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Broiler chickens are particularly sensitive to heat exposure during growth, with socio-economic consequences for poultry industry. An embryonic heat acclimation technique was developed to improve chicken long-term heat tolerance (PIESTUN et al., 2008). This thermal manipulation (TM) consists of a rise in temperature during the incubation of eggs 12 h/d from day 7 to 16 of incubation. TM was notably shown to change the thyroid axis regulation in the long term. Chickens resistance to an acute heat challenge was improved at slaughter age. The glucose-insulin balance of birds was also modified (LOYAU et al., 2013). The aim of this work was to better understand in vitro the involvement of the thyroid hormone triiodothyronine (T3) and of insulin in the regulation of metabolic pathways affecting in vivo energy and protein utilization as well as muscle growth in TM Pectoralis major (LOYAU et al., 2014). To identify T3 and insulin effects in interaction to incubation condition, we measured by qRTPCR the expression of candidate genes involved in metabolism and muscle growth, in the regulation of muscle thyroid hormone concentrations and of oxidative stress. Signaling pathways regulating protein synthesis were also studied by biochemical method. The study was carried out both at proliferative (myoblasts) and differentiation (myotubes) cell stages in cells derived from muscle Pectoralis major of chicks submitted to the embryonic treatment TM or not. In our study, TM stimulated pathways that promote proteosynthesis and modified a signaling pathway controlling cellular stress (P38 mitogen activated protein kinase). The TM also affected the regulation of energy metabolism. Indeed, the expression of Peroxisome proliferator activated receptor coactivator 1α (PGC-1α) gene involved in muscle cell energy metabolism was increased in TM as compared to control myoblasts. Apart from the observed effects of incubation conditions, direct effects of hormones were observed. T3 hormone had contrasting effects on the AKT/S6K1 (S6 kinase 1)/S6 (ribosomal protein) pathway, likely stimulating proteosynthesis in myotubes. It also increased the expression of deiodinase 3 promoting T3 conversion to T2 (diiodothyronine). Insulin activated the AKT/S6K1/S6 pathway in both cell types and stimulated the expression of genes involved in the use of energy nutrient such as Citrate Synthase, key enzyme of the Krebs cycle, and β hydroxyacyl-Coa dehydrogenase controlling fatty acid oxidation. Furthermore, insulin interacted with incubation condition to stimulate mitochondrial metabolism via greater PGC-1α expression in TM myotubes only. In conclusion, the in vitro study of TM-derived muscle cells revealed physiological and metabolic modifications promoting protein synthesis and energy use consecutive to embryo heat acclimation treatment in birds that were maintained through cell mitosis. Our results suggest programming mechanisms controlling gene expression under the effect of environment. We speculate that epigenetic alterations could be involved. [ABSTRACT FROM AUTHOR]

Reduction in feed intake is a common physiological response of growing pigs facing stressful environmental conditions. The present experiment aims to study (1) the effects of a short-term feed restriction and refeeding on pig performance and metabolism and (2) the differential response between two breeds, Large White (LW), which has been selected for high performance, and Creole (CR), which is adapted to tropical conditions. A trial of 36 castrated male pigs (18 LW and 18 CR) was carried out. For each breed, half of the animals were restrictively fed at 50% of the standard feed allowance for 6 days and then fed normally for the next 14 days. Growth performance, thermoregulatory responses, plasma hormones and metabolites were measured. Results showed that, for all traits, the difference in response between the two breeds was small and rarely significant, which may be due to the short duration of the feed restriction. Irrespective of breed, feed restriction induced a reduction of growth rate and feed efficiency that was rapidly compensated for upon refeeding. Feed restriction also reduced skin temperature, rectal temperature and respiratory rate, as well as blood urea and cholesterol, which are of interest as potential biomarkers for feed restriction.

