Heat Treatment at an Early Age Has Effects on the Resistance to Chronic Heat Stress on Broilers

Dual stressors of infection and warming can destabilize host microbiomes

Climate change is causing extreme heating events and intensifying infectious disease outbreaks. Animals harbour microbial communities, which are vital for their survival and fitness under stressful conditions. Understanding how microbiome structures change in response to infection and warming may be important for forecasting host performance under global change. Here, we evaluated alterations in the microbiomes of several wild Caenorhabditis elegans isolates spanning a range of latitudes, upon warming temperatures and infection by the parasite Leucobacter musarum. Using 16S rRNA sequencing, we found that microbiome diversity decreased, and dispersion increased over time, with the former being more prominent in uninfected adults and the latter aggravated by infection. Infection reduced dominance of specific microbial taxa, and increased microbiome dispersion, indicating destabilizing effects on host microbial communities. Exposing infected hosts to warming did not have an additive destabilizing effect on their microbiomes. Moreover, warming during pre-adult development alleviated the destabilizing effects of infection on host microbiomes. These results revealed an opposing interaction between biotic and abiotic factors on microbiome structure. Lastly, we showed that increased microbiome dispersion might be associated with decreased variability in microbial species interaction strength. Overall, these findings improve our understanding of animal microbiome dynamics amidst concurrent climate change and epidemics. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Effects of heat stress exposure on porcine muscle satellite cells

Heat stress (HS) affects cell culture as well as animal production. Although there have been many reports on the disparate effects of heat stress, its effects on mammalian muscle stem cells are still unclear. In this study, we isolated porcine muscle satellite cells (PMSCs) from the femurs of 1-day-old piglets, and cultured them under three temperature conditions: 37 °C, 39 °C, and 41 °C. Exposure to HS not only decreased the viability and proliferation rates of PMSCs, but also regulated the cell cycle and induced apoptosis. High-temperature culture conditions decreased both protein and gene expression of Pax7, a proliferation and maintenance marker of muscle satellite cells, whereas it increased both protein and gene expression of MyoG, a differentiation marker, and promoted myotube formation in the early stage of differentiation induction. In addition, the protein and gene expression of several heat shock proteins (HSPs) in PMSCs increased due to heat treatment. In conclusion, HS induced the cell cycle arrest of PMSCs, thereby reducing the proliferation rate. In addition, high-temperature culture conditions promoted the formation of myotubes at the early stage of differentiation of PMSCs without additives.

Effects of Thermal Manipulation on mRNA Regulation of Response Genes Regarding Improvement of Thermotolerance Adaptation in Chickens during Embryogenesis

The phenomenon of increasing heat stress (HS) among animals is of particular significance when it is seen in economically significant industries, such as poultry. Due to the identification of the physiological, molecular, and genetic roots of HS responses in chickens, a substantial number of studies have focused on reducing the effects of HS in poultry through environmental management, dietary manipulation, and genetic alterations. Temperature manipulation (TM) during embryogenesis has been claimed to increase the thermal tolerance and well-being of chickens without affecting their capacity for future growth. There has been little investigation into the vulnerability of the epigenome involving TM during embryogenesis, although the cellular pathways activated by HS have been explored in chickens. Epigenetic changes caused by prenatal TM enhance postnatal temperature adaption and produce physiological memory. This work offers a thorough analysis that explains the cumulative impact of HS response genes, such as genes related to heat shock proteins, antioxidants, and immunological genes, which may aid in the enhanced adaptability of chickens that have undergone thermal manipulation during their embryonic stages.

Effect of thermal conditioning on growth performance and thermotolerance in broilers: A systematic review and meta-analysis

Thermal conditioning has been introduced as a cost-effective way to improve performance and thermotolerance in broilers. However, since all the trials were performed under various experimental conditions, it appears difficult to draw general conclusions. Therefore, the objective of this study was to quantify the response of broilers to thermal conditioning through a meta-analysis approach. A literature search was conducted on Scopus, PubMed, Scielo, Web of Science, and Google scholar in December 2020. A restricted maximum likelihood random effect model was used to pool the effect sizes from the body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR), and body temperature (Tb). BWG, FI, and Tb were computed using the standardized mean difference (SMD) while FCR was computed using mean differences (MD) with a 95% confidence interval (IC). Growth performances were evaluated during the thermoneutral conditions while Tb was evaluated after either acute or chronic heat stress after early age thermal conditioning. A total of 17 studies were included in the dataset. Thermal conditioning significantly increased BWG (SMD = 0.139, IC = 0.0372-0.2407, P = 0.0074) and FI (SMD = 0.292, IC = 0.108-0.476, P = 0.0019) compared with the control. Additionally, subgroup analysis revealed that overall Tb was significantly reduced under acute heat stress (SMD = -0.455, IC = -0.718 to -0.192, P < 0.001) but not affected during chronic heat stress (SMD = -0.115, IC = -0.651 to -0.420, P = 0.6729). In conclusion, thermal conditioning significantly increased the broiler's BWG and FI under thermoneutral conditions and can help in reducing Tb under acute heat stress.

