Leghorn Lines Research Articles

Comparing performance, morphological, physical, and chemical properties of eggs produced by 1940 Leghorn or a commercial 2016 Leghorn fed representative diets from 1940 to 2016

Eggshell quality is one of the most significant factors affecting the egg industry as it economically influences the quantity of saleable eggs. Eggshell quality can be improved through optimization of genotype, housing system, and mineral nutrition. This study aimed to compare genotypes and evaluate the morphological, physical, and chemical properties of eggs (weight, breaking strength, Haugh units, and dry matter) by hens of two different strains fed a 1940 and 2016 representative diet. Egg production was measured daily and there were four periods with 10-wk intervals in which eggs were analyzed starting at 30 wk and ending at 60 wk of age measuring quality parameters. This study was set as a 2 × 2 factorial. The factors consisted of 2 leghorn genetic strains that were a 2016 commercial layer (W36) and a 1940 random-bred leghorn line, then 2 diets based on 2016 and 1940 dietary standards. The treatment groups: 1) 2016 hen on 1940 diet, 2) 2016 hen on 2016 diet, 3) 1940 hen on 1940 diet, and 4) 1940 hen on 2016 diet had 8 replicates with 10 hens per treatment housing 2 hens per cage. Body weights were higher in the 2016 hens when compared to the 1940 hens, however, the feed conversion ratio fluctuated in hens with the 2016 hens on the 1940 diet consuming the most feed throughout the majority of the trial. The 1940s hens came into production later than the 2016 hens; however, the rate of production was consistent with one another. Oviduct and ovary weights were heavier in the 2016 hens when compared to the 1940 hens. Egg quality, both interior and exterior was greater in the 2016 hens when compared to the 1940 hens. Parameters measured demonstrated significant differences (P ≤ 0.05) among treatment groups suggesting that genetics and nutrition both played a role in production rate and egg quality.

Epigenetic Factor MicroRNAs Likely Mediate Vaccine Protection Efficacy against Lymphomas in Response to Tumor Virus Infection in Chickens through Target Gene Involved Signaling Pathways.

Epigenetic factors, including microRNAs (miRNAs), play an important role in affecting gene expression and, therefore, are involved in various biological processes including immunity protection against tumors. Marek's disease (MD) is a highly contagious disease of chickens caused by the MD virus (MDV). MD has been primarily controlled by vaccinations. MD vaccine efficacy might, in part, be dependent on modulations of a complex set of factors including host epigenetic factors. This study was designed to identify differentially expressed miRNAs in the primary lymphoid organ, bursae of Fabricius, in response to MD vaccination followed by MDV challenge in two genetically divergent inbred lines of White Leghorns. Small RNA sequencing and bioinformatic analyses of the small RNA sequence reads identified hundreds of miRNAs among all the treatment groups. A small portion of the identified miRNAs was differentially expressed within each of the four treatment groups, which were HVT or CVI988/Rispens vaccinated line 63-resistant birds and line 72-susceptible birds. A direct comparison between the resistant line 63 and susceptible line 72 groups vaccinated with HVT followed by MDV challenge identified five differentially expressed miRNAs. Gene Ontology analysis of the target genes of those five miRNAs revealed that those target genes, in addition to various GO terms, are involved in multiple signaling pathways including MAPK, TGF-β, ErbB, and EGFR1 signaling pathways. The general functions of those pathways reportedly play important roles in oncogenesis, anti-cancer immunity, cancer cell migration, and metastatic progression. Therefore, it is highly likely that those miRNAs may, in part, influence vaccine protection through the pathways.

Identification of the Immunoglobulin Light Chain Alleles in White Leghorn Line 15I5×71

Identification of the Immunoglobulin Light Chain Alleles in White Leghorn Line 15I5×71

Differences in the microbiome of the small intestine of Leghorn lines divergently selected for antibody titer to sheep erythrocytes suggest roles for commensals in host humoral response.

