Korat chicken (KRC), a slow-growing chicken known for its unique meat flavor and nutritional value, exhibits variation in feed efficiency (FE). Since the hypothalamus acts as a convergent and integrative center for multiple nutrient-related signals, this study aims to compare transcriptomic profiles and neuronal pathways in hypothalamus between two groups of male KRCs differing in residual feed intake (RFI). RNA was extracted from hypothalamic tissues of males KRC either in the low-RFI (n=10) or in the high-RFI (n=10) group. The results showed 257 DEGs, including 138 upregulated and 119 downregulated genes in the low RFI compared to the high-RFI groups. Gene Ontology analysis of the DEGs revealed that they were mainly related to metabolic processes and transporter activity. Kyoto Encyclopedia of Genes and Genomes pathway analysis identified 3 significant pathways, including the folate biosynthesis (3 genes including GCH1, TPH2, and TH), tyrosine metabolism (3 genes including DDC, TH and FAH), and tryptophan metabolism (3 genes including DDC, TPH2, and TDO2) pathways. The upregulated genes in the low-RFI group (TPH2, DDC, and TH) were enriched in the folate biosynthesis, tyrosine metabolism, and tryptophan metabolism pathways, which is consistent with the observed plasma concentrations of dopamine (DA) and serotonin/5-hydroxytryptamine (ST/5-HT). These findings suggest that differences in DA and ST/5-HT levels among the chicken groups may be associated with variation in FE. Furthermore, genes such as GCH1, TPH2, DDC, TH, and FAH could be candidate genes supporting the role of hypothalamus in regulating FE of slow-growing KRC.

This study investigated the effects of curcumin (CUR)- and capsaicin (CAP)- loaded nanoemulsion on blood biochemical changes, oxidative status, jejunal morphology, inflammatory parameters, and performance of slow-growing Korat chickens (KRC) raised under high stocking density (HSD). A total of 480 male KRC (21 d of age) were allocated into four groups: (1) HSD without supplementation, (2) normal stocking density (NSD) without supplementation, (3) HSD supplemented with CUR and CAP in powdered form (P-CUR+CAP), and (4) HSD supplemented with CUR- and CAP-loaded nanoemulsions (NE-CUR+CAP). Chickens receiving NE-CUR+CAP showed no adverse changes in liver or kidney function compared with other groups. The heterophil-to-lymphocyte ratio was reduced in NE-CUR+CAP group relative to HSD group and was comparable with NSD and P-CUR+CAP groups (P < 0.05). NE-CUR+CAP also lowered levels of TBA in the liver and jejunum while enhancing hepatic superoxide dismutase activity compared with HSD group (P < 0.05). Villus height, villus height-to-crypt depth ratio, anti-inflammatory response, and cecal Lactobacillus counts were improved, whereas crypt depth and cecal Escherichia coli were reduced in the NE-CUR+CAP group (P < 0.05). Although feed intake, BW, and body weight gain were not affected, the feed conversion ratio was significantly lower in NE-CUR+CAP compared with HSD group (P < 0.05). In conclusion, NE-CUR+CAP mitigated oxidative stress and inflammation, improved intestinal health, and enhanced feed efficiency in slow-growing chickens raised under HSD.

Gene expression profiles and the heterogeneity among hormone-producing pituitary cells remain poorly characterized in most vertebrates, especially in chicken embryos. Using single-cell RNA sequencing, the transcriptomes of 4346 basal and 10 835 corticosterone (CORT)-treated embryonic day 11 chicken pituitary cells were sequenced. Classical endocrine cell clusters were identified, and some were shown to express previously unreported marker genes. A cluster of uncommitted cells was identified that expressed markers for multiple endocrine cell types, with ∼30% coexpressing Gh and Pomc mRNA. We named this population of cells the cortico-somatotrophs. The existence of cortico-somatotrophs were confirmed at both the mRNA and protein level. We further characterized the corticosomatotrophs by utilizing the known effect of CORT to increase somatotroph abundance. Identification of cortico-somatotrophs challenges the prevailing view that corticotrophs and somatotrophs develop from distinct cell lineages.

