BackgroundIn broilers, high ambient temperature can result in reduced feed consumption, digestive inefficiency, impaired metabolism, and even death. The broiler sector of the U.S. poultry industry incurs approximately $52 million in heat-related losses annually. The objective of this study is to characterize the effects of cyclic high ambient temperature on the transcriptome of a metabolically active organ, the liver. This study provides novel insight into the effects of high ambient temperature on metabolism in broilers, because it is the first reported RNA-seq study to characterize the effect of heat on the transcriptome of a metabolic-related tissue. This information provides a platform for future investigations to further elucidate physiologic responses to high ambient temperature and seek methods to ameliorate the negative impacts of heat.ResultsTranscriptome sequencing of the livers of 8 broiler males using Illumina HiSeq 2000 technology resulted in 138 million, 100-base pair single end reads, yielding a total of 13.8 gigabases of sequence. Forty genes were differentially expressed at a significance level of P-value < 0.05 and a fold-change ≥ 2 in response to a week of cyclic high ambient temperature with 27 down-regulated and 13 up-regulated genes. Two gene networks were created from the function-based Ingenuity Pathway Analysis (IPA) of the differentially expressed genes: “Cell Signaling” and “Endocrine System Development and Function”. The gene expression differences in the liver transcriptome of the heat-exposed broilers reflected physiological responses to decrease internal temperature, reduce hyperthermia-induced apoptosis, and promote tissue repair. Additionally, the differential gene expression revealed a physiological response to regulate the perturbed cellular calcium levels that can result from high ambient temperature exposure.ConclusionsExposure to cyclic high ambient temperature results in changes at the metabolic, physiologic, and cellular level that can be characterized through RNA-seq analysis of the liver transcriptome of broilers. The findings highlight specific physiologic mechanisms by which broilers reduce the effects of exposure to high ambient temperature. This information provides a foundation for future investigations into the gene networks involved in the broiler stress response and for development of strategies to ameliorate the negative impacts of heat on animal production and welfare.

Nutritional modulation of the immune system is an often exploited but poorly characterized process. In chickens and other food production animals, dietary enhancement of the immune response is an attractive alternative to antimicrobial use. A yeast cell wall component, beta-1,3/1,6-glucan, augments the response to disease in poultry and other species; however, the mechanism of action is not clear. Ascorbic acid and corticosterone are better characterized immunomodulators. In chickens, the spleen acts both as reservoir and activation site for leukocytes and, therefore, splenic gene expression reflects systemic immune function. To determine effects of genetic line and dietary immunomodulators, chickens of outbred broiler and inbred Leghorn and Fayoumi lines were fed either a basal diet or an experimental diet containing beta-glucans, ascorbic acid, or corticosterone from 56 to 77 d of age. Spleens were harvested, mRNA was isolated, and expression of interleukin (IL)-4, IL-6, IL-18, macrophage inflammatory protein-1beta, interferon-gamma, and phosphoinositide 3-kinase p110gamma transcripts was measured by quantitative reverse transcription PCR. Effects of diet, genetic line, sex, and diet x genetic line interaction on weight gain and gene expression were analyzed. At 1, 2, and 3 wk after starting the diet treatments, birds fed the corticosterone diet had gained less weight compared with birds fed the other diets (P < 0.001). Sex affected expression of IL-18 (P = 0.010), with higher levels in males. There was a significant interaction between genetic line and diet on expression of IL-4, IL-6, and IL-18 (P = 0.021, 0.006, and 0.026, respectively). Broiler line gene expression did not change in response to the experimental diet. Splenic expression of IL-6 was higher in Leghorns fed the basal or ascorbic acid diets, rather than the beta-glucan or corticosterone diets, whereas the opposite relationship was observed in the Fayoumi line. Expression of IL-4 and IL-18 responded to diet only within the Fayoumi line. The differential splenic expression of birds from diverse genetic lines in response to nutritional immunomodulation emphasizes the need for further study of this process.

Chicken meat and eggs contaminated with Salmonella result in economic losses in the poultry industry and potential human infection. Intestinal parasites have been shown to lead to a reduction in the utilization of nutrients and performance in poultry. This study provides insight into the immune responses used by hens of 3 genetically distinct chicken lines (broiler, Leghorn, and Fayoumi) in the presence and absence of Salmonella Enteritidis infection. Understanding the range of immune responses used by different lines in response to Salmonella Enteritidis may help the poultry industry genetically select birds that are more pathogen resistant. The splenic mRNA levels of several immune-related genes [IL-6, IL-8, IL-10, IL-18, macrophage inflammatory protein 1β, interferon (IFN)-γ, transforming growth factor β1, and regulated upon activation, normal T cell expressed, and secreted (RANTES)] were analyzed by quantitative PCR. Line, challenge, and their interaction were considered fixed effects. Line had a significant effect on the mRNA expression of RANTES (P < 0.02) and IFN-γ (P < 0.03). Broilers expressed significantly more splenic RANTES mRNA than Fayoumis, and significantly more splenic IFN-γ mRNA than Leghorns (P < 0.05). There was a significant interaction of genetic line and challenge on IL-18 (P < 0.02) and IL-6 (P < 0.01) mRNA expression. Although there was a significant interaction of genetic line and challenge for IL-18, Tukey's test analysis only showed differences at a suggestive level (P < 0.1). Bacterial challenge had a significant effect on IL-6 mRNA expression only within the Fayoumi line. Challenged Fayoumis expressed significantly less IL-6 mRNA than nonchallenged Fayoumis (P < 0.05). The observed differences in mRNA expression of selected cytokines support the concept that these distinct genetic lines utilize different immune responses at homeostasis and in response to Salmonella Enteritidis infection.

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Summary: Salmonella enterica serovar enteritidis is an enteric bacterium that can contaminate chicken eggs and meat, resulting in production losses and consumer illness. To provide insight into the systemic metabolic effects of S. enteritidis infection, liver samples were harvested 10-days postinfection from broiler hens. Hepatic global gene expression levels were assessed using a chicken 44K Agilent microarray. Forty-four genes were differentially expressed at a significance level of q value < 0.05. One hundred eighty-three genes were differentially expressed at a suggestive significance level of q value < 0.1. A predominance of downregulation existed among significantly differentially expressed genes. Cell cycle and metabolism networks were created from the differentially expressed genes. Mitochondria-mediated apoptosis, electron transport, peptidase activity, vein constriction, cell differentiation, IL-2 signaling, Jak-Stat signaling, B-cell receptor signaling, GDP/GTP exchange, and protein recycling were among the functions of the differentially expressed genes that were down-regulated in response to S. enteritidis. The effects of S. enteritidis infection on the liver transcriptome profiles of broilers reflect a predominance of downregulation of genes with cell cycle and metabolic functions. The most pronounced response was the downregulation of genes that function in metabolic pathways, inflammation, and mitochondria-mediated apoptosis. These results provide insight into important systemic metabolic mechanisms that are active in the chicken liver in response to S. enteritidis infection at 10-days postinfection. genesis 51: [357][358][359][360][361][362][363][364] 2013. V V C 2012 Wiley Periodicals, Inc.