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Phosphorus (P) is an essential mineral for all forms of life including laying hens, playing a crucial role in growth and efficient egg production. Recent studies suggest that current P recommendations might exceed the physiological demand, leading to unnecessarily high P excretions. This study on Lohmann Brown (LB) and Lohmann Selected Leghorn (LSL) laying hens (n=80; 10 replicates per strain, production period, and dietary group) investigates transcriptional changes in the jejunum, a critical intestinal segment for mineral absorption, in response to a diet either without (P-) or with (P+) a mineral supplement from monocalcium phosphate, administered over a 4-week period during the transition (15-19 weeks) or onset of laying (20-24 weeks). DESeq2 analysis of RNA sequencing data revealed that most differentially expressed genes (DEGs) varied between strains and age groups, with less pronounced effects from dietary mineral P content. The 19-week-old LB hens showed a stronger response to dietary mineral P removal, with transcripts affiliated with increased adaptation of the metabolism and decreased immune pathway activation. The identified pathways such as folate biosynthesis and p53 signaling, potentially link altered energy and amino acid metabolism (2-oxocarboxylic acid and arginine). Interestingly, genes involved in calcium transport (CALB1) and cellular signaling (PRKCA, STEAP4) along with tight junctions (CLDN2) were affected by complete removal of mineral P supplements, suggesting a promoted intestinal mineral uptake. Transcriptional regulation in the jejunum in response to low dietary mineral content is strain-specific when the laying phase begins, which may contribute to a physiological Ca:P ratio., Competing Interests: Disclosures All authors declare no conflicts of interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to characterize intestinal phytate degradation and mineral utilization by 2 laying hen strains before and after the onset of egg laying using diets without or with a mineral phosphorus (P) supplement. One offspring of 10 roosters per strain (Lohmann Brown-classic [LB] and Lohmann LSL-classic [LSL]) was sacrificed before (wk 19) and after (wk 24) the onset of egg-laying activity and following 4 wk placement in a metabolic unit. Diets were corn-soybean meal-based and without supplemented P (P-) or with 1 g/kg supplemented P (P+) from monocalcium phosphate. In wk 19 and 24, the blood plasma and digesta of duodenum+jejunum and distal ileum were collected. The concentration of P in blood plasma was higher in hens fed P+ than P- (P < 0.001). In duodenum + jejunum and ileum content, the concentrations of InsP 6 , Ins(1,2,4,5,6)P 5 and Ins(1,2,3,4,5)P 5 were lower in P- than in P+ (P ≤ 0.009). In duodenum+jejunum, the concentrations of InsP 6 , Ins(1,2,4,5,6)P 5 and Ins(1,2,3,4,5)P 5 were lower in wk 24 than 19 and lower in LSL than LB hens (P < 0.001). The concentration of myo-inositol (MI) in duodenum + jejunum content was lower in wk 19 than 24 (P < 0.001). Following a 4-d total excreta collection, the retained amount of P was higher in P+ than P- (P < 0.001). Phosphorus retention was lower in LB hens fed P- than in other treatments (P × strain: P = 0.039). In the jejunal tissue, some genes related to intracellular InsP metabolism were higher expressed in LB than LSL hens. The renunciation of mineral P increased endogenous phytate degradation, but more P was retained with supplemented P. Differences in endogenous phytate degradation between the periods before and after the onset of egg laying might be attributed to different Ca concentrations in intestinal digesta caused by different Ca needs in both periods., Competing Interests: DISCLOSURES MFö received speaker fees from Kyowa Kirin without relevance to this study. The authors declare they have no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

A comprehensive characterization of regulatory elements in the chicken genome across tissues will have substantial impacts on both fundamental and applied research. Here, we systematically identified and characterized regulatory elements in the chicken genome by integrating 377 genome-wide sequencing datasets from 23 adult tissues. In total, we annotated 1.57 million regulatory elements, representing 15 distinct chromatin states, and predicted about 1.2 million enhancer-gene pairs and 7662 super-enhancers. This functional annotation of the chicken genome should have wide utility on identifying regulatory elements accounting for gene regulation underlying domestication, selection, and complex trait regulation, which we explored. In short, this comprehensive atlas of regulatory elements provides the scientific community with a valuable resource for chicken genetics and genomics.