Numerous studies have implicated glucocorticoids in the regulation of somatotroph differentiation. However, few studies have investigated a requirement for glucocorticoid receptors (GR) in this process. We hypothesized that GR is essential for the normal ontogeny of pituitary growth hormone (GH) during mouse embryonic development. Anterior pituitary cells were isolated from e12.5 to e13.5 mice and e11 chickens and cultured with or without corticosterone (CORT) in the absence or presence of ZK98299, a GR-specific antagonist. CORT induced GH mRNA expression in pituitary cells from both species, and this response was blocked by inclusion of the GR antagonist. Mouse embryos with pituitary-targeted knockout of GR were generated utilizing the cre-LoxP Recombinase system under control of the pituitary-specific alpha-glycoprotein subunit (αGSU) promoter. All cre-positive GR(-/-) embryos died at birth. Therefore, anterior pituitary, brain, heart, liver, and muscle tissues, were collected on embryonic days 17.5/18.5 for RNA isolation and RT-qPCR analysis. Cre mRNA expression was only found in the pituitary, and GR mRNA levels were significantly decreased in the pituitaries of GR(-/-) embryos. GH mRNA was significantly decreased in pituitary-targeted GR(-/-) knockout embryos in comparison to wild-type GR(+/+) embryos. Significant differences in expression of other pituitary hormones in GR(-/-) embryos were not observed, indicating that the effect of pituitary-targeted knockout of GR was restricted to disruption of GH gene expression. To our knowledge, this is the first report that homozygous GR knockout in the anterior pituitary gland in mice suppresses embryonic GH expression, confirming an essential role for GR signaling in the normal ontogeny of somatotrophs.

Feed efficiency (FE) is a critical trait in poultry production, including slow-growing chicken breeds such as the Korat (KR) chicken. In this study, transcriptome profiling of the pituitary gland was performed to investigate the molecular mechanisms underlying FE differences between low residual feed intake (LRFI) and high residual feed intake (HRFI) groups. A total of 22 differentially expressed genes (DEGs) were identified, with three upregulated and 19 downregulated in the LRFI group. Among them, thyrotropin-releasing hormone receptor 3 (TRHR3), a gene associated with metabolic regulation in the pituitary, was significantly downregulated in the LRFI group, while elevated plasma levels of tetraiodothyronine (T4). Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis on gene sets revealed that better FE in KR chickens is related to linoleic and alpha-linolenic acid metabolism, as well as steroid hormone biosynthesis, highlighting their roles in thyroid hormone secretion, muscle development, and lipid metabolism. Unravelling pathways and key genes which are involved in variation of RFI in KR chickens will be useful to search for candidate DNA markers in the parental lines in order to improve FE of the KR chicken.

Selective breeding of broilers has significantly improved growth rates, muscle mass, and feed efficiency and may have influenced the neuroendocrine systems that regulate growth and metabolism. Embryonic development represents one-third of the life of a modern broiler. To assess the impact of genetic selection on the neuroendocrine regulation of growth and metabolism during embryonic development, we examined mRNA expression of growth-related genes in the hypothalamus and anterior pituitary of two chicken breeds: the modern Ross 708 broiler and the Athens Canadian Random Bred (ACRB) line, the oldest established strain for meat-type chickens. Hypothalami and pituitary glands were dissected from embryos at days 10, 12, 14, 16, and 18 of incubation (n = 4 for each combination of breed, age, and gender). Levels of mRNA for each target gene were quantified using reverse transcription-quantitative PCR. In the adrenocorticotropic axis, pituitary corticotropin-releasing hormone receptor 1 mRNA levels were influenced by the interaction of breed, age, and gender (P < 0.05). In the thyrotropic axis, pituitary thyroid-stimulating hormone β-subunit mRNA levels were affected by the interaction of breed, age, and gender (P < 0.05). In the somatotropic axis, mRNA levels of hypothalamic somatostatin were higher in ACRB than Ross, whereas overall pituitary growth hormone mRNA levels were greater in Ross than ACRB (P < 0.05). Pituitary growth hormone-releasing hormone receptor 2 and pituitary adenylate cyclase-activating polypeptide receptor 1 were influenced by the interaction between breed and age (P < 0.05). In the gonadotropic axis, hypothalamic gonadotropin-releasing hormone 1 and gonadotropin-inhibiting hormone were influenced by breed, age, and gender, while mRNA levels of pituitary follicle-stimulating hormone β-subunit were affected by the interaction between breed and age (P < 0.05). Hypothalamic agouti-related peptide, neuropeptide Y, and proopiomelanocortin mRNA levels were higher in ACRB than Ross in females (P < 0.05). These findings indicate that genetic selection of broilers has altered the adrenocorticotropic, somatotropic, thyrotropic, and gonadotropic axes, as well as hypothalamic control of appetite and metabolism during embryonic development.

