Effects Of Heat Stress Research Articles

Potentials of Phyllanthus amarus, Viscum album and Moringa oleifera supplements to mitigate heat stress in female rabbits in humid tropics.

Global warming is a key challenge subjecting animals to heat stress conditions resulting in multiple physiological alterations in tropical climate. Dietary approach seems to be the more friendly approach to curb the adverse effects of heat stress in rabbits. Some herbs have been categorized to have high potential for promotion of immune responses for amelioration of heat stress. Thus, this research aims to evaluate the potential of Mistletoe (Viscum album), Moringa (Moringa oleifera) and Phyllanthus (Phyllanthus amarus) leaf meal as herbal supplements for the alleviation of heat stress in female rabbits by measuring improvement in sex and stress hormonal responses in serum biochemistry. 80 Rabbit does were exposed to 4 dietary groups supplemented with each of Mistletoe, Moringa, Phyllanthus and a control in an 84-day trial at the summit of thermal stress in South west Nigeria. Growth indices were monitored throughout the study, blood samples were compiled at the end of the trial to assess serum biochemistry, stress and sex hormonal responses of the Does using standard protocols. The results revealed that final weight and weight gain of Does fed on Phyllanthus were significantly (p < 0.05) higher (11.46% and 14.25%, respectively) than Does on control. The herbal supplements enhance glucose, protein, albumin and globulin, reduced cholesterol, and creatinine of Does under heat stress conditions. Among the herbal treatment groups, mistletoe, moringa and phyllanthus had 12.42%, 18.39% and 16.90%, respectively, lower corticosterone than control groups which had 39.76ng/ml. Triiodothyronine of Does fed control were significantly (p < 0.05) lower than Does on Moringa oleifera and Phyllanthus amarus supplements. Estradiol and Follicle stimulating hormone of rabbit Does fed on moringa supplement were significantly (p < 0.05) higher than other treatments. In conclusion, the herbal supplements tend to mitigate the detrimental outcome of thermal stress on Does by suppressing stress hormones. Moringa oleifera and Phyllanthus amarus enhanced sex hormones while Phyllanthus amarus confered growth promoting effects on the Does.

Supplementation of lemon juice through drinking water on performance, egg quality, serum biochemical indices and combat heat stress in laying pullets

BACKGROUND: Numerous feed additives, such as probiotics, prebiotics, organic acids, and enzymes, have the potential to optimize weight gain, feed efficiency and maintain the acid-base balance which eventually contributes to improve production performance. The purpose of the current study was to investigate the possible advantages of lemon juice (LJ) on laying performance, egg quality, serum biochemical properties, and layers' ability to recover from heat stress. METHODOLOGY: Ninety-six Hy-Line Brown layers all 29 weeks were randomly assigned to four treatments, each with six replications, and were given a six-hour daily drinking experiment. The birds were provided with 0% (control), 0.5%, 1% and 1.5% LJ respectively for 6 weeks. The temperature, humidity, hen day egg production (HDEP) and egg weight (EW) were recorded. Egg quality indices were measured bi-weekly. An analysis of total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), blood glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), packed cell volume (PCV), heterophil (H), lymphocyte (L) count, and heterophil-lymphocyte (H/L) ratio was performed on the blood sample collected at the end of the experiment. KEY FINDINGS: The studied parameters among the various treated groups showed that the egg weight, feed conversion ratio (FCR), egg quality parameters, HDL, TG, AST, heterophil count, lymphocyte count and H/L ratio did not differ significantly (P &gt; 0.05). HDEP, egg mass output (EMO) and FI differed significantly (P &lt; 0.01) compared to the control group. The significant reduction in TC, LDL, glucose, ALT, increase in feed intake, HDEP and PCV showed that LJ had a positive effect in reducing the adverse effects of heat stress in laying pullets. CONCLUSION: Taken together, it may be concluded that LJ can be used to improve the laying performance and reduce the heat stress in layers.

Dissecting the effect of heat stress on durum wheat under field conditions.

