Extended Abstract Background: Rapid growth of broilers leads to insufficient cardiac output, cardiac hypertrophy, and finally sudden death. When livestock are exposed to hot environments, they often try to dissipate Heat by increasing blood flow to the skin. This physiological response is a way for animals to adapt to long-term thermal conditions. However, this thermoregulatory mechanism has its limitations. While different animals have varying degrees of tolerance to Heat stress, the cardiovascular system can only compensate within a certain range before it starts to impact food production. Domestic poultry, such as chickens, lack sweat glands, which is a key mechanism for body cooling in many other animals. This deficiency forces the cardiovascular system to work harder, sending more blood to the skin to help regulate body temperature. Broilers, in particular, have a narrow thermoneutral zone (the range of temperatures where an animal can maintain its body temperature without expending extra energy) and a high metabolic rate, which places an even greater burden on their cardiac function. Therefore, it is an appropriate model for studying cardiac disease. Heat stress is among the stressors affecting cardiac performance. In accordance with the cardiac system susceptibility of poultry to Heat stress, especially broilers because of their fast growth rate, to enhance the ability of modern broiler chickens to withstand Heat stress through selective breeding, we need to identify the crucial genes and biological processes that lead to unbalanced heart development and the high incidence of Heat-induced heart problems. Thus, the aim was to consider the gene expression of cardiac contractility proteins under Heat stress conditions during the growing period of broilers. Methods: Ross 708 broilers were subjected to Heat stress (HS) of 35–37 °C for 8 hours daily for 21 days post-hatch. Initially, male broilers had unrestricted access to feed and water in spacious colony houses maintained at 33 °C, with the temperature gradually decreasing by 3 °C per week until it reached 24 °C by the day 21 post-hatch. At the conclusion of the growth period, the broilers were euthanized, and their left ventricles were isolated for mRNA extraction. RNA-seq data were obtained from NCBI’s with the accession number SRP082125. All the expressions of deferentially expressed genes (DEGs) were determined and analyzed by DAVID online bioinformatics tools. Gene ontology qualification, including biological processes (BP), cellular component (CC), and molecular role (MF), were achieved from DAVID. Heat stress induction was from days 21-42 for 8 hours every day for 21 days until to end of the growing period. Results: Gene expression changes were related to 35 genes of the muscular cardiocyte of the left ventricle. From seven genes related to the protein of troponin, TNN and TNNI1 genes, declined significantly, with an increase in the TNNT3 gene expression (P< 0.05). Of five genes related to the tropomyosin protein, the TPM1 gene showed a significant increase in expression (P < 0.05). Of the two genes related to the ryanodine receptor, RYR3 had significant gene upregulation (P < 0.05). From the ten genes related to DHPR, only CACNA2D2 had significant downregulation (P < 0.05). Among four calmodulin-related genes, CAMKK1 and CAMK1D showed significant downregulation, and CAMSAP2 revealed upregulation (P< 0.05). Significant reductions occurred in the expression of five associated genes of heavy-chain myosin (P< 0.05). Conclusion: Heat stress reduced gene expression of ryanodine, DHPR, and troponin, those related to calcium release into the cell cytosol. Furthermore, it prevents cardiac hypertrophy by decreasing the expression of genes related to the heavy chain of myosin. Thus, the vulnerability of modern broilers to heart problems, when exposed to high temperatures, may be linked to their heart's reduced capacity, which is likely due to their relatively smaller heart size. According to genetic analysis, the smaller heart size in broilers under Heat stress than those in a comfortable temperature environment is likely caused by slower cell growth and division. This research identifies specific genes and biological pathways that could be targeted through breeding to develop broilers that are more resistant to Heat stress and have healthier hearts. This study has identified specific genes and biological processes linked to the reduction in heart size observed in broiler chickens subjected to Heat stress. These insights provide new opportunities for developing targeted breeding strategies to address this issue. The findings indicate that selective breeding, by focusing on the identified genes and pathways, may enable the development of broiler chickens that are more resistant to Heat stress and have healthier hearts. By concentrating on these genetic factors, breeders can work toward creating broiler populations that are more resilient to high temperatures and less susceptible to heart problems.