Heat stress (HS) adversely impacts broiler health, productivity, and welfare, especially in market-age chickens. This study investigated the effects of early-life thermal conditioning (TC) on the expression of genes related to stress responses, thermoregulation, and metabolism in various tissues, including the hypothalamus, anterior pituitary gland, thyroid gland, adrenal gland, adipose tissue, liver, heart, breast, and thigh with and without HS in broilers. Male Ross 708 chicks were subjected to TC at 37.8°C or non-thermal conditioning (NTC) at 33°C for 24 h on d 3 after hatch. On d 31, birds from both groups were exposed to either HS (35°C) or non-heat stress (NHS; 22°C) conditions for 8 h, with collection of tissue samples for reverse transcription-quantitative PCR (RT-qPCR) analysis beginning after 4 h of HS. TC had no effect on production parameters, including BW, FI, BWG, and F/G. Key findings indicated that early-life TC significantly altered hypothalamic and pituitary expression of genes associated with stress adaptation under HS. Early-life TC increased hypothalamic neuropeptide Y expression under heat stress, which may contribute to improved stress adaptation. Additionally, TC resulted in higher heat shock protein 90 expression in thigh muscle and reduced heat shock protein 70 expression in breast muscle, highlighting tissue-specific adaptive responses. Interestingly, heart tissue from TC birds exhibited increased melanocortin 2 receptor mRNA levels under HS, suggesting improved cardiovascular resilience. Other tissues, including the adrenal gland, thyroid, liver, and adipose tissue, showed minimal gene expression changes in response to TC, implying selective tissue conditioning. These results suggest that early-life TC primes specific tissues to enhance HS resilience by modulating stress-response pathways, which may benefit poultry production in high-temperature environments. This research underscores the potential of TC as a management strategy for improving broiler response to HS challenges and circumventing the negative repercussions of HS on broiler health and performance.

The preovulatory hormonal surge (PS) consists of elevated circulating luteinizing hormone (LH) and progesterone levels and serves as the primary trigger for ovarian follicle ovulation. Increased LH and progesterone, produced by the pituitary and the granulosa layer of the largest ovarian follicle (F1), respectively, result from hypothalamic stimulation and steroid hormone feedback on the hypothalamo-pituitary-gonadal (HPG) axis. The hypothalamus, pituitary, F1 granulosa, and granulosa layer of the fifth largest follicle (F5) were isolated from converter turkey hens outside and during the PS and subjected to RNA sequencing (n = 6 per tissue). Differentially expressed genes were subjected to functional annotation using DAVID and IPA. A total of 12, 250, 1235, and 1938 DEGs were identified in the hypothalamus, pituitary, F1 granulosa, and F5 granulosa respectively (q<0.05, |fold change|>1.5, FPKM>1). Gene Ontology (GO) analysis revealed key roles for metabolic processes, steroid hormone feedback, and hypoxia induced gene expression changes. Upstream analysis identified a total of 4, 42, 126, and 393 potential regulators of downstream gene expression in the hypothalamus, pituitary, F1G, and F5G respectively, with a total of 63 potential regulators exhibiting differential expression between samples collected outside and during the PS (|z-score|>2). The results from this study serve to increase the current knowledge base surrounding the regulation of the PS in turkey hens. Through GO analysis, downstream processes and functions associated with the PS were linked to identified DEGs, and through upstream analysis, potential regulators of DEGs were identified for further analysis. Linking upstream regulators to the downstream PS and ovulation events could allow for genetic selection or manipulation of ovulation frequencies in turkey hens.

