficients, and linkage disequilibrium, was high in native breeds from government institutions, such as Chungnam White Korean Native (CNW) and Gangwon Black Korean Native (GWL). Private farm breeds, including Hoeungseong-Yakdak (HYD), exhibited lower diversity. Conservation priorities based on contributions to total genetic diversity (HT) and allelic diversity (AT) revealed that locally adapted breeds, such as Cornish (S) and White Leghorn, significantly contributed to HT. Native breeds, such as CNW and Hyuin black, had higher contributions to AT. Combined assessments indicated that S, CNW, and GWL have the highest conservation priorities. Despite lower rankings, unique breeds such as HYD require targeted conservation owing to their distinctiveness. In conclusion, Korean chicken breeds such as S, CNW, and GWL are vital for maintaining genetic diversity among government-managed breeds. Full article

The cytokines IFN-γ and CD154 have been well established, and they play pivotal roles in immune protection against Salmonella in mice, but their effects and specific mechanisms in Salmonella-infected chickens are less understood. In this study, we conducted animal experiments to screen the highly immunoprotective chIFN-γ-chCD154 fusion protein compared with single protein chIFN-γ or chCD154 in white Leghorn chickens. The results showed that compared with separate pretreatments with chIFN-γ and chCD154, the fusion protein, chIFN-γ-chCD154, synergistically increased survival of infected chickens, reduced bacterial load in feces and organs, and attenuated pathological damage to the liver and cecum. Pretreatment with chIFN-γ-chCD154 also increased humoral immune responses, expression of the tight junction proteins zo-1, occludin, and claudin-1, and the relative abundance of Enterococcus_cecorum, Lactobacillus_helveticus, and Lactobacillus_agilis, which protect against intestinal inflammation. Compared with single protein pretreatment, chIFN-γ-chCD154 significantly upregulated STAT1, IRF1, and GBP1 in infected chickens while decreasing mRNA expression of TLR4, MyD88, NF-κB, TNF-α, IL-6, and IL-1β. In summary, damage to the cecal epithelial barrier and the inflammation induced by S. typhimurium infection was alleviated by chIFN-γ-chCD154 pretreatment through a mechanism involving the TLR4/MyD88/NF-κB and IFN-γ/STAT/IRF1/GBP1 pathways. Full article

Understanding genetic diversity, runs of homozygosity (ROH), and selection signatures is critical for the conservation and breeding management of native Japanese chickens. In this study, genetic diversity, ROH, and selection signatures in 11 populations of seven native Japanese breeds and three foreign breeds with different genetic and behavioral backgrounds were investigated using 11,493 SNPs identified through restriction-site-associated DNA sequencing. The Oh-Shamo (OSM), an aggressive cockfighting breed, exhibited the highest genetic diversity. Six native Japanese breeds, Ingie (IG), Ryujin-Jidori (RYU), Tosa-Jidori (TJI), Tosa-Kukin (TKU), Nagoya (NAG), and Ukkokei (UK), showed intermediate levels of genetic diversity and ROH. Population analyses grouped the 11 populations into four distinct clusters: (1) five populations comprising three foreign breeds (the Fayoumi inbred line, closed-colony G line of White Leghorn, commercial T line of WL, and White Plymouth Rock) and the IG Japanese breed; (2) OSM and two old Jidori breeds (RYU and TJI); (3) TKU and UK; and (4) the meat-type Nagoya breed. ROH and Fst analyses identified seven SNPs on chromosomes 13, 17, 20, 24, and 26, five of which were candidate genetic variants for fear-related behavior. These findings provide insights into genetic diversity and conserved genomic segments valuable for breeding and conservation in Japanese chicken breeds. Full article

Russian Snow White (RSW) chickens are characterized by high egg production, extreme resistance to low temperatures, disease resistance, and by the snow-white color of the day-old chicks. Studying the genome of this unique chicken breed will reveal its evolutionary history and help to understand the molecular genetic mechanisms underlying the unique characteristics of this breed, which will open new breeding opportunities and support future studies. We have sequenced and made a de novo assembly of the whole RSW genome using deep sequencing (250×) by the short reads. The genome consists of 40 chromosomes with a total length of 1.1 billion nucleotide pairs. Phylogenetic analysis placed the RSW near the White Leghorn, Fayoumi, and Houdan breeds. Comparison with other chicken breeds revealed a wide pool of mutations unique to the RSW. The functional annotation of these mutations showed the adaptation of genes associated with the development of the nervous system, thermoreceptors, purine receptors, and the TGF-beta pathway, probably caused by selection for low temperatures. We also found adaptation of the immune system genes, likely driven by selection for resistance to viral diseases. Integration with previous genome-wide association studies (GWAS) suggested several causal single nucleotide polymorphisms (SNPs). Specifically, we identified an RSW-specific missense mutation in the RALYL gene, presumably causing the snow-white color of the day-old chicks, and an RSW-specific missense mutation in the TLL1 gene, presumably affecting the egg weight. Full article