Heat stress affects duodenal microbial community of indigenous yellow-feather broilers as determined by 16S rRNA sequencing

Whole-genome analysis reveals distinct adaptation signatures to diverse environments in Chinese domestic pigs

BACKGROUND

Long-term natural and artificial selection has resulted in many genetic footprints within the genomes of pig breeds across distinct agroecological zones. Nevertheless, the mechanisms by which these signatures contribute to phenotypic diversity and facilitate environmental adaptation remain unclear.

RESULTS

Here, we leveraged whole-genome sequencing data from 82 individuals from 6 domestic pig breeds originating in tropical, high-altitude, and frigid regions. Population genetic analysis suggested that habitat isolation significantly shaped the genetic diversity and contributed to population stratification in local Chinese pig breeds. Analysis of selection signals revealed regions under selection for adaptation in tropical (55.5 Mb), high-altitude (43.6 Mb), and frigid (17.72 Mb) regions. The potential functions of the selective sweep regions were linked to certain complex traits that might play critical roles in different geographic environments, including fat coverage in frigid environments and blood indicators in tropical and high-altitude environments. Candidate genes under selection were significantly enriched in biological pathways involved in environmental adaptation. These pathways included blood circulation, protein degradation, and inflammation for adaptation to tropical environments; heart and lung development, hypoxia response, and DNA damage repair for high-altitude adaptation; and thermogenesis, cold-induced vasodilation (CIVD), and the cell cycle for adaptation to frigid environments. By examining the chromatin state of the selection signatures, we identified the lung and ileum as two candidate functional tissues for environmental adaptation. Finally, we identified a mutation (chr1: G246,175,129A) in the cis-regulatory region of ABCA1 as a plausible promising variant for adaptation to tropical environments.

CONCLUSIONS

In this study, we conducted a genome-wide exploration of the genetic mechanisms underlying the adaptability of local Chinese pig breeds to tropical, high-altitude, and frigid environments. Our findings shed light on the prominent role of cis-regulatory elements in environmental adaptation in pigs and may serve as a valuable biological model of human plateau-related disorders and cardiovascular diseases.

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.

Effect of heat stress on ileal microbial community of indigenous yellow-feather broilers based on 16S rRNA gene sequencing

Objectives

The broiler chickens are susceptible to heat stress (HS), including the indigenous broilers raised in tropical and subtropical regions. HS caused intestinal dysfunction and disrupted the gut microbiota. However, the researches about the effects of HS on ileal microbiome of indigenous broilers are limited. Therefore, this experiment used 16S rRNA sequencing to analyse the ileal microbial community in indigenous yellow‐feather broilers under HS.

Material and methods

The single factor completely random design was used in the present study, and forty 8‐week‐old Chinese indigenous yellow‐feather broilers (Huaixiang chickens) were randomly divided into two treatments: normal temperature (NT) group and HS group. There are five replications with four broilers per replicate in each group. The broilers in NT group were raised at 21.3 ± 1.2°C during the whole experimental period, the broilers in HS group were exposed to 32.5 ± 1.4°C for 8 h/day from 9:00 am to 17:00 pm and the temperature of rest time is consistent with NT group. The experiment lasted for 4 weeks.

Results

The results showed that HS exposure had no significant effects on the alpha diversity index of ileal microflora of broilers, including the Shannon, Simpson, Chao1 and ACE indexes (p > 0.05). At the genus level, HS significantly reduced the relative abundance of Campylobacter (p < 0.05), and increased the abundance of Delftia (p < 0.05). In addition, prediction of microbial community function indicated that HS significantly enhanced the abundance of the microflora related to lipid metabolism, carbohydrate metabolism and xenobiotics biodegradation and metabolism and reduced the abundance of the microflora related to nucleotide metabolism and amino acid metabolism.

Conclusions

Taken together, the present study revealed that chronic HS (4 weeks) exposure changes the abundance of the ileal microflora of broilers. These findings provided new insights into the role of HS in influencing ileal microbial community in indigenous broilers.