For forty generations, two lines of White Leghorn chickens have been selected for high (HAS) or low (LAS) antibody response to a low dose injection of sheep red blood cells (SRBCs). Their gut is home to billons of microorganisms and the largest number of immune cells in the body; therefore, the objective of this experiment was to gain understanding of the ways the microbiome may influence the differential antibody response observed in these lines. We achieved this by characterizing the small intestinal microbiome of HAS and LAS chickens, determining their functional microbiome profiles, and by using machine learning to identify microbes which best differentiate HAS from LAS and associating the abundance of those microbes with host gene expression. Microbiome sequencing revealed greater diversity in LAS but statistically higher abundance of several strains, particularly those of Lactobacillus, in HAS. Enrichment of microbial metabolites implicated in immune response such as lactic acid, short chain fatty acids, amino acids, and vitamins were different between HAS and LAS. The abundance of several microbial strains corresponds to enriched host gene expression pathways related to immune response. These data provide a compelling argument that the microbiome is both likely affected by host divergent genetic selection and that it exerts influence on host antibody response by various mechanisms.

Evaluating the Ileal and Cecal Microbiota Composition of a 1940 Heritage Genetic Line and a 2016 Commercial Line of white Leghorns Fed Representative Diets from 1940 to 2016

This study identified and evaluated differences between microbiome compositions of the ileum and ceca of 1940 and 2016 white leghorn genetic strains fed representative contemporary diets from those times. Ileal and cecal samples were collected at 69 weeks of age. Alpha and beta diversity metrics were generated, and the Analysis of Composition of Microbiomes (ANCOM) was utilized to determine significantly different taxa. Ileum and ceca alpha diversity were significantly different (p = 0.001; Q = 0.001); however, no differences between genetic lineage were observed (p > 0.05; Q > 0.05). Beta diversity between the ileum and ceca and the genetic lines was significantly different (p = 0.001; Q = 0.001). The ANCOM of the ileum showed significant differences between Proteobacteria and Actinobacteriota phyla (p ˂ 0.05) and significant differences between Pseudomonas, Rhizobiaceae, Leuconostoc, and Aeriscardovia genera (p ˂ 0.05). For ceca ANCOM, Proteobacteria, Firmicutes, Actinobacteriota, and Euryarchaeota phyla were significantly different (p ˂ 0.05), with Firmicutes having the highest relative abundance across all groups, and there were significant differences in genera Pseudomonas, Leuconostoc, Alloprevotella, and Aeri scardovia, with Alloprevotella having the highest relative abundance. The results suggest that genetic makeup in conjunction with the nutritional composition influences the cecal and ileal microbiota of corresponding hens.

Identification of methylation pattern in the partial promoter of acetyl CoA carboxylase beta (ACACB) gene in White Leghorn line

The present study was initiated with an objective of identifying methylation pattern in the partial promoter of Acetyl CoA carboxylase beta (ACACB) gene in White Leghorn IWK line. To understand the epigenetic regulation of gene expression, birds with highest and lowest expression at 18th week and 40th week age were chosen. Epigenetic profile of the minimal promoter indicated that there were seven CpG islands in this region, positioned at 75, 87, 155, 269, 284, 311 and 426 positions of the 555 bp promoter region. Among these, except the position 75, the remaining positions showed cis-acting transcription factors. There was negative relationship between highest and lowest expressed birds with the per cent methylation in White Leghorn IWK line. The mean methylation per cent was found to be 42.85 and 21.42 at 18th and 40th weeks of age, respectively. The results indicated decrease in methylation per cent with age. The overall mean methylation per cent of 32.14 was observed.