The somatotropic axis influences growth and metabolism, and many of its effects are a result of insulin-like growth factor (IGF) signaling modulated by IGF-binding proteins (IGFBPs). Modern commercial meat-type (broiler) chickens exhibit rapid and efficient growth and muscle accretion resulting from decades of commercial genetic selection, and it is not known how alterations in the IGF system has contributed to these improvements. To determine the effect of commercial genetic selection on somatotropic axis activity, two experiments were conducted comparing legacy Athens Canadian Random Bred and modern Ross 308 male broiler lines, one between embryonic days 10 and 18 and the second between post-hatch days 10 and 40. Gene expression was evaluated in liver and breast muscle (pectoralis major) and circulating hormone concentrations were measured post-hatch. During embryogenesis, no differences in IGF expression were found that corresponded with difference in body weight between the lines beginning on embryonic day 14. While hepatic IGF expression and circulating IGF did not differ between the lines post-hatch, expression of both IGF1 and IGF2 mRNA was greater in breast muscle of modern broilers. Differential expression of select IGFBPs suggests their action is dependent on developmental stage and site of production. Hepatic IGFBP1 appears to promote embryonic growth but inhibit post-hatch growth at select ages. Results suggest that local IGFBP4 may prevent breast muscle growth during embryogenesis but promote it after hatch. Post-hatch, IGFBP2 produced in liver appears to inhibit body growth, but IGFBP2 produced locally in breast muscle facilitates development of this tissue. The opposite appears true for IGFBP3, which seems to promote overall body growth when produced in liver and restrict breast muscle growth when produced locally. Results presented here suggest that paracrine IGF signaling in breast muscle may contribute to overall growth and muscle accretion in chickens, and that this activity is regulated in developmentally distinct and tissue-specific contexts through combinatorial action of IGFBPs.

Embryonic-to-neonatal development in chicken is characterized by high rates of lipid oxidation in the late-term embryonic liver and high rates of de novo lipogenesis in the neonatal liver. This rapid remodeling of hepatic mitochondrial and cytoplasmic networks occurs without symptoms of hepatocellular stress. Our objective was to characterize the metabolic phenotype of the embryonic and neonatal liver and explore whether these metabolic signatures are preserved in primary cultured hepatocytes. Plasma and liver metabolites were profiled using mass spectrometry based metabolomics on embryonic day 18 (ed18) and neonatal day 3 (nd3). Hepatocytes from ed18 and nd3 were isolated and cultured, and treated with insulin, glucagon, growth hormone and corticosterone to define hormonal responsiveness and determine their impacts on mitochondrial metabolism and lipogenesis. Metabolic profiling illustrated the clear transition from the embryonic liver relying on lipid oxidation to the neonatal liver upregulating de novo lipogenesis. This metabolic phenotype was conserved in the isolated hepatocytes from the embryos and the neonates. Cultured hepatocytes from the neonatal liver also maintained a robust response to insulin and glucagon, as evidenced by their contradictory effects on lipid oxidation and lipogenesis. In summary, primary hepatocytes from the embryonic and neonatal chicken could be a valuable tool to investigate mechanisms regulating hepatic mitochondrial metabolism and de novo lipogenesis.

