Cardiac transcriptome study of the effect of heat stress in yellow-feather broilers

Transcriptomics analysis unveils key potential genes associated with brain development and feeding behavior in the hypothalamus of L-citrulline-fed broiler chickens

High ambient temperature is a major environmental stressor affecting poultry production, especially in the tropical and subtropical regions of the world. Nutritional interventions have been adopted to combat thermal stress in poultry, including the use of amino acids. L-citrulline is a nonessential amino acid that is involved in nitric oxide generation and thermoregulation, however, the molecular mechanisms behind L-citrulline's regulation of body temperature are still unascertained. This study investigated the global gene expression in the hypothalamus of chickens fed either basal diet or L-citrulline-supplemented diets under different housing temperatures. Ross 308 broilers were fed with basal diet (CON) or 1% L-citrulline diet (LCT) from day-old, and later subjected to 2 environmental temperatures in a 2 by 2 factorial arrangement as follows; basal diet-fed chickens housed at 24°C (CON-TN); L-citrulline diet-fed chickens housed at 24°C (LCT-TN); basal diet-fed chickens housed at 35°C (CON-HS), and L-citrulline diet-fed chickens housed at 35°C (LCT-HS) from 22 to 42 d of age. At 42-days old, hypothalamic tissues were collected for mRNA analyses and RNA sequencing. A total of 1,019 million raw reads were generated and about 82.59 to 82.96% were uniquely mapped to genes. The gene ontology (GO) term between the CON-TN and LCT-TN groups revealed significant enrichments of pathways such as central nervous system development, and Wnt signaling pathway. On the other hand, GO terms between the CON-HS and LCT-HS groups revealed enrichments in the regulation of corticosteroid release, regulation of feeding behavior, and regulation of inflammatory response. Several potential candidate genes were identified to be responsible for central nervous system development (EMX2, WFIKKN2, SLC6A4 Wnt10a, and PHOX2B), and regulation of feed intake (NPY, AgRP, GAL, POMC, and NMU) in chickens. Therefore, this study unveils that L-citrulline can influence transcripts associated with brain development, feeding behavior, energy metabolism, and thermoregulation in chickens raised under different ambient temperatures.

Transcriptome analysis of multiple tissues reveals the potential mechanism of death under acute heat stress in chicken

BACKGROUND

Acute heat stress could induce high mortality and cause huge economic losses in the poultry industry. Although many studies have revealed heat stress-induced injuries of multiple tissues, the main target tissue and molecular mechanism of death under acute heat stress was largely unknown. This study systematically compared the transcriptome data of five main visceral tissues in chickens to reveal the response of multiple tissues to acute heat stress and determine the main target tissue of acute heat stress, further revealing the injuries of main target tissue and their potential mechanism by combing pathological section and qRT-PCR technologies.

RESULTS

The transcriptome data of five visceral tissues revealed that acute heat stress broadly caused inflammatory response and damaged tissues metabolic homeostasis. Among the five tested visceral tissues, the number of differentially expressed genes in the lung was the highest, and their fold changes were the greatest, indicating that the lung was the main target tissue of acute heat stress. The results of pathological section revealed severe inflammation, emphysema and pulmonary hemorrhage in the lung under acute heat stress. Our study found that some pro-inflammatory genes, including CNTFR, FURIN, CCR6, LIFR and IL20RA, were significantly up-regulated both in the heat-stress and heat-death groups, and their fold changes in the heat-death group were significantly greater than that in the heat-stress group. We also found an anti-inflammatory gene, AvBD9, exhibiting an extremely high expression in the heat-stress group but a low expression in the heat-death group.

CONCLUSIONS

Our study found that acute heat stress caused multiple tissue injuries broadly and the lung was the main target tissue of acute heat stress in chicken. Acute heat stress caused a severe inflammatory response, emphysema, and pulmonary haemorrhage, The severe inflammatory response in the heat-death group was related to the up-regulation of pro-inflammatory genes and down-regulation of anti-inflammatory genes.

Global trends and research frontiers on heat stress in poultry from 2000 to 2021: A bibliometric analysis