Phosphorus (P) inclusion in broiler diets needs to meet the physiological demands at a specific developmental stage to ensure the performance, health, and welfare of the birds and minimize nutrient losses. Toward a more efficient utilization of P in broiler husbandry, a timed nutritional conditioning strategy might enhance the endogenous mechanisms of mineral homeostasis and thus reduce dietary P supply of mineral sources. In this study, following a variable P supply in the starter phase, the effects of a dietary P depletion of broiler chickens were investigated at different developmental stages. Physiological adaptation mechanisms were elucidated based on zootechnical performance, endocrine parameters, regulation of intestinal P transport, bone characteristics, and health aspects. The results revealed a marked response to P depletion at the earliest developmental phase, after which indications of effective compensatory mechanism were detectable with advancing ages. Potential mechanisms that enable broilers to maintain mineral homeostasis primarily include endocrine control mediated by calcitriol actions, as well as intestinal P uptake and mineral mobilization from the bone. Conclusively, the precise timing, duration, and extent of a P depletion strategy in the broiler chicken might be considered for optimized nutrient utilization., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

There is growing evidence of the importance of miRNAs for intestinal functional properties and nutritional uptake. Comparative miRNAs profiles of the jejunal mucosa were established against two genetic backgrounds (Lohmann Brown-Classic (LB) and Lohmann LSL-Classic (LSL), which are similar in egg production but differ in physiological traits including mineral utilization, along the production periods of laying hens. The target genes of miRNAs higher expressed in LB vs. LSL (miR-126-3p, miR-214, miR-24-3p, miR-726-5p, miR-29b-3p) were enriched for energy pathways at all stages. The target genes of the miRNAs higher in LSL (miR-1788-5p, miR-103-3p, miR-22-5p, miR-221-3p, miR-375) were more enriched for immune and the bone signalling pathways. The most prominent expression differences were between 16 and 24 weeks of age before and after onset of laying. Our results evidence central roles of intestinal miRNAs as regulators of gene expression, influencing intestinal homeostasis and adaptation to environment in different strains and production phases., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Calcium (Ca) and phosphorus (P) are essential nutrients that are linked to a large array of biological processes. Disturbances in Ca and P homeostasis in chickens are associated with a decline in growth and egg laying performance and environmental burden due to excessive P excretion rates. Improved utilization of minerals in particular of P sources contributes to healthy growth while preserving the finite resource of mineral P and mitigating environmental pollution. In the current study, high performance Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens at peak laying performance were examined to approximate the consequences of variable dietary Ca and P supply. The experimental design comprised four dietary groups with standard or reduced levels of either Ca or P or both (n = 10 birds per treatment group and strain) in order to stimulate intrinsic mechanisms to maintain homeostasis. Jejunal transcriptome profiles and the systemic endocrine regulation of mineral homeostasis were assessed (n = 80)., Results: Endogenous mechanisms to maintain mineral homeostasis in response to variations in the supply of Ca and P were effective in both laying hen strains. However, the LSL and LB appeared to adopt different molecular pathways, as shown by circulating vitamin D levels and strain-specific transcriptome patterns. Responses in LSL indicated altered proliferation rates of intestinal cells as well as adaptive responses at the level of paracellular transport and immunocompetence. Endogenous mechanisms in LB appeared to involve a restructuring of the epithelium, which may allow adaptation of absorption capacity via improved micro-anatomical characteristics., Conclusions: The results suggest that LSL and LB hens may exhibit different Ca, P, and vitamin D requirements, which have so far been neglected in the supply recommendations. There is a demand for trial data showing the mechanisms of endogenous factors of Ca and P homeostasis, such as vitamin D, at local and systemic levels in laying hens.

Phosphorus (P) and calcium (Ca) are critical for egg production in laying hens. Most of P in plant-based poultry diet is bound as phytic acid and needs to be hydrolysed before absorption. To increase P bioavailability, exogenous phytases or bioavailable rock phosphate is added in feed. There is growing evidence of the importance of miRNAs as the epicentre of intestinal homeostasis and functional properties. Therefore, we demonstrated the expression of miRNA profiles and the corresponding target genes due to the different levels of P (recommended vs. 20% reduction) and/or Ca (recommended vs. 15% reduction) in feed. Jejunal miRNA profiles of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) laying hens strains were used (n = 80). A total of 34 and 76 miRNAs were differentially expressed (DE) in the different diet groups within LSL and LB strains respectively. In LSL, the DE miRNAs and their targets were involved in calcium signaling pathway, inositol phosphate metabolism, and mitochondrial dysfunction. Similarly, in LB miRNAs targets were enriched in metabolic pathways such as glutathione metabolism, phosphonate metabolism and vitamin B6 metabolism. Our results suggest that both strains employ different intrinsic strategies to cope with modulated P and Ca supply and maintain mineral homeostasis.