I have served as Editor-in-Chief of World’s Poultry Science Journal since June 2021. My charge from the Board of Directors of the World’s Poultry Science Association when appointing me as Editor-in-Chief was to increase readership and make the journal even more relevant to poultry scientists and the poultry industries worldwide, while maintaining the journal as a publication outlet for scholarly works regardless of their origin of submission. Moving forward, I considered several approaches to achieve these goals. One approach is to attempt to improve the quality and relevance of articles published in the journal. This is certainly one of the responsibilities of the Editor-in-Chief. To that end, I am making efforts to improve the quality and rigour of peer-review for the journal. I require at least two reviews from recognised scientists in the field of the submission prior to making my decision. I am taking comments from reviewers related to manuscript quality, relevance, thoroughness, competence and timeliness quite seriously. My intention is that by improving these metrics for every article published, the overall quality and relevance of the journal will improve. In this issue, there are 14 articles, all of which underwent rigorous peer-review. As we strive to improve the metrics noted above, one might expect our rejection rate to increase, but that is not my intention. Rather, my intention by trying to raise the bar for publication in the journal is, quite simply, to improve the quality and relevance of the articles published. A second approach to improve the quality and relevance of the journal is to attract more submissions from regions of the globe with substantial engagement in poultry research and commercial poultry production. There are multiple venues for publication of articles related to poultry science and the poultry industries. Authors have a choice of journals to submit their manuscripts to for consideration for publication. Some of the factors taken into consideration by authors when selecting a journal to submit their work to include audience, prestige and cost. World’s Poultry Science Journal reaches a global audience, and there are no page charges to authors for publishing in the journal. Prestige of a journal is difficult to define, but one aspect is the relative ranking of the journal among other related journals in its category. Previously, I shared the good news that in 2021 World’s Poultry Science Journal was ranked 12 out of 63 journals in the Agriculture, Dairy and Animal Science category, with an impact factor of 2.915 (Porter 2021). As we improve the quality and relevance of the articles published in the journal, one would hope that citations would increase and the relative ranking and prestige of the journal would continue to improve. An increase in the prestige of the journal would likely attract more submissions from regions of the globe with substantial engagement in poultry research and commercial poultry production. A third approach to improve the quality and relevance of the journal is to solicit invited review articles from leading scientists on their specific area of research expertise. The current issue contains an invited review by Yuta Yoshida, Shotaro Nishimura, Shoji Tabata and Fuminori Kawabata titled ‘Chicken taste receptors and perception: recent WORLD’S POULTRY SCIENCE JOURNAL 2022, VOL. 78, NO. 1, 1–2 https://doi.org/10.1080/00439339.2022.2027614

I was named Editor-in-Chief of World’s Poultry Science Journal, beginning 1 June 2021. I would like to thank the Board of Directors of the World’s Poultry Science Association for their confidence i...

Low and high egg producing hens exhibit gene expression differences related to ovarian steroidogenesis. High egg producing hens display increased expression of genes involved in progesterone and estradiol production, in the granulosa layer of the largest follicle (F1G) and small white follicles (SWF), respectively, whereas low egg producing hens display increased expression of genes related to progesterone and androgen production in the granulosa (F5G) and theca interna layer (F5I) of the fifth largest follicle, respectively. Transcriptome analysis was performed on F1G, F5G, F5I, and SWF samples from low and high egg producing hens to identify novel regulators of ovarian steroidogenesis. In total, 12,221 differentially expressed genes (DEGs) were identified between low and high egg producing hens across the four cell types examined. Pathway analysis implied differential regulation of the hypothalamo-pituitary-thyroid (HPT) axis, particularly thyroid hormone transporters and thyroid hormone receptors, and of estradiol signaling in low and high egg producing hens. The HPT axis showed up-regulation in high egg producing hens in less mature follicles but up-regulation in low egg producing hens in more mature follicles. Estradiol signaling exclusively exhibited up-regulation in high egg producing hens. Treatment of SWF cells from low and high egg producing hens with thyroid hormone in vitro decreased estradiol production in cells from high egg producing hens to the levels seen in cells from low egg producing hens, whereas thyroid hormone treatment did not impact estradiol production in cells from low egg producing hens. Transcriptome analysis of the major cell types involved in steroidogenesis inferred the involvement of the HPT axis and estradiol signaling in the regulation of differential steroid hormone production seen among hens with different egg production levels.