Pathogenicity of goose astrovirus genotype 2 in chickens

Goose astrovirus genotype 2 (GAstV-2) is the causative agent causing severe visceral gout and joint gout in goslings, with mortality rates of affected flocks up to 50%. To date, continuous GAstV-2 outbreaks still pose a great threat to goose industry in China. Although most researches on GAstV-2 have focused on its pathogenicity to geese and ducks, limited studies have been performed on chickens. Herein, we inoculated 1-day-old specific pathogen-free (SPF) White Leghorn line chickens with 0.6 mL of GAstV-2 culture supernatant (TCID50 10-5.14/0.1 mL) via orally, subcutaneously and intramuscularly, and then assessed the pathogenicity. The results revealed that the infected chickens presented depression, anorexia, diarrhea, and weight loss. The infected chickens also suffered from extensive organ damage and had histopathological changes in the heart, liver, spleen, kidney, and thymuses. The infected chickens also had high viral load in tissues and shed virus after the challenge. Overall, our research demonstrates that GAstV-2 can infect chickens and adversely affect the productivity of animals. And the viruses shed by infected chickens can pose a potential risk to the same or other domestic landfowls.

MicroRNAs with non-additive expression in the ovary of hybrid hens target genes enriched in key reproductive pathways that may influence heterosis for egg laying traits.

Heterosis has been extensively exploited in chicken breeding to improve laying traits in commercial hybrid stock. However, the molecular mechanisms underlying it remains elusive. This study characterizes the miRNAome in the pre-hierarchical follicles of purebred and hybrid laying hens, and investigate the functions of miRNAs with non-additive expression in the pre-hierarchical follicles as they modulate heterosis for egg number and clutch size. To achieve that aim, White Leghorn and Rhode Island Red chicken lines were reciprocally crossed to generate hybrids. The crossbreds demonstrated heterosis for egg number and clutch size, and pre-hierarchical follicles from 4 birds of each genotype were collected at 53 weeks of age. Mode of miRNA expression was characterized after miRNA sequencing. A total of 50 miRNAs including 30 novel ones, were found to exhibit non-additive expression. Dominance was the predominant mode of expression exhibited by majority of the miRNAs. Functional analysis of target genes of the known miRNAs with non-additive expression revealed Gene Ontology terms related to regulation of transcription, metabolic processes and gene expression. KEGG and REACTOME pathways including hedgehog, cellular senescence, wnt, TGF-β, progesterone-mediated oocyte maturation, oocyte meiosis, GnRH signaling, signal transduction and generic transcription, which can be linked to primordial follicle activation, growth and ovulation, were significantly enriched by target genes of miRNAs with non-additive expression. Majority of the genes enriched in these biological pathways were targeted by gga-miR-19a, gga-miR-19b, gga-miR-375, gga-miR-135a, and gga-miR-7 and 7b, thus, revealing their synergistic roles in enhancing processes that could influence heterosis for egg number and clutch size in hybrid hens.

Using egg production longitudinal recording to study the genetic background of resilience in purebred and crossbred laying hens

BackgroundThere is growing interest in using genetic selection to obtain more resilient farm animals (i.e. that are minimally affected by disturbances or rapidly recover from them). The aims of this study were to: (i) estimate the genetic parameters of resilience indicator traits based on egg production data, (ii) assess whether these traits are genetically correlated in purebreds and crossbreds, and (iii) assess the genetic correlations of these traits with egg production (EP) as total number of eggs between 25 and 83 weeks. Purebred hens (33,825 from a White Leghorn (WA) line and 34,397 from a Rhode Island (BD) line were housed in individual cages, while crossbred hens were housed in collective cages of 6 to 8 paternal half-sibs (12,852 WA and 3898 BD crossbred groups, where the name of the group refers to the line used as the sire). Deviations of a hen’s weekly egg production from the average of the corresponding batch were calculated. Resilience indicator traits investigated were the natural logarithm of the variance (LNVAR), the skewness (SKEW), and the lag-one autocorrelation (AUTO-R) of these deviations.ResultsIn both purebred lines, EP was estimated to be lowly heritable (WA: 0.11 and BD: 0.12). Resilience indicators were also estimated to be lowly heritable in both lines (LNVAR: 0.10 and 0.12, SKEW: 0.04 and 0.02, AUTO-R: 0.06 and 0.08 in WA and BD, respectively). In both crossbred groups, EP, AUTO-R, and SKEW were estimated to be less heritable than in purebreds (EP: h^{2} ≤ 0.07; and resilience indicator traits: h^{2} ≤ 0.03), while LNVAR had an h^{2} estimate that was similar to or higher in crossbreds (h^{2} ranged from 0.13 to 0.21) than in purebreds. In both purebreds and crossbreds, resilience indicator traits were estimated to have favorable genetic correlations with EP and between each other. For all traits and in both lines, estimates of genetic correlations between purebreds and crossbreds (r_{pc}) differed from 1 and ranged from 0.16 to 0.63.ConclusionsThese results show that selection for resilience based on EP data can be considered in breeding programs for layers. Genetic improvement of resilience in crossbreds can be achieved by using information on purebreds, but would be greatly enhanced by the integration of information on crossbreds in breeding programs.