Broiler eggs were either incubated at 37.8°C during the whole incubation period (control), or at higher (38.8°C, group H) and lower temperatures (36.8°C, group L) from embryonic day (ED) 7 up to ED 10 (ED 7 to 10) or from ED 10 up to ED 13 (ED 10 to 13). Before and after this temperature treatment the eggs were incubated at 37.8°C. The day-old chicks were weighted, sexed and fed up to day 35. On days 1 and 35 samples were taken from the breast and leg muscles for analyzing of the mitochondrial respiratory activity (MRA) and from the breast muscles for analysis of the cross-sectional areas (CSA) and the glycogen phosphorylase (GP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and cytochrome oxidase (COX) activities. Statistical analysis showed that treatment (control, group H, group L), sex and their interaction, but not the treatment period (ED 7 to 10; ED 10 to 13), significantly influenced the results. Group H chicks had lower (P⩽0.05) body and heart weights but higher (P⩽0.05) liver weights, CSA values, leg MRA as well as PFK, LDH, CS, GP and COX activities compared with the group L chicks. The results of the control chicks differ (P⩽0.05) from those of the group H (body, heart weight, COX), the group L chicks (liver weight, PFK, LDH, CS, GP) or the birds of both other groups (CSA). The group H broiler had higher (P⩽0.05) body and leg weights as well as LDH, CS, COX and GP activities than the group L broilers. The BWs and the LDH and GP results of the control broiler differ (P⩽0.05) from those of both other groups or from the results of the group H (CS) and group L broiler (COX). Female broilers had lower (P⩽0.05) body, breast and leg weights, but higher (P⩽0.05) CSA, LDH, CS and GP activities than the male animals. Analysis of treatment×sex interaction showed that group H hens had higher (P⩽0.05) body and breast weights, LDH and GP activities compared with the group L hens, whereas in the male broiler no effect of the interaction could be found, except for the lower (P⩽0.05) CSA values in the group H than group L cocks. The treatment effects are probably due to altered embryonic activity and related molecular mechanisms. The sex-related differences in the broiler indicate that these alterations already occur in the embryos and chicks, but become significant with the sexual dimorphism after hatch.

Currently, optimization of feed efficiency is one of the main challenges in improvement programs of livestock and poultry genetics. The objective of this review is to present the genetic aspects of feed efficiency related traits in meat-type chicken and possible ways to reduce the environmental impact of poultry meat production with effective breeding. Basic measures of feed efficiency are defined and the genetic background of these traits, including a review of heritabilities is described. Moreover, a number of genomic regions and candidate genes determining feed efficiency traits of broilers that were detected over the past decades are described. Classical and genomic selection strategies for feed efficiency in the context of its relationships with other performance traits are discussed as well. Finally, future strategies to improve feed digestibility are described as it is expected that they will decrease wastes and greenhouse gas emission. Further genetic improvement of feed efficiency, should be examined jointly with appropriate feeding strategies in broilers.

Phytogenic feed additives represent a potential alternative to antibiotics with attributed health and growth-promoting effects. Chickens supplemented with an essential oil blend, a Quillaja saponin blend, or a combination of both phytogenic preparations showed a comprehensively and significantly improved apparent ileal digestibility of crude protein and amino acids compared to control birds. Accordingly, holistic transcriptomic analyses of jejunum and liver samples indicated alterations of macromolecule transporters and processing pathways likely culminating in an increased uptake and metabolizing of carbohydrates and fatty acids. Complementary analyses in Caco-2 showed a significant increase in transporter recruitment to the membrane (SGLT1 and PEPT1) after addition of essential oils and saponins. Although the penetrance of effects differed for the used phytogenic feed additives, the results indicate for an overlapping mode of action including local effects at the intestinal border and systemic alterations of macronutrient metabolism resulting in an improved performance of broilers.

