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Browsing by Author "Rothschild, Max F."

Now showing 1 - 9 of 9
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    Genetic analysis of production, physiological, and egg quality traits in heat-challenged commercial white egg-laying hens using 600k SNP array data
    Rowland, Kaylee; Ashwell, Christopher M.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (2019-06-25)
    Background Heat stress negatively affects the welfare and production of chickens. High ambient temperature is considered one of the most ubiquitous abiotic environmental challenges to laying hens around the world. In this study, we recorded several production traits, feed intake, body weight, digestibility, and egg quality of 400 commercial white egg-laying hens before and during a 4-week heat treatment. For the phenotypes that had estimated heritabilities (using 600k SNP chip data) higher than 0, SNP associations were tested using the same 600k genotype data. Results Seventeen phenotypes had heritability estimates higher than 0, including measurements at various time points for feed intake, feed efficiency, body weight, albumen weight, egg quality expressed in Haugh units, egg mass, and also for change in egg mass from prior to heat exposure to various time points during the 4-week heat treatment. Quantitative trait loci (QTL) were identified for 10 of these 17 phenotypes. Some of the phenotypes shared QTL including Haugh units before heat exposure and after 4 weeks of heat treatment. Conclusions Estimated heritabilities differed from 0 for 17 traits, which indicates that they are under genetic control and that there is potential for improving these traits through selective breeding. The association of different QTL with the same phenotypes before heat exposure and during heat treatment indicates that genomic control of traits under heat stress is distinct from that under thermoneutral conditions. This study contributes to the knowledge on the genomic control of response to heat stress in laying hens.
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    Genetic lines respond uniquely within the chicken thymic transcriptome to acute heat stress and low dose lipopolysaccharide
    Monson, Melissa S.; Van Goor, Angelica G.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (Springer Nature, 2019-09-20)
    Exposure to high temperatures is known to impair immune functions and disease resistance of poultry. Characterizing changes in the transcriptome can help identify mechanisms by which immune tissues, such as the thymus, respond to heat stress. In this study, 22-day-old chickens from two genetic lines (a relatively resistant Fayoumi line and a more susceptible broiler line) were exposed to acute heat stress (35 degrees C) and/or immune simulation with lipopolysaccharide (LPS; 100 mu g/kg). Transcriptome responses in the thymus were identified by RNA-sequencing (RNA-seq). Expression of most genes was unaffected by heat and/or LPS in the Fayoumi line, whereas these treatments had more impact in the broiler line. Comparisons between the broiler and Fayoumi transcriptomes identified a large number of significant genes both at homeostasis and in response to treatment. Functional analyses predicted that gene expression changes impact immune responses, apoptosis, cell activation, migration, and adhesion. In broilers, acute heat stress changed thymic expression responses to LPS and could impact thymocyte survival and trafficking, and thereby contribute to the negative effects of high temperatures on immune responses. Identification of these genes and pathways provides a foundation for testing targets to improve disease resistance in heat-stressed chickens.
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    Genomic Comparison of Indigenous African and Northern European Chickens Reveals Putative Mechanisms of Stress Tolerance Related to Environmental Selection Pressure
    Fleming, Damarius S.; Weigend, Steffen; Simianer, Henner; Weigend, Annett; Rothschild, Max F.; Schmidt, Carl J.; Ashwell, Christopher M.; Persia, Michael E.; Reecy, James; Lamont, Susan J. (Genetics Society of America, 2017-05)
    Global climate change is increasing the magnitude of environmental stressors, such as temperature, pathogens, and drought, that limit the survivability and sustainability of livestock production. Poultry production and its expansion is dependent upon robust animals that are able to cope with stressors in multiple environments. Understanding the genetic strategies that indigenous, noncommercial breeds have evolved to survive in their environment could help to elucidate molecular mechanisms underlying biological traits of environmental adaptation. We examined poultry from diverse breeds and climates of Africa and Northern Europe for selection signatures that have allowed them to adapt to their indigenous environments. Selection signatures were studied using a combination of population genomic methods that employed FST, integrated haplotype score (iHS), and runs of homozygosity (ROH) procedures. All the analyses indicated differences in environment as a driver of selective pressure in both groups of populations. The analyses revealed unique differences in the genomic regions under selection pressure from the environment for each population. The African chickens showed stronger selection toward stress signaling and angiogenesis, while the Northern European chickens showed more selection pressure toward processes related to energy homeostasis. The results suggest that chromosomes 2 and 27 are the most diverged between populations and the most selected upon within the African (chromosome 27) and Northern European (chromosome 2) birds. Examination of the divergent populations has provided new insight into genes under possible selection related to tolerance of a population's indigenous environment that may be baselines for examining the genomic contribution to tolerance adaptions.