Mitochondrial and Glycolytic Capacity of Peripheral Blood Mononuclear Cells Isolated From Diverse Poultry Genetic Lines: Optimization and Assessment.

Cellular metabolic preference is a culmination of environment, nutrition, genetics, and individual variation in poultry. The Seahorse XFe24 analyzer was used to generate foundational immune cellular metabolic data in layer, broiler, and legacy genetic strains using fresh chicken peripheral blood mononuclear cells (PBMCs). Baseline mitochondrial respiration [oxygen consumption rate (OCR)] and glycolytic activity [extracellular acidification rate (ECAR)] were determined in modern commercial laying hen (Bovans White) and broiler (Ross 308) lines, as well as the highly inbred lines of Iowa State University (L8, Fayoumi M-15.2, Spanish, Ghs-6), partially inbred broiler line, and advanced intercrosses of broiler by Fayoumi M-15.2 and broiler by Leghorn lines. Commercial broiler vs. Bovans layer and unvaccinated vs. vaccinated Bovans layer immune cell metabolic potential were compared following an in-assay pathway inhibitor challenge. Titrations consistently showed that optimal PBMC density in laying hens and broilers was 3 million cells per well monolayer. Assay media substrate titrations identified 25 mM glucose, 1 mM glutamine, and 1 mM sodium pyruvate as the optimal concentration for layer PBMCs. Pathway inhibitor injection titrations in Bovans layers and broilers showed that 0.5 μM carbonyl cyanide-4 phenylhydrazone (FCCP) and 1 μM oligomycin were optimal. Baseline OCR and ECAR were significantly affected by genetic line of bird (p < 0.05), with the dual-purpose, L8 inbred line showing the highest OCR (mean 680 pmol/min) and the partially inbred broiler line showing the greatest ECAR (mean 74 mpH/min). ECAR metabolic potential tended to be greater in modern layers than broilers (p < 0.10), indicating increased ability to utilize the glycolytic pathway to produce energy. OCR was significantly higher in vaccinated than unvaccinated hens (p < 0.05), while baseline ECAR values were significantly lower in vaccinated Bovans laying hens, showing increased oxidative capacity in activated immune cells. These baseline data indicate that different genetic strains of birds utilized the mitochondrial respiration pathway differently and that modern commercial lines may have reduced immune cell metabolic capacity compared with legacy lines due to intense selection for production traits. Furthermore, the Seahorse assay demonstrated the ability to detect differences in cellular metabolism between genetic lines and immune status of chickens.

Study on performance traits of laying hens with crossing the White Leghorn and the Rhode Island breeds

The current steady increase in the global population is accompanied by a dramatic growth in demand for food, whose satisfaction relies heavily on animal protein sources. Poultry farming is already mankind’s key source of protein. Changes in consumer habits combined with the negative impacts of climate change are posing new challenges to poultry breeding companies today. Certain traits properties relating to egg production among offspring groups resulting from the crossing of the White Leghorn and the Rhode Island breeds show improvements relative to the corresponding properties of pure-bred offspring. This literature review is aimed at summing up experiments focusing on White Leghorn and Rhode Island crosses in terms of the main traits properties relating to egg production. Experiments involving the crossing of the White Leghorn and Rhode Island breeds tend to occur mainly during pure-bred poultry breeding. Studies discussing the performance of groups of offspring of White Leghorn (WL) and Rhode Island (RI) breeds, without analysing physiological types of experiments, have been few and far between in the past 20 years. Most of the few such studies originate from countries of the third world focusing in most cases on matters of feeding. This is explained, for the most part, by the fact that in the current period of modern poultry farming, only the world’s top breeding companies are in possession of high performance Leghorn and Rhode lines and they seldom ever publish scientific papers allowing glimpse into breeders’ development or strategic activities of breeders.