1. The objective of this study was to indicate the most informative chromosomal regions and candidate genes connected to body weight at 36 d, body weight at 39 d, body weight changes between 39 and 46 d, feed intake between 39 and 46 d and feed conversion ratio of meat-type chicken based on genomic data using entropy analysis. 2. Data contained information about 862 genotyped individuals from a Cobb commercial line using 60K Illumina iSelect chicken array and information from 42 770 Single Nucleotide Polymorphisms (SNPs). Entropy analysis was employed to detect important chromosomal regions determining the target traits. Locations of genes within the designated regions on each chromosome and for each trait were verified using the Ensembl genome database. 3. The most informative SNPs were located on chromosomes 1, 2, 4, 8, 12 and Z, whereas clusters of the most informative pairs of SNPs connected to all recorded traits were located on chromosomes 1, 2, 3, 4, 6, 12, 20 and Z. The identified chromosomal localisations overlap with genes functionally connected to the nervous system and gastrointestinal tract.

Background: In oviparous species accidental variation of incubation temperatures may occur under natural conditions and mechanisms may have evolved by natural selection that facilitate coping with these stressors. However, under controlled artificial incubation modification of egg incubation temperature has been shown to have a wide-ranging impact on post-hatch development in several poultry species. Because developmental changes initiated in-ovo can affect poultry production, understanding the molecular routes and epigenetic alterations induced by incubation temperature differences may allow targeted modification of phenotypes., Results: In order to identify molecular pathways responsive to variable incubation temperature, broiler eggs were incubated at a lower or higher temperature (36.8 °C, 38.8 °C) relative to control (37.8 °C) over two developmental intervals, embryonic days (E) 7-10 and 10-13. Global gene expression of M. gastrocnemius was assayed at E10, E13, and slaughter age [post-hatch day (D) 35] (6 groups; 3 time points; 8 animals each) by microarray analysis and treated samples were compared to controls within each time point. Transcript abundance differed for between 113 and 738 genes, depending on treatment group, compared to the respective control. In particular, higher incubation temperature during E7-10 immediately affected pathways involved in energy and lipid metabolism, cell signaling, and muscle development more so than did other conditions. But lower incubation temperature during E10-13 affected pathways related to cellular function and growth, and development of organ, tissue, and muscle as well as nutrient metabolism pathways at D35., Conclusion: Shifts in incubation temperature provoke specific immediate and long-term transcriptional responses. Further, the transcriptional response to lower incubation temperature, which did not affect the phenotypes, mediates compensatory effects reflecting adaptability. In contrast, higher incubation temperature triggers gene expression and has long-term effects on the phenotype, reflecting considerable phenotypic plasticity.

Individual feed conversion efficiency (FCE) is a major trait that influences the usage of energy resources and the ecological footprint of livestock production. The underlying biological processes of FCE are complex and are influenced by factors as diverse as climate, feed properties, gut microbiota, and individual genetic predisposition. To gain an insight to the genetic relationships with FCE traits and to contribute to the improvement of FCE in commercial chicken lines, a genome-wide association study was conducted using a commercial broiler population (n = 859) tested for FCE and weight traits during the finisher period from 39 to 46 days of age. Both single-marker (generalized linear model) and multi-marker (Bayesian approach) analyses were applied to the dataset to detect genes associated with the variability in FCE. The separate analyses revealed 22 quantitative trait loci (QTL) regions on 13 different chromosomes; the integration of both approaches resulted in 7 overlapping QTL regions. The analyses pointed to acylglycerol kinase (AGK) and general transcription factor 2-I (GTF2I) as positional and functional candidate genes. Non-synonymous polymorphisms of both candidate genes revealed evidence for a functional importance of these genes by influencing different biological aspects of FCE.

In a project on the biodiversity of chickens funded by the European Commission (EC), eight laboratories collaborated to assess the genetic variation within and between 52 populations from a wide range of chicken types. Twenty-two di-nucleotide microsatellite markers were used to genotype DNA pools of 50 birds from each population. The polymorphism measures for the average, the least polymorphic population (inbred C line) and the most polymorphic population (Gallus gallus spadiceus) were, respectively, as follows: number of alleles per locus, per population: 3.5, 1.3 and 5.2; average gene diversity across markers: 0.47, 0.05 and 0.64; and proportion of polymorphic markers: 0.91, 0.25 and 1.0. These were in good agreement with the breeding history of the populations. For instance, unselected populations were found to be more polymorphic than selected breeds such as layers. Thus DNA pools are effective in the preliminary assessment of genetic variation of populations and markers. Mean genetic distance indicates the extent to which a given population shares its genetic diversity with that of the whole tested gene pool and is a useful criterion for conservation of diversity. The distribution of population-specific (private) alleles and the amount of genetic variation shared among populations supports the hypothesis that the red jungle fowl is the main progenitor of the domesticated chicken.