Tryptophan in poultry nutrition: Impacts and mechanisms of action

Many studies have shown that productivity, immune system, antioxidant status, and meat and egg quality can be optimized by dietary supplementation with amino acids that are not usually added to poultry diets. Understanding the effects of these amino acids may encourage feed manufacturers and poultry producers to include them as additives. One of these amino acids is tryptophan (Trp). The importance of Trp is directly related to its role in protein anabolism and indirectly related to its metabolites such as serotonin and melatonin. Thus, Trp could affect the secretion of hormones, development of immune organs, meat and egg production, and meat and egg quality in poultry raised under controlled or stressed conditions. Therefore, this review discusses the main roles of Trp in poultry production and its mode (s) of action in order to help poultry producers decide whether they need to add Trp to poultry diets. Further areas of research are also identified to address information gaps.

Genome-wide identification and functional prediction of long non-coding RNAs in Sprague-Dawley rats during heat stress

Background

Heat stress (HS) is a major stress event in the life of an animal, with detrimental upshots in production and health. Long-non-coding RNAs (lncRNAs) play an important role in many biological processes by transcriptional regulation. However, no research has been reported on the characterization and functionality of lncRNAs in heat-stressed rats.

Results

We studied expression levels of lncRNAs in rats during HS, using strand-specific RNA sequencing. Six rats, three in each of Control (22 ± 1 °C) and H120 (42 °C for 120 min) experimental groups, were used to screen for lncRNAs in their liver and adrenal glands. Totally, 4498 and 7627 putative lncRNAs were identified in liver and adrenal glands of the Control and H120 groups, respectively. The majority of lncRNAs were relatively shorter and contained fewer exons than protein-coding transcripts. In total, 482 (174 up-regulated and 308 down-regulated) and 271 (126 up-regulated and 145 down-regulated) differentially-expressed lncRNAs (DElncRNAs, P < 0.05) were identified in the liver and adrenal glands of the Control and H120 groups, respectively. Furthermore, 1274, 121, and 73 target differentially-expressed genes (DEGs) in the liver were predicted to interact with DElncRNAs based on trans−/cis- and sequence similarity regulatory modes. Functional annotation analyses indicated that these DEGs were mostly significantly enriched in insulin signalling, myeloid leukaemia, and glucagon signalling pathways. Similarly, 437, 73 and 41 target DEGs in the adrenal glands were mostly significantly enriched in the cell cycle (trans-prediction) and lysosome pathways (cis-prediction). The DElncRNAs interacting with DEGs that encode heat shock proteins (HSPs) may play an important role in HS response, which include Hsf4, Dnaja1, Dnajb4, Hsph1 and Hspb1 in the liver, and Dnajb13 and Hspb8 in the adrenal glands. The strand-specific RNA sequencing findings were also further verified through RT-qPCR.

Conclusions

This study is the first to provide a detailed characterization and functional analysis of expression levels of lncRNAs in liver and adrenal glands of heat-stressed rats, which provides basis for further studies on the biological functions of lncRNAs under heat stress in rats and other mammalian species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07421-8.

Broiler production challenges in the tropics: A review

Under tropical climate, broiler production is encumbered by several constraints which make it difficult for them to attain their genetic potential. The scarcity and high price of poultry feed and veterinary services and the harsh environmental conditions with respect to thermal stress are some of the challenges that hinder optimal growth of the birds. Limited availability of feedstuffs, including crucial feed ingredients like maize and oil seedcakes, is an important challenge to the sector, since feed still represents a major cost of producing broiler chickens. Additionally, the problem of climate change, which has become a global concern, is the main problem in broiler production under hot and humid climate. Under high ambient temperature, feed intake decreases, carbohydrates metabolism and protein synthesis efficiency are disturbed. Lipid utilization is lower and glucose or insulin homeostasis is altered while fat deposition and oxidative stress increases. Several strategies are used to ameliorate the effect of heat stress in poultry. The objective of this review was to summarize the challenge in broiler production under hot and humid climate and different approaches to fight heat stress in poultry.

