Abstract
BackgroundHigh ambient temperatures cause stress in poultry, especially for broiler lines, which are genetically selected for rapid muscle growth. RNA-seq technology provides powerful insights into environmental response from a highly metabolic tissue, the liver. We investigated the effects of acute (3 h, 35 °C) and chronic (7d of 35 °C for 7 h/d) heat stress on the liver transcriptome of 3-week-old chicks of a heat-susceptible broiler line, a heat-resistant Fayoumi line, and their advanced intercross line (AIL).ResultsTranscriptome sequencing of 48 male chickens using Illumina HiSeq 2500 technology yielded an average of 33.9 million, 100 base-pair, single-end reads per sample. There were 8 times more differentially expressed genes (DEGs) (FDR < 0.05) in broilers (n = 627) than Fayoumis (n = 78) when comparing the acute-heat samples to the control (25 °C) samples. Contrasting genetic lines under similar heat treatments, the highest number of DEGs appeared between Fayoumi and broiler lines. Principal component analysis of gene expression and analysis of the number of DEGs suggested that the AIL had a transcriptomic response more similar to the Fayoumi than the broiler line during acute heat stress. The number of DEGs also suggested that acute heat stress had greater impact on the broiler liver transcriptome than chronic heat stress. The angiopoietin-like 4 (ANGPTL4) gene was identified as differentially expressed among all 6 contrasts. Ingenuity Pathway Analysis (IPA) created a novel network that combines the heat shock protein family with immune response genes.ConclusionsThis study extends our understanding of the liver transcriptome response to different heat exposure treatments in distinct genetic chicken lines and provides information necessary for breeding birds to be more resilient to the negative impacts of heat. The data strongly suggest ANGPTL4 as a candidate gene for improvement of heat tolerance in chickens.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3291-0) contains supplementary material, which is available to authorized users.
Highlights
High ambient temperatures cause stress in poultry, especially for broiler lines, which are genetically selected for rapid muscle growth
Chicken liver transcriptome alignment and mapping A little more than 1.6 billion, 100-base single-end reads were produced from the single chip run on the Illumina HiSeq 2500 platform
Principle component analysis (PCA) results show the 3 genetic lines separated with the advanced intercross line (AIL) located in the middle, between its two parental lines
Summary
High ambient temperatures cause stress in poultry, especially for broiler lines, which are genetically selected for rapid muscle growth. Climate change negatively impacts animals, resulting in significant welfare concerns and economic losses in livestock industries [1, 2]. Heat stress causes an estimated economic loss of more than onehundred million dollars annually for the US poultry industry. Decades of selection for muscle accretion have resulted in broilers that have excellent performance in economic traits, but do not acclimatize well to stressful environmental conditions such as high temperature and humidity [3,4,5]. It has been difficult to develop broiler genetics for adaptation to climate change while maintaining high performance.
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