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    Identification of quantitative trait loci for body temperature, body weight, breast yield, and digestibility in an advanced intercross line of chickens under heat stress
    Van Goor, Angelica G.; Bolek, Kevin J.; Ashwell, Christopher M.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (2015-12-17)
    Background Losses in poultry production due to heat stress have considerable negative economic consequences. Previous studies in poultry have elucidated a genetic influence on response to heat. Using a unique chicken genetic resource, we identified genomic regions associated with body temperature (BT), body weight (BW), breast yield, and digestibility measured during heat stress. Identifying genes associated with a favorable response during high ambient temperature can facilitate genetic selection of heat-resilient chickens. Methods Generations F18 and F19 of a broiler (heat-susceptible) × Fayoumi (heat-resistant) advanced intercross line (AIL) were used to fine-map quantitative trait loci (QTL). Six hundred and thirty-one birds were exposed to daily heat cycles from 22 to 28 days of age, and phenotypes were measured before heat treatment, on the 1st day and after 1 week of heat treatment. BT was measured at these three phases and BW at pre-heat treatment and after 1 week of heat treatment. Breast muscle yield was calculated as the percentage of BW at day 28. Ileal feed digestibility was assayed from digesta collected from the ileum at day 28. Four hundred and sixty-eight AIL were genotyped using the 600 K Affymetrix chicken SNP (single nucleotide polymorphism) array. Trait heritabilities were estimated using an animal model. A genome-wide association study (GWAS) for these traits and changes in BT and BW was conducted using Bayesian analyses. Candidate genes were identified within 200-kb regions around SNPs with significant association signals. Results Heritabilities were low to moderate (0.03 to 0.35). We identified QTL for BT on Gallus gallus chromosome (GGA)14, 15, 26, and 27; BW on GGA1 to 8, 10, 14, and 21; dry matter digestibility on GGA19, 20 and 21; and QTL of very large effect for breast muscle yield on GGA1, 15, and 22 with a single 1-Mb window on GGA1 explaining more than 15 % of the genetic variation. Conclusions This is the first study to estimate heritabilities and perform GWAS using this AIL for traits measured during heat stress. Significant QTL as well as low to moderate heritabilities were found for each trait, and these QTL may facilitate selection for improved animal performance in hot climatic conditions.
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    Immunomodulatory effects of heat stress and lipopolysaccharide on the bursal transcriptome in two distinct chicken lines
    Monson, Melissa S.; Van Goor, Angelica G.; Ashwell, Christopher M.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (2018-08-30)
    Background Exposure to heat stress suppresses poultry immune responses, which can increase susceptibility to infectious diseases and, thereby, intensify the negative effects of heat on poultry welfare and performance. Identifying genes and pathways that are affected by high temperatures, especially heat-induced changes in immune responses, could provide targets to improve disease resistance in chickens. This study utilized RNA-sequencing (RNA-seq) to investigate transcriptome responses in the bursa of Fabricius, a primary immune tissue, after exposure to acute heat stress and/or subcutaneous immune stimulation with lipopolysaccharide (LPS) in a 2 × 2 factorial design: Thermoneutral + Saline, Heat + Saline, Thermoneutral + LPS and Heat + LPS. All treatments were investigated in two chicken lines: a relatively heat- and disease-resistant Fayoumi line and a more susceptible broiler line. Results Differential expression analysis determined that Heat + Saline had limited impact on gene expression (N = 1 or 63 genes) in broiler or Fayoumi bursa. However, Thermoneutral + LPS and Heat + LPS generated many expression changes in Fayoumi bursa (N = 368 and 804 genes). Thermoneutral + LPS was predicted to increase immune-related cell signaling and cell migration, while Heat + LPS would activate mortality-related functions and decrease expression in WNT signaling pathways. Further inter-treatment comparisons in the Fayoumi line revealed that heat stress prevented many of the expression changes caused by LPS. Although fewer significant expression changes were observed in the broiler bursa after exposure to Thermoneutral + LPS (N = 59 genes) or to Heat + LPS (N = 146 genes), both treatments were predicted to increase cell migration. Direct comparison between lines (broiler to Fayoumi) confirmed that each line had distinct responses to treatment. Conclusions Transcriptome analysis identified genes and pathways involved in bursal responses to heat stress and LPS and elucidated that these effects were greatest in the combined treatment. The interaction between heat and LPS was line dependent, with suppressive expression changes primarily in the Fayoumi line. Potential target genes, especially those involved in cell migration and immune signaling, can inform future research on heat stress in poultry and could prove useful for improving disease resistance.