We tested the utility of genetic cluster analysis in ascertaining population structure of a large data set for which population structure was previously known. Each of 600 individuals representing 20 distinct chicken breeds was genotyped for 27 microsatellite loci, and individual multilocus genotypes were used to infer genetic clusters. Individuals from each breed were inferred to belong mostly to the same cluster. The clustering success rate, measuring the fraction of individuals that were properly inferred to belong to their correct breeds, was consistently approximately 98%. When markers of highest expected heterozygosity were used, genotypes that included at least 8-10 highly variable markers from among the 27 markers genotyped also achieved >95% clustering success. When 12-15 highly variable markers and only 15-20 of the 30 individuals per breed were used, clustering success was at least 90%. We suggest that in species for which population structure is of interest, databases of multilocus genotypes at highly variable markers should be compiled. These genotypes could then be used as training samples for genetic cluster analysis and to facilitate assignments of individuals of unknown origin to populations. The clustering algorithm has potential applications in defining the within-species genetic units that are useful in problems of conservation.

The genetic variability of various local chicken populations derived from Bolivia, India, Nigeria and Tanzania was evaluated with 22 microsatellites. Between two and 11 alleles per locus were detected. All populations showed high levels of heterozygosity with the lowest value of 45% for the population named Aseel from India and the highest value of 67% for Arusha from Tanzania. A dendrogram was constructed based on CHORD distance by upgMa analysis. Within this tree the populations were assorted according to their geographical origin. Bootstrapping values within the dendrogram were between 37 and 99%. The contribution of the determination of genetic variability with genetic markers to the decision on conservation and/or further use of the populations in crossbreeding programs designed to create genetic stocks with improved adaptability and productivity in tropical countries is discussed.

1. DNA fingerprints of chickens from 2 commercial lines were used to identify oligonucleotide probes providing informative DNA fingerprints. 2. The oligonucleotides [CA]8, [CAC]5, [GGAT]4 and [GACA]4, producing a high number of bands of sufficient intensity and regular distribution, were chosen for further analysis out of 10 tested. 3. Analyses of banding patterns within families revealed Mendelian inheritance of the fragments detected. The DNA fingerprints obtained with the 4 chosen oligonucleotide probes showed about 40 scorable bands in total. 4. Comparison of banding patterns within and between the chicken lines for all 4 oligonucleotide probes revealed levels of bandsharing which did not differ significantly. The number of loci detected by these probes ranged from 25 to 30 each. 5. The probes [CA]8, [CAC]5, [GGAT]4 and [GACA]4 can be used to produce informative DNA fingerprints of chicken. These probes provide estimates of the genetic similarity/variability of individuals or of populations and provide a valid measure of the actual degree of genetic similarity/variability.

A DNA fingerprinting technique was used to assess the extent of genetic variation within and between 12 lines of chickens of different origin. DNA fingerprints were obtained with the restriction endonucleases AluI and HinfI and with the oligonucleotide probes (CA)8, (CAC)5, (GGAT)4, and (GACA)4. Different methods that are based on band sharing and band frequency were tested to estimate genetic variation within and between populations. The genetic variability was significantly different within the populations. It was highest in a commercial broiler line and lowest in a White Leghorn inbred line. All three measures of genetic variation within populations provided results that were highly correlated (r = 0.89-0.97). A lower degree of correspondence was observed for the estimation of genetic variation between populations by three different methods. This is shown by differences of the phylogenetic trees and by coefficients of correlation between these measures ranging from r = 0.51-0.96.

Presents a study on the estimation of genetic variation based on deoxyribosenucleic acid (DNA) fingerprinting and microsatellites in samples of chicken lines. Details on the breeds; Detection of microsatellites; Measures of genetic variation; Description of genetic distance between populations.