Background: Meat type chickens have limited capacities to cope with high environmental temperatures, this sometimes leading to mortality on farms and subsequent economic losses. A strategy to alleviate this problem is to enhance adaptive capacities to face heat exposure using thermal manipulation (TM) during embryogenesis. This strategy was shown to improve thermotolerance during their life span. The aim of this study was to determine the effects of TM (39.5 °C, 12 h/24 vs 37.8 °C from d7 to d16 of embryogenesis) and of a subsequent heat challenge (32 °C for 5 h) applied on d34 on gene expression in the Pectoralis major muscle (PM). A chicken gene expression microarray (8 × 60 K) was used to compare muscle gene expression profiles of Control (C characterized by relatively high body temperatures, Tb) and TM chickens (characterized by a relatively low Tb) reared at 21 °C and at 32 °C (CHC and TMHC, respectively) in a dye-swap design with four comparisons and 8 broilers per treatment. Real-time quantitative PCR (RT-qPCR) was subsequently performed to validate differential expression in each comparison. Gene ontology, clustering and network building strategies were then used to identify pathways affected by TM and heat challenge., Results: Among the genes differentially expressed (DE) in the PM (1.5 % of total probes), 28 were found to be differentially expressed between C and TM, 128 between CHC and C, and 759 between TMHC and TM. No DE gene was found between TMHC and CHC broilers. The majority of DE genes analyzed by RT-qPCR were validated. In the TM/C comparison, DE genes were involved in energy metabolism and mitochondrial function, cell proliferation, vascularization and muscle growth; when comparing heat-exposed chickens to their own controls, TM broilers developed more specific pathways than C, especially involving genes related to metabolism, stress response, vascularization, anti-apoptotic and epigenetic processes., Conclusions: This study improved the understanding of the long-term effects of TM on PM muscle. TM broilers displaying low Tb may have lower metabolic intensity in the muscle, resulting in decreased metabolic heat production, whereas modifications in vascularization may enhance heat loss. These specific changes could in part explain the better adaptation of TM broilers to heat.

Fast-growing chickens have a limited ability to tolerate high temperatures. Thermal manipulation during embryogenesis (TM) has previously been shown to lower chicken body temperature (Tb) at hatching and to improve thermotolerance until market age, possibly resulting from changes in metabolic regulation. The aim of this study was to evaluate the long-term effects of TM (12 h/d, 39.5°C, 65% RH from d 7 to 16 of embryogenesis vs. 37.8°C, 56% RH continuously) and of a subsequent heat challenge (32°C for 5 h at 34 d) on the mRNA expression of metabolic genes and cell signaling in the Pectoralis major muscle and the liver. Gene expression was analyzed by RT-qPCR in 8 chickens per treatment, characterized by low Tb in the TM groups and high Tb in the control groups. Data were analyzed using the general linear model of SAS considering TM and heat challenge within TM as main effects. TM had significant long-term effects on thyroid hormone metabolism by decreasing the muscle mRNA expression of deiodinase DIO3. Under standard rearing conditions, the expression of several genes involved in the regulation of energy metabolism, such as transcription factor PGC-1α, was affected by TM in the muscle, whereas for other genes regulating mitochondrial function and muscle growth, TM seemed to mitigate the decrease induced by the heat challenge. TM increased DIO2 mRNA expression in the liver (only at 21°C) and reduced the citrate synthase activity involved in the Krebs cycle. The phosphorylation level of p38 Mitogen-activated-protein kinase regulating the cell stress response was higher in the muscle of TM groups compared to controls. In conclusion, markers of energy utilization and growth were either changed by TM in the Pectoralis major muscle and the liver by thermal manipulation during incubation as a possible long-term adaptation limiting energy metabolism, or mitigated during heat challenge.

Among the methods generally used to solve a problem in the domain of acoustic radiation, the equivalent sources method offers an interesting alternative. It consists in replacing the vibrating surface with a distribution of acoustic sources placed inside the structure. The contribution of each source is determined in such a way that the acoustic field radiated by these sources verifies the same boundary conditions on the structure. The number of unknowns in the problem is no longer directly linked to the number of mesh points on the structure, as with boundary elements methods, but to the number of equivalent sources employed in the model. The equivalent source method is therefore of major interest if the acoustic radiation of the structure can be approximated with a sufficiently low number of sources. This paper proposes its application when the equivalent source is a sphere. In this case, the number of unknowns is equal to the number of modes. In contrast to the one-point multipole, the sphere has a surface surrounding a closed volume to express the boundary conditions. Although sphere/multipole equivalence has been demonstrated, the surface of the sphere allows normalization of the functions used, leading to stabilization of the system to be resolved. First, the main acoustic radiation characteristics of a sphere and of the linear system verified by the modal coefficients of an equivalent sphere are presented. The different parameters of the model are then studied: position and radius of the equivalent sphere, truncation of the series, and influence of the spatial sampling (mesh). In the same vein, a second approach is presented. It consists of making each point of the structure correspond to a point of the sphere, and the vibrating field at the surface of the sphere is deduced from that of the structure by simple geometric projection. Results can be obtained very quickly as no matrix inversion is required. The accuracy of the results depends on the distance between the sphere and the structure. Finally, an experimental validation that uses both methods is presented and shows interesting results when the structure is closed, and when its shape is not too far removed from a sphere.