Proteomic Analysis of the Protective Effect of Early Heat Exposure against Chronic Heat Stress in Broilers

Simple Summary

Heat stress affects the livestock industry, especially in poultry. Screening for metabolic changes after early and chronic heat exposure in poultry would be beneficial in resolving the production issues. In this study, we identified differentially expressed proteins that affected early heat exposure during chronic heat stress. Chronic heat stress affected 277 proteins, of which 95 differed in expression by early heat exposure. Differentially expressed proteins were related to actin metabolism and also involved in carbohydrate and carbon metabolism. According to our results, early heat exposed liver of broilers activates the different physiological mechanisms for protection from later heat stress.

Abstract

The increasing trend of global warming has affected the livestock industry through the heat stress, especially in poultry. Therefore, a better understanding of the mechanisms of heat stress in poultry would be helpful for maintaining the poultry production. Three groups were designed to determine early heat stress effects during chronic heat stress: CC, raised at a comfortable temperature; CH, chronic heat exposure at 35 °C for 21–35 days continuously; and HH, early heat exposure at 40 °C for 24 h at 5 days old with 35 °C temperature for 21–35 days continuously. In this study, proteome analysis was carried out to identify differentially expressed proteins in the liver tissue of broilers under chronic and early heat exposure. There were eight differentially expressed proteins from early heat stress during chronic heat exposure, which were related to actin metabolism. According to KEGG (Kyoto encyclopedia of genes and genomes) analysis, the proteins involved in carbohydrate metabolism were expressed to promote the metabolism of carbohydrates under chronic heat stress. Early heat reduced the heat stress-induced expression changes of select proteins. Our study has shown that early heat exposure suggests that the liver of broilers has various physiological mechanisms for regulating homeostasis to aid heat resistance.

RNA seq analyses of chicken reveals biological pathways involved in acclimation into different geographical locations

Transcriptome expression reflects genetic response in diverse conditions. In this study, RNA sequencing was utilized to profile multiple tissues such as liver, breast, caecum, and gizzard of Korean commercial chicken raised in Korea and Kyrgyzstan. We analyzed ten samples per tissue from each location to identify candidate genes which are involved in the adaptation of Korean commercial chicken to Kyrgyzstan. At false discovery rate (FDR) < 0.05 and fold change (FC) > 2, we found 315, 196, 167 and 198 genes in liver, breast, cecum, and gizzard respectively as differentially expressed between the two locations. GO enrichment analysis showed that these genes were highly enriched for cellular and metabolic processes, catalytic activity, and biological regulations. Similarly, KEGG pathways analysis indicated metabolic, PPAR signaling, FoxO, glycolysis/gluconeogenesis, biosynthesis, MAPK signaling, CAMs, citrate cycles pathways were differentially enriched. Enriched genes like TSKU, VTG1, SGK, CDK2 etc. in these pathways might be involved in acclimation of organisms into diverse climatic conditions. The qRT-PCR result also corroborated the RNA-Seq findings with R² of 0.76, 0.80, 0.81, and 0.93 for liver, breast, caecum, and gizzard respectively. Our findings can improve the understanding of environmental acclimation process in chicken.

Muscle Antioxidant Activity and Meat Quality Are Altered by Supplementation of Astaxanthin in Broilers Exposed to High Temperature

This study investigated the effect of dietary astaxanthin (AST) on the meat quality, antioxidant status, and immune response of chickens exposed to heat stress. Four hundred and eighty male broilers were assigned to four treatments including AST0, AST20, AST40, and AST80 with 0, 20, 40, and 80 ppm astaxanthin supplementation levels, respectively. There was a linear decrease of malondialdehyde (MDA) in leg muscle. Catalase and superoxide dismutase levels in the plasma were linearly increased. There was a linear increase in the level of total antioxidant capacity in the leg muscle. The 3-ethylbenzothiazoline-6-sulfonate reducing activity of leg muscle was significantly increased in the AST80 treatment. The AST40 treatment showed an increase in 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity of leg muscles. Breast meat redness and yellowness were linearly increased. The astaxanthin-supplemented treatments exhibited lower drip loss and MDA concentration of leg muscle compared with the AST0 treatment at days 3 and 9 of storage. Supplementation of 40 or 80 mg/kg astaxanthin significantly decreased heat shock protein (HSP)27, HSP70, tumor necrosis factor alpha, and interleukin-6 expression in the livers. The feather corticosterone was significantly lower in the astaxanthin-supplemented treatments than in the AST0 treatment. In conclusion, astaxanthin decreased the hyperthermic stress level and improved meat quality, and antioxidant status of chickens exposed to heat stress.