Heat stress negatively affects wheat production in several ways, mainly by reducing growth rate, photosynthetic capacity and reducing spike fertility. Modeling stress response means analyzing simultaneous relationships among traits affecting the whole plant response and determinants of grain yield. The aim of this study was to dissect the diverse impacts of heat stress on key yield traits and to identify the most promising sources of alleles for heat tolerance. We evaluated a diverse durum wheat panel of 183 cultivars and breeding lines from worldwide, for their response to long-term heat stress under field conditions (HS) with respect to non stress conditions (NS), considering phenological traits, grain yield (GY) and its components as a function of the timing of heat stress and climatic covariates. We investigated the relationships among plant and environmental variables by means of a structural equation model (SEM) and Genetic SEM (GSEM). Over two years of experiments at CENEB, CIMMYT, the effects of HS were particularly pronounced for the normalized difference vegetation index, NDVI (-51.3%), kernel weight per spike, KWS (-40.5%), grain filling period, GFP (-38.7%), and GY (-56.6%). Average temperatures around anthesis were negatively correlated with GY, thousand kernel weight TKW and test weight TWT, but also with spike density, a trait determined before heading/anthesis. Under HS, the correlation between the three major determinants of GY, i.e., fertile spike density, spike fertility and kernel size, were of noticeable magnitude. NDVI measured at medium milk-soft dough stage under HS was correlated with both spike fertility and grain weight while under NS it was less predictive of grain weight but still highly correlated with spike fertility. GSEM modeling suggested that the causal model of performance under HS directly involves genetic effects on GY, NDVI, KWS and HD. We identified consistently suitable sources of genetic resistance to heat stress to be used in different durum wheat pre-breeding programs. Among those, Desert Durums and CIMMYT'80 germplasm showed the highest degree of adaptation and capacity to yield under high temperatures and can be considered as a valuable source of alleles for adaptation to breed new HS resilient cultivars.

Effects of vitamin C and early-age thermal conditioning on pituitary adrenocorticotropic hormone cells in broilers chronically exposed to heat stress: an immunohistomorphometric and hormonal study.

The aim of this study was to examine the effects of heat stress (HS) on the pituitary-adrenal axis and whether the treatments with early-age thermal conditioning (ETC) and vitamin C, alone and in combination, could have a beneficial effect in alleviating these effects. For the experiment, 400 one day-old broilers (both sexes) were used, being divided into four groups. The first group was the control (K), the second group (C) consisted of broilers which received vitamin C from the 22nd to the 42nd day via water in the amount of 2.00 g L-1, in the third group (T), broilers were exposed to ETC for a period of 24 hr at a temperature of 38.00 ± 1.00 ˚C and the fourth group (T + C) was the combination of T and C groups. Immunohistochemically positive adrenocorticotropic hormone (ACTH) cells of broilers in all groups were irregular or stellate and distributed in the periphery and central parts of the pituitary gland, as solitary cells or in clusters. In the T + C group of broilers, a significant increase in the area of ACTH cells (18.91%) and their cores (22.75%), and cortisol level in serum compared to the control group was observed. This reaction of broilers in the T + C group facilitated their adaptation to unfavorable consequences of HS. These results suggest that hypothalamic-pituitary-adrenal axis is stimulated after the exposure to chronic HS, enabling successful adaptation of broilers to adverse conditions.

The effect of protein and selenium on broiler performance and blood parameters in summer conditions