Targeted in ovo green light (GL) photostimulation during the last days of broiler egg incubation increases embryonic expression of the somatotropic axis, similar to in ovo green light photostimulation from embryonic day (ED) 0 to the end of incubation. The aim of this study was to examine the effect of selected in ovo GL photostimulation periods on post-hatch broiler growth. Four hundred twenty fertile broiler eggs were divided into 7 treatment groups: the first incubated in the dark (standard conditions) as a negative control; the second incubated under monochromatic GL from ED0-ED20 (positive control); the third group incubated under monochromatic GL light from ED15-ED20; the fourth, fifth and sixth groups were incubated under monochromatic GL on ED16, ED17, and ED18, respectively; and the seventh group was incubated under monochromatic GL from ED18-ED20. All illumination was provided intermittently using LED lamps. After hatch, all chicks were transferred to a controlled room under standard rearing conditions. The group incubated under green light from ED18 until hatch showed similar results to the positive control group in body weights, as well as breast muscle weights (as % of body weights), and an elevation in the somatotropic axis activity during the experiment. We suggest that broiler embryos can be exposed to in ovo GL photostimulation from ED18 until hatch (hatching period), and still exhibit the same performance as obtained by photostimulation from d 0 of incubation.

A preovulatory surge (PS) of luteinizing hormone (LH) and progesterone triggers follicle ovulation, which is the first step of egg production and is orchestrated by the hypothalamo-pituitary-gonadal (HPG) axis. In the HPG axis, hypothalamic peptides, gonadotropin releasing hormone, and gonadotropin inhibitory hormone, control the production of follicle stimulating hormone and LH by the pituitary, which subsequently regulate ovarian production of estradiol and progesterone, respectively. The goal of this study was to characterize the HPG axis function of average egg producing hens by assessing plasma hormone profiles and hypothalamic, pituitary, and follicle gene expression outside and during the PS (n = 3 per group). Results were analyzed by a one-way ANOVA using the mixed models procedure of SAS. Plasma estradiol was not affected by the PS (P > 0.05), but plasma progesterone levels increased 8-fold during the PS when compared to basal progesterone levels (P < 0.05). HPG axis gene expression related to ovulation stimulation (e.g., GNRH, GNRHR, and LHB) was down-regulated during the PS; whereas gene expression related to follicle development (e.g., FSHB) was up-regulated during the PS. Additionally, in the hypothalamus and pituitary, estradiol receptor expression was up-regulated during the PS, whereas progesterone receptor expression was down-regulated during the PS. In the follicle cells, gene expression pertaining to progesterone (e.g., STAR), androgen (e.g., HSD17B1), and estradiol (e.g., CYP19A1) production was up-regulated during the PS. Prior to this study, the HPG axis had yet to be characterized during the PS in the turkey hen. This study showed that the PS significantly impacted gene expression in the hypothalamus, pituitary, and ovarian follicles. These results provide a foundation for further research into the regulation of ovulation and egg production in turkey hens.