Background: Heat stress remains a major environmental factor affecting poultry production. With growing concerns surrounding climate change and its antecedent of global warming, research on heat stress in poultry has gradually gained increased attention. Therefore, this study aimed to examine the current status, identify the research frontiers, and highlight the research trends on heat stress in poultry research using bibliometric analysis. Methods: The literature search was performed on the Web of Science Core Collection database for documents published from 2000 to 2021. The documents retrieved were analyzed for their publication counts, countries, institutions, keywords, sources, funding, and citation records using the bibliometric app on R software. Network analysis for co-authorship, co-occurrence, citation, co-citation, and bibliographic coupling was visualized using the VOSviewer software. Results: A total of 468 publications were retrieved, and over the past two decades, there was a gradual increase in the annual number of publications (average growth rate: 4.56%). China had the highest contribution with respect to the number of publications, top contributing authors, collaborations, funding agencies, and institutions. Nanjing Agricultural University, China was the most prolific institution. Kazim Sahin from Firat University, Turkey contributed the highest number of publications and citations to heat stress in poultry research, and Poultry Science was the most productive and the most cited journal. The top 10 globally cited documents mainly focused on the effects of heat stress, alleviation of heat stress, and the association between heat stress and oxidative stress in poultry. All keywords were grouped into six clusters which included studies on "growth performance", "intestinal morphology", "heat stress", "immune response", "meat quality", and "oxidative stress" as current research hotspots. In addition, topics such as; "antioxidants", "microflora", "intestinal barrier", "rna-seq", "animal welfare", "gene expression", "probiotics", "feed restriction", and "inflammatory pathways" were identified for future research attention. Conclusion: This bibliometric study provides a detailed and comprehensive analysis of the global research trends on heat stress in poultry over the last two decades, and it is expected to serve as a useful reference for potential research that will help address the impacts of heat stress on poultry production globally.

iTRAQ-based quantitative proteomic analyses the cycle chronic heat stress affecting liver proteome in yellow-feather chickens

Heat stress (HS) is one of the main environmental factors affecting the efficiency of poultry production. The yellow-feather chickens (YFC) as an indigenous strain of chicken is a popular poultry breed in China. Our previous study used the RNA-seq to analyze the gene expression profiles of male YFC under HS and showed that the lipid and energy metabolism pathways are activated in livers of YFC exposed to acute HS (38°C, 4 h and 25°C recovery 2 h). In this study, we used quantitative proteome analysis based on iTRAQ to study the liver response of YFC to cycle chronic HS (38 ± 1°C, 8 h/d, 7 d, CyCHS). The male YFCs treatment used the CyCHS from 22 to 28 days of age. The liver tissue samples were collected at 28 d old. A total of 39,327 unique peptides matches were detected using iTRAQ analysis and 4,571 proteins exhibited a false discovery rate of 1% or less. Forty-six significant differentially expressed proteins (DEPs) were detected in the CyCHS group compared with the control group for the liver samples, including up- and down-regulated DEPs were 18 and 28, respectively. We found that the enriched biological process terms of the DEPs expressed in the liver were related to DNA metabolic process, oxidation-reduction process, oxidative stress and gluconeogenesis. In KEGG pathway analysis. Most of the hepatic DEPs were annotated to glutathione metabolism and TCA cycle in response to CyCHS. The up-regulation of 5 DEPs (GPX1, GSTT1, GSTT1L, RRM2, and LOC100859645) in the glutathione metabolism pathway likely reflects an attempt to deal with oxidative damage by CyCHS. The down-regulation of 3 DEPs (Isocitrate dehydrogenase [IDH3A], IDH3B, and phosphoenolpyruvate carboxykinase 1) in the TCA cycle pathway contributes to the regulation mechanism of energy metabolism and probably to cope with the balance of heat production and dissipation during CyCHS in order to adapt to high temperature environments. Our results provide insights into the potential molecular mechanism in heat-induced oxidative stress and energy in YFCs and future studies will investigate the functional genes associated with the response to HS.

RNA-Seq Study of Hepatic Response of Yellow-Feather Chickens to Acute Heat Stress

The yellow-feather broiler is a popular poultry breed in Asia, particularly in China. In this study, we performed RNA-seq analysis to identify differentially expressed genes (deGs) in the liver of yellow-feather broilers that had been subjected to acute heat stress treatment (38±1°C for 4 h, recovery 2 h) and determine the response of the liver to high temperature and its effects on yellow-feather broiler physiology. We found that the cloacal temperature and respiratory rate of yellow-feather chickens were significantly increased immediately after the initiation of acute heat stress (38°c) treatment. And after recovery for 2 h, there was no difference in the cloacal temperature and respiratory rate between the acute heat stress and control groups. A total of 834 DEGs were observed in response to heat stress by RNA-seq. Almost half of the DEGs were involved in the lipid and energy metabolism, including fatty acid metabolism (ACOX1, ACACA, ACSL1, ACSL6, ACAA1, ACAA2, HADHB, and FASN) and propanoate metabolism (ACSS2, ALDH2, ACACA, DLAT, ALDH7A1, MDH1, ME1, ABAT, SUCLG2, and ACSS3). Our findings provide the context for RNA-seq studies in the liver of yellow-feather chickens and suggest that the liver of yellow-feather broilers has the lipid and energy metabolism physiological mechanisms activated in response to heat stress.