Cloning, characterisation and expression of the SERPINB14 gene, and association of promoter polymorphisms with egg quality traits in layer chicken

ABSTRACT 1. Ovalbumin (SERPINB14) is the most abundant protein present in egg white contributing about 54% of the total egg protein. In this study, the objectives were to clone and characterise the coding sequence of the SERPINB14 gene, to explore its expression profile, identify polymorphisms in the promoter of the gene and explore any association with egg quality traits in White Leghorn chickens. 2. SNPs and mRNA expression of SERPINB14 in White Leghorn chicken lines were detected by PCR-single strand conformation polymorphism (SSCP) along with sequencing and qPCR. The open reading frame (ORF) was cloned in an expression plasmid vector and sequenced. 3. The ORF of this gene was 1161 bp encoding a peptide of 386 amino acids. There were three SNPs observed in the coding region of the gene, one of which was of the mis-sense type, having c562G>A transition which resulted in substitution of alanine to threonine at position 188 in the protein sequence. In both the lines, an increase in expression of the gene was observed after onset of egg production with peak expression at the 40th week of age compared to before onset of lay. The SERPINB14 gene was expressed in the magnum, but not in ovary and infundibulum, tissues of each White Leghorn line. The promoter region of the gene showed SNPs with three haplotypes; H1, H2, and H3. The haplo groups were associated with the egg weight and age at sexual maturity in the IWI line and Haugh unit and albumin index in the IWK line. 4. It was concluded that the ORF of SERPINB14 gene in White Leghorn chicken lines is polymorphic. The promoter region of the gene is also polymorphic and has significant (P < 0.05) association with Haugh unit and egg weight in IWK and IWI chicken lines, respectively.

Induction of Chicken Host Defense Peptides within Disease-Resistant and -Susceptible Lines.

Host defense peptides (HDPs) are multifunctional immune molecules that respond to bacterial and viral pathogens. In the present study, bone marrow-derived cells (BMCs) and chicken embryonic fibroblasts (CEFs) were cultured from a Leghorn line (Ghs6) and Fayoumi line (M15.2), which are inbred chicken lines relatively susceptible and resistant to various diseases, respectively. The cells were treated by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly(I:C)) and, subsequently, mRNA expression of 20 chicken HDPs was analyzed before and after the stimulation. At homeostasis, many genes differed between the chicken lines, with the Fayoumi line having significantly higher expression (p < 0.05) than the Leghorn line: AvBD1, 2, 3, 4, 6, and 7 in BMCs; CATH1, CATH3, and GNLY in CEFs; and AvDB5, 8, 9, 10, 11, 12, 13 in both BMCs and CEFs. After LPS treatment, the expression of AvBD1, 2, 3, 4, 5, 9, 12, CATH1, and CATHB1 was significantly upregulated in BMCs, but no genes changed expression in CEFs. After poly(I:C) treatment, AvBD2, 11, 12, 13, CATHB1 and LEAP2 increased in both cell types; CATH2 only increased in BMCs; and AvBD3, 6, 9, 14, CATH1, CATH3, and GNLY only increased in CEFs. In addition, AvBD7, AvBD14, CATH1, CATH2, GNLY, and LEAP2 showed line-specific expression dependent upon cell type (BMC and CEF) and stimulant (LPS and poly(I:C)). The characterization of mRNA expression patterns of chicken HDPs in the present study suggests that their functions may be associated with multiple types of disease resistance in chickens.