Commercial selection for meat-type (broiler) chickens has produced economically valuable birds with fast growth rates, enhanced muscle mass, and highly efficient feed utilization. The physiological changes that account for this improvement and unintended consequences associated with them remain largely unexplored, despite their potential to guide further advancements in broiler production efficiency. To identify effects of genetic selection on hormonal signaling in the adrenocorticotropic and thyrotropic axes, gene expression in muscle and liver and post-hatch circulating hormone concentrations were measured in legacy [Athens Canadian Random Bred (ACRB)] and modern (Ross 308) male broilers between embryonic days (e) 10 and e18 and post-hatch days (d) 10 and d40. No interactive effects or main effects of line were observed for adrenocorticotropic gene expression during either developmental period, although age effects appeared for corticosteroid-binding globulin in liver during embryogenesis and post-hatch and glucocorticoid receptor in both tissues post-hatch. There was a main line effect for circulating corticosterone, with levels in ACRB greater than those in Ross. Several thyrotropic genes exhibited line-by-age interactions during embryonic or post-hatch development. In liver, embryonic expression of thyroid hormone receptor beta was greater in ACRB on e12, and deiodinase 3 (DIO3) levels were greater in Ross on e14 and e16. In juvenile liver, deiodinase 2 (DIO2) expression was greater in ACRB on d10 but greater in Ross on d20, while DIO3 was higher in ACRB on d30 and d40. Levels of thyroid hormone receptor alpha mRNA exhibited a main line effect, with levels greater in ACRB juvenile breast muscle. Several thyrotropic genes exhibited main age effects, including DIO2 and DIO3 in embryonic breast muscle, thyroid hormone receptor alpha and thyroid hormone receptor beta in post-hatch liver, and DIO2 in post-hatch breast muscle. Circulating triiodothyronine displayed a main line effect, with levels in Ross significantly reduced as compared to ACRB. These findings suggest that in modern broilers, a decrease in levels of hormones that control basal metabolism triiodothyronine and the stress response circulating corticosterone, as well as altered expression of genes regulating thyroid hormone activity, could contribute to lower heat production, reduced stress response, and altered nutrient partitioning, leading to more efficient feed utilization and faster, more productive growth.

Background The fasting-refeeding perturbation has been used extensively to reveal specific genes and metabolic pathways that control energy metabolism in the chicken. Most global transcriptional scans of the fasting-refeeding response in liver have focused on juvenile chickens that were 1, 2 or 4 weeks old. The present study was aimed at the immediate post-hatch period, in which newly-hatched chicks were subjected to fasting for 4, 24 or 48 h, then refed for 4, 24 or 48 h, and compared with a fully-fed control group at each age (D1-D4). Results Visual analysis of hepatic gene expression profiles using hierarchical and K-means clustering showed two distinct patterns, genes with higher expression during fasting and depressed expression upon refeeding and those with an opposing pattern of expression, which exhibit very low expression during fasting and more abundant expression with refeeding. Differentially-expressed genes (DEGs), identified from five prominent pair-wise contrasts of fed, fasted and refed conditions, were subjected to Ingenuity Pathway Analysis. This enabled mapping of analysis-ready (AR)-DEGs to canonical and metabolic pathways controlled by distinct gene interaction networks. The largest number of hepatic DEGs was identified by two contrasts: D2FED48h/D2FAST48h (968 genes) and D2FAST48h/D3REFED24h (1198 genes). The major genes acutely depressed by fasting and elevated upon refeeding included ANGTPL, ATPCL, DIO2, FASN, ME1, SCD, PPARG, SREBP2 and THRSPA— a primary lipogenic transcription factor. In contrast, major lipolytic genes were up-regulated by fasting or down-regulated after refeeding, including ALDOB, IL-15, LDHB, LPIN2, NFE2L2, NR3C1, NR0B1, PANK1, PPARA, SERTAD2 and UPP2 . Conclusions Transcriptional profiling of liver during fasting/re-feeding of newly-hatched chicks revealed several highly-expressed upstream regulators, which enable the metabolic switch from fasted ( lipolytic/gluconeogenic ) to fed or refed ( lipogenic/thermogenic ) states. This rapid homeorhetic shift of whole-body metabolism from a catabolic-fasting state to an anabolic-fed state appears precisely orchestrated by a small number of ligand-activated transcription factors that provide either a fasting-lipolytic state ( PPARA, NR3C1, NFE2L2, SERTAD2, FOX01, NR0B1, RXR) or a fully-fed and refed lipogenic/thermogenic state ( THRSPA, SREBF2, PPARG, PPARD, JUN, ATF3, CTNNB1 ). THRSPA has emerged as the key transcriptional regulator that drives lipogenesis and thermogenesis in hatchling chicks, as shown here in fed and re-fed states.