Heat stress presents a substantial challenge for the poultry industry, negatively impacting broilers' health, growth, and productivity. Optimizing dietary crude protein (CP) levels is a viable approach to reduce the heat generated during birds' amino acid oxidation process. Additionally, supplementing diets with Selenium (Se), a potent antioxidant, can help counteract the detrimental effects of heat stress on broiler growth performance. To explore the effects of varying CP and Se levels on growth performance, carcass characteristics, blood parameters, immune function, and blood leukocyte profiles in broiler chickens under heat stress, a 42-day experiment was conducted. It involved 528 male broiler chicks (Ross 308), divided into six groups with 11 chicks each, fed diets with 100%, 94%, or 88% of the recommended CP levels, and two Se levels (0 and 0.04 mg/kg). The findings indicated that reducing dietary CP levels led to an improvement in daily weight gain (DWG) without affecting feed intake (FI), feed conversion ratio (FCR), or carcass traits. There was a significant interaction between CP and Se levels regarding glucose, albumin, uric acid, cholesterol, triglyceride levels, antibody titers against Newcastle disease virus (NDV), and monocyte counts. Se supplementation increased NDV antibody titers at 14 days, whereas reducing CP lowered these titers at 21 days. The study concluded that lowering dietary CP did not adversely affect growth performance, carcass quality, or blood parameters; it even enhanced DWG compared to a normal protein diet and influenced some blood parameters.

Community Adaptation to Heat stress − Social Network Analysis

Rising climate disasters underscore the overlooked impact of heat stress on health and productivity in densely populated Southeast Asia, particularly vulnerable coastal areas like India's. This study in the Indian Sundarbans employs surveys and social network analysis to explore heat stress effects, community adaptation, and support networks. Recognizing community significance, it views resilience as a blend of agency, wisdom, and networks. The research unveils rural adaptive behaviours, co-occurring stress responses, and network use for health solutions. These insights aim to enhance health advisories and crisis responses, fostering resilience in communities facing escalating climate challenges. The research covered 747 households from nine village segments, examining heat stress adaptation and social support networks. Social Network Analysis revealed internal and external sources of support for heat stress-induced health issues. The study employed matrices and network analysis tools to represent co-occurrence patterns of adaptation strategies and support networks. Findings highlighted collective adaptive behaviour and the role of social connections in combating climatic stress. The study outlines dual interventions to mitigate heat stress impacts: enhancing endogenous community adaptability and optimizing social-institutional networks for external support. Occupational profiling, socio-economic context, and health access can identify vulnerable groups. Perceived impacts can serve as early health crisis indicators, though not always linked to adaptive actions. Diverse adaptive activities co-occur, reflecting collective behaviour, but less central actions require attention. Medical care usage for heat stress remains minimal. Social networks lack local health providers needing community-level provisions. A comprehensive mitigation plan for identified vulnerable communities aims to bridge knowledge gaps, promote equitable healthcare access, and strengthen adaptive capacity through informed interventions.

Effect of heat stress on meat quality: A review

One of the stressful situations for livestock and poultry is heat stress (HS), which has a detrimental effect on animal physiology, production, and product quality. Because of their quick development and metabolism, high production, and species-specific characteristics including decreased sweating, the protective layer of skin, and rumen fermentation, some varieties of livestock are more vulnerable to heat stress than others. Muscle that is pale, soft and exudative (PSE) and lacks the ability to retain water can be produced by short-term heat stress that occurs pre-slaughter. This stress increases muscle glycogenolysis. In contrast, animals that experience prolonged heat stress have lower muscle glycogen reserves, which results in meat that is dark, firm, and dry (DFD), has a high final pH and water retention capacity. Moreover, HS causes shortened shelf life, oxidative stress. According to a recent study, HS might plausibly modify the rate and amount of postmortem muscle glycolysis and the resulting pH, which can impact the physiological and metabolic disturbances that occur in live animals as well as the features of carcasses and meat quality. This review reflects the effect of heat stress on meat quality.

The Immuno-Suppressive Effects of Cyclic, Environmental Heat Stress in Broiler Chickens: Local and Systemic Inflammatory Responses to an Intradermal Injection of Lipopolysaccharide.