Liver Transcriptome Responses to Heat Stress and Newcastle Disease Virus Infection in Genetically Distinct Chicken Inbred Lines.

Heat stress results in reduced productivity, anorexia, and mortality in chickens. The objective of the study was to identify genes and signal pathways associated with heat stress and Newcastle disease virus (NDV) infection in the liver of chickens through RNA-seq analysis, using two highly inbred chicken lines (Leghorn and Fayoumi). All birds were held in the same environment until 14 days of age. On day 14, half the birds were exposed to 38 °C with 50% relative humidity for 4 h, then 35 °C until the end of the experiment. The remaining birds were kept at 25 °C throughout the experiment. The heat-treated birds were inoculated at 21 days of age with 107 EID50 (One EID50 unit is the amount of virus that will infect 50 percent of inoculated embryos) NDV La Sota strain to investigate the effects of both heat stress and NDV infection. Physiological parameters were recorded as blood phenotypes at three stages: acute heat (AH), chronic heat (CH1), and chronic heat combined with NDV infection (CH&NDV), at 4 h, 7 days, and 10 days post-initiation of heat treatment, respectively. Our previous work revealed that the heat-resilient Fayoumi line maintained a more stable acid-base balance in their blood compared to the Leghorn line. Liver samples were harvested on both AH and CH&NDV to characterize the transcriptome profiles of these two inbred lines. Both genetic lines and treatments had large impact on the liver transcriptome. Fayoumi birds had more differentially expressed genes (DEGs) than Leghorn birds for both treatments. Metabolic and immune-related genes were on the DEG list, with Fayoumi having more immune-related DEGs than Leghorns, which was confirmed by gene functional enrichment analysis. Weighted correlation network analysis (WGCNA) indicated that the driver genes such as Solute Carrier Family genes could be very important for stabilizing the acid-base balance in Fayoumi birds during heat stress. Therefore, candidate genes such solute carrier family genes could be potential genetic targets that are regulated by Fayoumis to maintain physical hemostasis under heat stress. Differential gene expression showed that Leghorns mainly performed metabolic regulation in response to heat stress and NDV infection, while Fayoumis regulated both immune and metabolic functions. This study provides novel insights and enhances our understandings of liver response to heat stress of heat resilient and susceptible inbred chicken lines.

Identification of single nucleotide polymorphism in heat shock protein HSP70 and HSP90 after four selection generations in two lines of chickens

Climatic changes have affected the entire world resulting in high temperatures, consequently leading to a negative impact on poultry production. Therefore, we conducted this study to detect the single nucleotide polymorphisms (SNPs), which is responsible for producing heat shock protein HSP70 and HSP90 in two selected lines of chicken, Dandarawi and Leghorn that were formally selected for four generations, for achieving a better growth rate under heat pressure. At age 16 weeks, body weight and body measurements were evaluated for Dandarawi and Leghorn males. mRNA levels of HSP70 and HSP90 genes were measured, and the polymorphism of these two genes was examined via DNA sequencing. Results showed that after four generations under heat stress conditions, the Dandarawi and Leghorn lines of chicken were distinguishable in terms of body weight and body measurements. Additionally, HSP70 and HSP90 a highly significant increase in gene expression for the Dandarawi line compared to the Leghorn line. These results indicate that the Dandarawi breed has genes that enable it to adapt under hot climate conditions. Hence, when selected to increase production under high temperatures, the gene expression is twice that of the Leghorn strain under the same conditions of selection. The Dandarawi chicken had better heat tolerance than the Leghorn chicken. The difference was observed on chromosome 5 in the region 52784621: 52784671 in exon 1 in HSP70 that was caused by the amino acid cysteine instead of arginine because of the substitution of T nucleotide with C, indicating the alteration in the gene expression level of HSPs. Therefore, we recommend using chromosome 5 in the region 52784621: 52784671 in exon 1 in HSP70 as a candidate gene in selection programs for evaluating heat stress tolerance.