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    Quantitative trait loci identified for blood chemistry components of an advanced intercross line of chickens under heat stress
    Van Goor, Angelica G.; Ashwell, Christopher M.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (2016-04-14)
    Background Heat stress in poultry results in considerable economic losses and is a concern for both animal health and welfare. Physiological changes occur during periods of heat stress, including changes in blood chemistry components. A highly advanced intercross line, created from a broiler (heat susceptible) by Fayoumi (heat resistant) cross, was exposed to daily heat cycles for seven days starting at 22 days of age. Blood components measured pre-heat treatment and on the seventh day of heat treatment included pH, pCO2, pO2, base excess, HCO3, TCO2, K, Na, ionized Ca, hematocrit, hemoglobin, sO2, and glucose. A genome-wide association study (GWAS) for these traits and their calculated changes was conducted to identify quantitative trait loci (QTL) using a 600 K SNP panel. Results There were significant increases in pH, base excess, HCO3, TCO2, ionized Ca, hematocrit, hemoglobin, and sO2, and significant decreases in pCO2 and glucose after 7 days of heat treatment. Heritabilities ranged from 0.01-0.21 for pre-heat measurements, 0.01-0.23 for measurements taken during heat, and 0.00-0.10 for the calculated change due to heat treatment. All blood components were highly correlated within measurement days, but not correlated between measurement days. The GWAS revealed 61 QTL for all traits, located on GGA (Gallus gallus chromosome) 1, 3, 6, 9, 10, 12–14, 17, 18, 21–28, and Z. A functional analysis of the genes in these QTL regions identified the Angiopoietin pathway as significant. The QTL that co-localized for three or more traits were on GGA10, 22, 26, 28, and Z and revealed candidate genes for birds’ response to heat stress. Conclusions The results of this study contribute to our knowledge of levels and heritabilities of several blood components of chickens under thermoneutral and heat stress conditions. Most components responded to heat treatment. Mapped QTL may serve as markers for genomic selection to enhance heat tolerance in poultry. The Angiopoietin pathway is likely involved in the response to heat stress in chickens. Several candidate genes were identified, giving additional insight into potential mechanisms of physiologic response to high ambient temperatures.
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    Transcriptome Response of Liver and Muscle in Heat-Stressed Laying Hens
    Wang, Yan; Jia, Xinzheng; Hsieh, John C. F.; Monson, Melissa S.; Zhang, Jibin; Shu, Dingming; Nie, Qinghua; Persia, Michael E.; Rothschild, Max F.; Lamont, Susan J. (MDPI, 2021-02-10)
    Exposure to high ambient temperature has detrimental effects on poultry welfare and production. Although changes in gene expression due to heat exposure have been well described for broiler chickens, knowledge of the effects of heat on laying hens is still relatively limited. In this study, we profiled the transcriptome for pectoralis major muscle (n = 24) and liver (n = 24), during a 4-week cyclic heating experiment performed on layers in the early phase of egg production. Both heat-control and time-based contrasts were analyzed to determine differentially expressed genes (DEGs). Heat exposure induced different changes in gene expression for the two tissues, and we also observed changes in gene expression over time in the control animals suggesting that metabolic changes occurred during the transition from onset of lay to peak egg production. A total of 73 DEGs in liver were shared between the 3 h heat-control contrast, and the 4-week versus 3 h time contrast in the control group, suggesting a core set of genes that is responsible for maintenance of metabolic homeostasis regardless of the physiologic stressor (heat or commencing egg production). The identified DEGs improve our understanding of the layer’s response to stressors and may serve as targets for genetic selection in the future to improve resilience.