To assess effects of environmental heat stress (HS) on the local and systemic inflammatory responses to lipopolysaccharide (LPS), broilers were reared under thermoneutral (TN) or cyclic HS conditions. Thermoneutral temperatures followed commercial production settings, with HS broilers exposed to 35 °C for 14 h/day from 4 days onward. At 37 days, HS- and TN-broilers were assigned to either LPS (100 μg/mL) or endotoxin-free phosphate-buffered saline (PBS; vehicle) treatments, eight each to HS- and TN-LPS, four each to HS- and TN-PBS. Treatments were administered by intradermal injection of growing feather (GF) pulps; 10 μL/GF; 12 GF/broiler. Blood and GF were collected before and at 6 and 24 h post-injection to assess leukocyte population changes in GF-pulps and blood, reactive oxygen species (ROS) generation and cytokine expression in GF-pulps, and plasma concentrations of alpha-1 acid glycoprotein (AGP-1). HS-LPS broilers had lower (p ≤ 0.05) infiltration of heterophils and macrophages, ROS generation, and inflammatory cytokine expression in GF-pulps, and lacked the increases in heterophil, monocyte, and plasma AGP-1 concentrations observed in TN-LPS broilers. HS-broilers had similar or greater drops in blood lymphocytes 6 h post-LPS or -PBS injection, respectively, and lower baseline levels (p ≤ 0.05) of circulating T- and B-lymphocytes than TN-broilers. Results indicated that cyclic HS reduced the local and systemic acute inflammatory responses to LPS in broilers, likely impairing their innate defense against microbial infection.

Combined Effects of Cyclic Heat Stress, Dietary Induced Oxidative Stress and Different Levels of Antioxidant on Gut Fermentation Activity and Mucosal Morphology in Broiler Chickens

The gastrointestinal tract of broilers is susceptible to oxidative stress induced by heat stress (HS) and diet, which can be mitigated by the supply of exogenous vitamins and antioxidants. The aim of this study was to compare the extent of the effects of cyclic HS, and high levels of polyunsaturated fatty acids (PUFA) (HP) on gut health. It also aimed to investigate whether additional supplementation with vitamins E, C and selenium (HA) is required to support gut health under these conditions. In the present study, 192 one-day-old male Ross 308 broilers were randomly divided into eight experimental groups. Exposure to HS and HP significantly (p &lt; 0.001) decreased villus height and villus-to-crypt ratio in the duodenum, while no differences were observed in the jejunum and ileum. In addition, oxidative stress in the liver, indicated by increased malondialdehyde (MDA) levels, was increased in the HP groups (p &lt; 0.0001), while the HA groups had a positive effect on lowering MDA levels. The results confirm that cyclic HS and HP induce oxidative stress that damages the structure of intestinal morphology and that supplementation with HA could be a potential approach to mitigate the negative effects of these stressors.

Strategies to combat heat stress in poultry production-A review.

The effects of heat stress (HS) caused by high temperatures continue to be a global concern in poultry production. Poultry birds are homoeothermic, however, modern-day chickens are highly susceptible to HSdue to their inefficiency in dissipating heat from their body due to the lack of sweat glands. During HS, the heat load is higher than the chickens'ability to regulate it. This can disturb normal physiological functioning, affect metabolismand cause behavioural changes, respiratory alkalosis and immune dysregulation in birds. These adverse effects cause gut dysbiosis and, therefore, reduce nutrient absorption and energy metabolism. Thisconsequentlyreduces production performances and causes economic losses. Several strategies have been explored to combat the effects of HS. These include environmentally controlled houses, provision of clean cold water, low stocking density, supplementation of appropriate feed additives, dual and restricted feeding regimes, early heat conditioningand genetic selection of poultry lines to produce heat-resistant birds. Despite all these efforts, HS still remains a challenge in the poultry sector. Therefore, there is a need to explore effective strategies to address this long-lasting problem. The most recent strategy to ameliorate HS in poultry is early perinatal programming using the in ovo technology. Such an approach seems particularly justified in broilers because chick embryo development (21 days) equals half of the chickens'posthatch lifespan (42 days). As such, this strategy is expected to be more efficient and cost-effective to mitigate the effects of HS on poultry and improve the performance and health of birds. Therefore, this review discusses the impact of HS on poultry, the advantages and limitations of the different strategies. Finally recommend a promising strategy that could be efficient in ameliorating the adverse effects of HS in poultry.