Background: The purpose of this study was to determine the level of Heat stress to construction workers using Thermal Work Limit (TWL) and Wet Bulb Globe Temperature (WBGT) indices and by measuring Urine Specific Gravity (USG) among construction workers in Iran and comparing the appropriateness of these indices for measuring Heat stress in Iran climate.Methods: This comparative and experimental study was conducted during September 2012 in Baghe Ketabe Tehran, one of the large size construction sites in Tehran City, Iran. Sixty participants were randomly selected in two groups (exposed to sun and non-exposed) among the construction workers in a construction campus with similar work type, climate and diet. TWL and WBGT and USG were measured in two consequent days and at the beginning, mid and end of the work shift, for both groups.Results: The mean WBGT index was 22.6±0.9oC for control group and 27.5±1.2oC for exposure group, the mean TWL index measure was 215.8±5.2 W/m2 for control group and 144±9.8 W/m2 for exposure group and the mean USG was 1.0213±0.0054 in control group and 1.026±0.005 in exposure group. There was a significant difference in TWL, WBGT and USG between exposed and non-exposed group (P<0.01).Conclusion: workers were at an allowed level of Heat stress. TWL, WBGT and USG measures were significantly correlated; however as TWL level enabled classification based on required intervention, it had some merit over WBGT index.

Climate changes in recent years have led to an increase in the average of global temperature and the occurrence of temperature anomalies. The research report shows that the increase in temperature resulting from climate change may reduce the yield of wHeat by 5. 5% globally. Heat stress has a negative effect on plant physiological processes such as photosynthesis, respiration, stomatal exchange, absorption of water and nutrients and it’, s processing in the plant, as well as nitrogen metabolism, which leads to the limitation of photosynthetic resources and the reduction of biological and grain yield. Research shows that wHeat cultivars show different reactions to these physiological changes and use different mechanisms such as Heat shock proteins to withstand stress. Introduction of genotypes adapted to Heat stress conditions is one of the important goals of breeding programs. The results of research in the past years show that selection based on physiological traits has increased the efficiency of breeding programs in order to produce genotypes adapted to Heat stress. To explain the effectiveness of physiology knowledge in breeding programs based on target environments, it is necessary to explain the effect of stress on plant physiology, tolerance mechanisms and traits related to these mechanisms. Knowing about the physiological aspects of the plant in response to environmental stresses helps researchers to achieve high production potentials and introduce cultivars tolerant to adverse environmental conditions. In this research, the effect of Heat stress on each of the physiological characteristics and different stages of growth and development of wHeat has been investigated.

Introduction: One ways to prevent Heat stress illness and protect workers is regional and national legislation and international standards about Heat stress. If these regulations and standards are implemented correctly, they can be very effective and efficient. The aim of this review research was studying the importance of Heat stress, the ways of prevention of Heat related illnesses based on the emphasis on the regulations and standards of Heat stress.Methods: In this review study some keywords, including "regulations, standards and thermal stress" using literature search was retrieved, in different occupational health and safety websites such as Safe Work Australia, OSHA, NIOSH and other international organizations during the period from 1992 to 2014.Conclusion: The results showed that legislations and standards are positive steps towards the prevention of Heat stress illness in developed and developing countries, unfortunately, some problems occur when running the requirements. Many employers are concerned about the costs that they must paid to their workers due to the Heat related illness, and often looking for a legal way to avoid paying it. Although with legislations and standards about Heat stress, the workers can complain to the legal authorities in the absence of preventive measures and salary, complain to the authorities, but they rarely do it because of fear of losing their jobs. So, legislations, especially in developing countries do not have enough efficiency and remain only as a document.

Dear Editor-in-Chief Exposure to extreme Heat has been found to be hazardous agent to health, and it has been linked to a range of illnesses and premature death. This is especially true about the outdoor workers like farmers whose involves performing physical task and those experience high Heat stress condition (1, 2). Hence, the present research aimed to evaluate Heat stress exposure among the farmers and also to compare the different Heat stress and strain indices for assessing Heat exposure of the farmers.

Heat stress is well recognized among the hazardous physical agents that might be present during work. This study aims to compare WBGT index at acclimated and unacclimated people to permissible threshold limit value and study the differences between physiological parameters at them. Twenty one healthy men were participated in the study. All of the subjects were monitored in two different weather and working conditions: the Kar site (the work site) and the Paziresh site (the office site). A set of physiological and environmental parameters, namely heart rate, blood pressure, skin temperature and deep body temperature, dry temperature, wet natural temperatures, radiant temperature and relative humidity were measured and monitored simultaneously. The acclimated subjects were all of the ammonia-phase workers working in the hot-humid worksite. Other participants were selected from the work sites without risk of Heat stress. Mean value of WBGT/TLV was less than one for the both acclimated and unacclimated groups at Paziresh site, while this value was more than one at Kar site and also mean of WBGT. For two groups, TWA / TLV were less than one during the working day. Mean physiological parameters were not significantly different between the acclimated and unacclimated subjects at both sites. However, physiological parameters such as heart rate and core body temperature showed statistically significant difference between two groups at Kar. Both groups of Paziresh were not exposed to Heat stress, but Kar's operators continued work under conditions of Heat stress.