Production of Germ-Free Fast-Growing Broilers from a Commercial Line for Microbiota Studies.

Studies of the gut microbiota contribution to the host physiology and immunocompetence are facilitated by the availability of germ-free animal models, which are considered the gold standard. Nesting birds are ideal models for the production of germ-free animals since there is no need to raise their relatives under sterile conditions. Germ-free chickens are mainly generated from specific-pathogen-free (SPF) experimental lines, which are poorly representative of commercial chicken lines.The method proposed here allowed the production of germ-free chickens from the fast growing broiler line Ross PM3, commonly used by the poultry industry.Eggs were quickly collected after laying at a broiler breeder farm.They underwent a strict decontamination process from the collection to the introduction in a sterile egg hatching isolator.The chicks have been hatched and kept in these sterile isolators during the period necessary to control their sterility. Originally developed for an experimental SPF white leghorn line, the present protocol has been adapted not only to the Ross PM3 broiler line but also to quails. It therefore represents a robust and readily adaptable procedure to other poultry species and nesting birds of economic, biological or ecological relevance.

Genetic responses of inbred chicken lines illustrate importance of eIF2 family and immune-related genes in resistance to Newcastle disease virus

Newcastle disease virus (NDV) replication depends on the translation machinery of the host cell; therefore, the eukaryotic translation initiation factor 2 (eIF2) gene family is a likely candidate for control of viral replication. We hypothesized that differential expression of host genes related to translation and innate immune response could contribute to differential resistance to NDV in inbred Fayoumi and Leghorn lines. The expression of twenty-one genes related to the interferon signaling pathway and the eIF2 family was evaluated at two- and six-days post infection (dpi) in the spleen from both lines, either challenged by NDV or nonchallenged. Higher expression of OASL in NDV challenged versus nonchallenged spleen was observed in Leghorns at 2 dpi. Lower expression of EIF2B5 was found in NDV challenged than nonchallenged Fayoumis and Leghorns at 2 dpi. At 2 dpi, NDV challenged Fayoumis had lower expression of EIF2B5 and EIF2S3 than NDV challenged Leghorns. At 6 dpi, NDV challenged Fayoumis had lower expression of EIF2S3 and EIF2B4 than NDV challenged Leghorns. The genetic line differences in expression of eIF2-related genes may contribute to their differential resistance to NDV and also to understanding the interaction between protein synthesis shut-off and virus control in chickens.

Accuracy of genomic prediction of shell quality in a White Leghorn line

Several genomic methods were applied for predicting shell quality traits recorded at 4 different hen ages in a White Leghorn line. The accuracies of genomic prediction of single-step GBLUP and single-trait Bayes B were compared with predictions of breeding values based on pedigree-BLUP under single-trait or multitrait models. Breaking strength (BS) and dynamic stiffness (Kdyn) measurements were collected on 18,524 birds from 3 consecutive generations, of which 4,164 animals also had genotypes from an Affymetrix 50K panel containing 49,591 SNPs after quality control edits. All traits had low to moderate heritability, ranging from 0.17 for BS to 0.34 for Kdyn. The highest accuracies of prediction were obtained for the multitrait single-step model. The use of marker information resulted in higher prediction accuracies than pedigree-based models for almost all traits. A genome-wide association study based on a Bayes B model was conducted to detect regions explaining the largest proportion of genetic variance. Across all 8 shell quality traits analyzed, 7 regions each explaining over 2% of genetic variance and 54 regions each explaining over 1% of genetic variance were identified. The windows explaining a large proportion of genetic variance overlapped with several potential candidate genes with biological functions linked to shell formation. A multitrait repeatability model using a single-step method is recommended for genomic evaluation of shell quality in layer chickens.