This study was conducted to evaluate potential hormonal mechanisms associated with the stress response, thermoregulation, and metabolic changes of broiler chickens exposed to high environmental temperature. Nine hundred 1-day-old male broiler chicks (Ross 708) were placed in floor pens and raised to 24 d. At 24 d, chicks were randomly assigned to 1 of 2 treatments, heat stress (HS) or no HS, and allocated into battery cages in 8 batteries (10 birds per cage, 2 cages per battery). On day 31, blood was collected prior to HS and analyzed using an iSTAT analyzer. Half of the batteries were then moved into 2 rooms with an elevated ambient temperature (35°C) for 8 h. The remaining batteries stayed in the thermoneutral rooms with an ambient temperature of 22°C. Beginning at 5 h after the initiation of HS, blood was collected and analyzed using an iSTAT analyzer, birds were euthanized, and hypothalamus and pituitary samples were collected (16 birds per treatment), flash frozen, and stored at −80°C until RNA extraction. Reverse transcription-quantitative PCR was used to compare mRNA levels of key corticotropic and thyrotrophic genes in the hypothalamus and pituitary. Levels of mRNA for each target gene were normalized to PGK1 (pituitary) and GAPDH (hypothalamus) mRNA. Differences were determined using mixed model ANOVA. HS decreased (P < 0.05) feed intake, BW, bicarbonate, potassium, CO2, and triiodothyronine, while it increased mortality, glucose, pH, plasma thyroxine, and corticosterone. Expression of pituitary corticotropin-releasing hormone receptor 1 was downregulated (P < 0.001), while corticotropin-releasing hormone receptor 2 mRNA levels were higher (P = 0.001) in HS birds. HS increased expression of thyroid hormone receptor β (P = 0.01) (2.8-fold) and thyroid stimulating hormone β (P = 0.009) (1.4-fold). HS did not affect levels of mRNA of genes evaluated in the hypothalamus. Results showed that HS significantly affected both the thyrotropic and corticotropic axes. Understanding the role and regulation of these pathways during HS will allow researchers to better evaluate management strategies to combat HS.

Background High egg producing hens ( HEPH ) show increased hypothalamic and pituitary gene expression related to hypothalamo-pituitary-gonadal ( HPG ) axis stimulation as well as increased in vitro responsiveness to gonadotropin releasing hormone ( GnRH ) stimulation in the pituitary when compared to low egg producing hens ( LEPH ). Transcriptome analysis was performed on hypothalamus and pituitary samples from LEPH and HEPH to identify novel regulators of HPG axis function. Results In the hypothalamus and pituitary, 4644 differentially expressed genes ( DEGs ) were identified between LEPH and HEPH, with 2021 genes up-regulated in LEPH and 2623 genes up-regulated in HEPH. In LEPH, up-regulated genes showed enrichment of the hypothalamo-pituitary-thyroid ( HPT ) axis. Beta-estradiol was identified as an upstream regulator regardless of tissue. When LEPH and HEPH samples were compared, beta-estradiol was activated in HEPH in 3 of the 4 comparisons, which correlated to the number of beta-estradiol target genes up-regulated in HEPH. In in vitro pituitary cell cultures from LEPH and HEPH, thyroid hormone pretreatment negatively impacted gonadotropin subunit mRNA levels in cells from both LEPH and HEPH, with the effect being more prominent in HEPH cells. Additionally, the effect of estradiol pretreatment on gonadotropin subunit mRNA levels in HEPH cells was negative, whereas estradiol pretreatment increased gonadotropin subunit mRNA levels in LEPH cells. Conclusions Up-regulation of the HPT axis in LEPH and upstream beta-estradiol activation in HEPH may play a role in regulating HPG axis function, and ultimately ovulation rates. Thyroid hormone and estradiol pretreatment impacted gonadotropin mRNA levels following GnRH stimulation, with the inhibitory effects of thyroid hormone more detrimental in HEPH and estradiol stimulatory effects more prominent in LEPH. Responsiveness to thyroid hormone and estradiol may be due to desensitization to thyroid hormone and estradiol in LEPH and HEPH, respectively, due to up-regulation of the HPT axis in LEPH and of the HPG axis in HEPH. Further studies will be necessary to identify possible target gene desensitization mechanisms and elicit the regulatory role of the HPT axis and beta-estradiol on ovulation rates in turkey hens.