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    Unique genetic responses revealed in RNA-seq of the spleen of chickens stimulated with lipopolysaccharide and short-term heat
    Van Goor, Angelica G.; Ashwell, Christopher M.; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (PLOS, 2017-02-06)
    Climate change and disease have large negative impacts on poultry production, but little is known about the interactions of responses to these stressors in chickens. Fayoumi (heat and disease resistant) and broiler (heat and disease susceptible) chicken lines were stimulated at 22 days of age, using a 2x2x2 factorial design including: breed (Fayoumi or broiler), inflammatory stimulus (lipopolysaccharide (LPS) or saline), and temperature (35°C or 25°C). Transcriptional changes in spleens were analyzed using RNA-sequencing on the Illumina HiSeq 2500. Thirty-two individual cDNA libraries were sequenced (four per treatment) and an average of 22 million reads were generated per library. Stimulation with LPS induced more differentially expressed genes (DEG, log2 fold change ≥ 2 and FDR ≤ 0.05) in the broiler (N = 283) than the Fayoumi (N = 85), whereas heat treatment resulted in fewer DEG in broiler (N = 22) compared to Fayoumi (N = 107). The double stimulus of LPS+heat induced the largest numbers of changes in gene expression, for which broiler had 567 DEG and Fayoumi had 1471 DEG of which 399 were shared between breeds. Further analysis of DEG revealed pathways impacted by these stressors such as Remodelling of Epithelial Adherens Junctions due to heat stress, Granulocyte Adhesion and Diapedesis due to LPS, and Hepatic Fibrosis/Hepatic Stellate Cell Activation due to LPS+heat. The genes and pathways identified provide deeper understanding of the response to the applied stressors and may serve as biomarkers for genetic selection for heat and disease tolerant chickens.
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    Venous blood gas and chemistry components are moderately heritable in commercial white egg-laying hens under acute or chronic heat exposure
    Rowland, Kaylee; Persia, Michael E.; Rothschild, Max F.; Schmidt, Carl J.; Lamont, Susan J. (Oxford University Press, 2019-09-01)
    Heat stress has a large negative impact on poultry around the world in both intensive and small-scale production systems. Better understanding of genetic factors contributing to response to high ambient temperatures would provide a basis to develop strategies for alleviating negative impacts of heat on poultry production. The objective of this work was to characterize the genetic control (heritability estimate and quantitative trait loci (QTL)) of blood chemistry components before and after exposure to acute and chronic high ambient temperature in a commercial egg laying line Hy-Line W-36 female parent line mature hens were exposed to 4 wk of daily cyclic heat exposure. Blood was collected pre-heat, on the first day of heat, and 2 and 4 wk post heat initiation and analyzed immediately using an i-STAT® hand-held blood analyzer. Thirteen blood components were quantified at the 4 time points: pH, pCO2, pO2, HCO3, TCO2, sO2, iCa, Na, K, base excess, glucose, “hematocrit” (estimated from blood electrical conductivity, BEC), and “hemoglobin” (calculated from BEC). Heritabilities were estimated using genomic relationship information obtained from 600k SNP chip data. All 13 parameters exhibited a significant change after 5 h of heat exposure and most did not return to pre-heat levels throughout the duration of the study. Eight parameters (base excess, glucose, hemoglobin, HCO3, hematocrit, K, pCO2, TCO2) had heritability estimates differing from zero at one or more time points (0.21 to 0.45). The traits with significant heritability would be good candidates for use as biomarkers in a selection program if they are correlated with traits of economic importance that are more difficult to measure. QTL were identified for nine of the traits at one or more time point. These nine traits, however, did not have significant heritability estimates suggesting that while some QTL have been identified their effects are generally small.