Dietary fiber content affects growth, body composition, and feed intake and their associations with a major growth locus in growing male chickens of an advanced intercross population

In this study, we examined the effect of different dietary fiber concentrations on growth, body composition, and feed efficiency of growing male chickens with different genetic background. We tested whether the single nucleotide polymorphisms (SNP) in a previously identified growth locus on chromosome 4 (GGA4) between 69.3 and 77.9 Mb was associated with the traits of biologic and commercial importance in interaction with the diet. The study was conducted with growing male chickens of generation 12 of an advanced intercross population descending from the initial cross between inbred New Hampshire (high-growth) and White Leghorn (low-growth) lines. We performed a 2-way interaction analysis between the dietary fiber content and SNP genotypes. At wk 4, the growing male chickens were randomly divided into 2 diet treatments, which were housed and fed individually with either a low- (LFD, n = 38) or a high-fiber diet (HFD, n = 41) containing 0.8 and 5% lignocellulose with a crude fiber content of 60%, respectively. Body weights were recorded weekly. Body composition was examined at wk 13. Feed intake and excreta were analyzed at wk 6 and 13. The effect of dietary fiber content on body weight gain and feed intake was age-dependent. The feed conversion ratio was not altered. Feeding HFD resulted in 10% greater body weight gain (P = 0.047) and greater feed intake (P = 0.014) than LFD at wk 6. At wk 13, the visceral adipose tissue mass was 38% lower (P = 0.008) and the gizzard mass was 14% greater (P = 0.012). The reduction of total fat content in adipose tissue (P = 0.039) in the HFD was associated with reduced intramuscular fat content in drumsticks-thighs (4.2 vs. 5.1%, P = 0.004). The SNP genotypes at the GGA4 locus interacted with dietary fiber content and influenced body weight gain (P = 0.042), visceral adipose tissue mass (P ≤ 0.029), and feed intake (P ≤ 0.050). The New Hampshire alleles of SNPs on GGA4 led to increased body weight gain and feed intake (P ≤ 0.050), and tended to reduced fat deposition under HFD. Our data indicate that the addition of lignocellulose to the diet would improve productivity and carcass quality through reduced adipose tissue mass without changes in feed efficiency. Furthermore, our findings provide evidence for interaction of the target GGA4 region with dietary fiber usage affecting growth, fat deposition, and feed intake. The particular GGA4 locus may contain a single or several genes associated with growth, body composition, and feed intake.

Innate Immune Genes Associated With Newcastle Disease Virus Load in Chick Embryos From Inbred and Outbred Lines.

Newcastle disease virus (NDV) causes substantial economic losses to smallholder farmers in low- and middle-income countries with high levels of morbidity and mortality in poultry flocks. Previous investigations have suggested differing levels of susceptibility to NDV between specific inbred lines and amongst breeds of chickens, however, the mechanisms contributing to this remain poorly understood. Studies have shown that some of these differences in levels of susceptibility to NDV infection may be accounted for by variability in the innate immune response amongst various breeds of poultry to NDV infection. Recent studies, in inbred Fayoumi and Leghorn lines, uncovered conserved, breed-dependent, and subline-dependent responses. To better understand the role of innate immune genes in engendering a protective immune response, we assessed the transcriptional responses to NDV of three highly outbred Tanzanian local chicken ecotypes, the Kuchi, the Morogoro Medium, and the Ching’wekwe. Hierarchical clustering and principal coordinate analysis of the gene expression profiles of 21-day old chick embryos infected with NDV clustered in an ecotype-dependent manner and was consistent with the relative viral loads for each of the three ecotypes. The Kuchi and Morogoro Medium exhibit significantly higher viral loads than the Ching’wekwe. The results show that the outbred ecotypes with increased levels of expression of CCL4, NOS2, and SOCS1 also had higher viral loads. The higher expression of SOCS1 is inconsistent with the expression in inbred lines. These differences may uncover new mechanisms or pathways in these populations that may have otherwise been overlooked when examining the response in highly inbred lines. Taken together, our findings provide insights on the specific conserved and differentially expressed innate immune-related genes involved the response of highly outbred chicken lines to NDV. This also suggests that several of the specific innate immunity related genes identified in the current investigation may serve as markers for the selection of chickens with reduced susceptibility to NDV.