Excess Mortality Risk Due to Heat Stress in Different Climatic Zones of India.

India is at a high risk of heat stress-induced health impacts and economic losses owing to its tropical climate, high population density, and inadequate adaptive planning. The health impacts of heat stress across climate zones in India have not been adequately explored. Here, we examine and report the vulnerability to heat stress in India using 42 years (1979-2020) of meteorological data from ERA-5 and developed climate-zone-specific percentile-based human comfort class thresholds. We found that the heat stress is usually 1-4 °C higher on heatwave (HW) days than on nonheatwave (NHW) days. However, the stress on NHW days remains considerable and cannot be neglected. We then showed the association of a newly formulated India heat index (IHI) with daily all-cause mortality in three cities - Delhi (semiarid), Varanasi (humid subtropical), and Chennai (tropical wet and dry), using a semiparametric quasi-Poisson regression model, adjusted for nonlinear confounding effects of time and PM2.5. The all-cause mortality risk was enhanced by 8.1% (95% confidence interval, CI: 6.0-10.3), 5.9% (4.6-7.2), and 8.0% (1.7-14.2) during "sweltering" days in Varanasi, Delhi, and Chennai, respectively, relative to "comfortable" days. Across four age groups, the impact was more severe in Varanasi (ranging from a 3.2 to 7.5% increase in mortality risk for a unit rise in IHI) than in Delhi (2.6-4.2% higher risk) and Chennai (0.9-5.7% higher risk). We observed a 3-6 days lag effect of heat stress on mortality in these cities. Our results reveal heterogeneity in heat stress impact across diverse climate zones in India and call for developing an early warning system keeping in mind these regional variations.

Rye-grass-derived probiotics alleviate heat stress effects on broiler growth, health, and gut microbiota

The primary aim of this study was to assess the impact of liquid (S-LAB) and lyophilized (L-LAB) probiotics sourced from Rye-Grass Lactic Acid Bacteria on broilers experiencing heat stress. The study involved 240 broiler chicks divided into six groups. These groups included a negative control (Control) with broilers raised at a normal temperature (24 °C) on a basal diet, and positive control groups (S-LAB and L-LAB) with broilers under normal temperature receiving a lactic acid bacteria supplement (0.5 mL/L) from rye-grass in their drinking water. The heat stress group (HS) comprised broilers exposed to cyclic heat stress (5–7 h per day at 34–36 °C) on a basal diet, while the heat stress and probiotic groups (S-LAB/HS and L-LAB/HS) consisted of broilers under heat stress supplemented with the rye-grass-derived lactic acid bacteria. Results indicated that heat stress without supplementation (HS) led to reduced body weight gain, T3 levels, citrulline, and growth hormone levels, along with an increased feed conversion ratio, serum corticosterone, HSP70, ALT, AST, and leptin levels. Heat stress also negatively impacted cecal microbiota, decreasing lactic acid bacteria (LABC) while increasing E. coli and coliform bacteria (CBC) counts. Probiotic supplements (S-LAB/HS and L-LAB/HS) mitigated these effects by enhancing broilers' resilience to heat stress. In conclusion, rye grass-derived S-LAB and L-LAB probiotics can effectively support broiler chickens under heat stress, promoting growth, liver function, hormonal balance, gut health, and cecal microbiome ecology. These benefits are likely mediated through improved gut health.

Effect of heat stress on growth performance, carcase characteristics, meat quality and rumen-muscle axis of Hu sheep

This study aimed to investigate the effects of heat stress (HS) on growth performance, carcase characteristics and rumen-muscle axis of Hu sheep and to explore the underlying molecular mechanisms of the actions by establishing a heat-stressed Hu sheep. The results showed that HS significantly decreased growth performance and carcase characteristics, altered metabolic enzyme activities, and induced a shift in muscle energy metabolism towards a more glycolytic and less oxidative fibre type in the longissimus dorsi (LD) muscle (p < 0.05), thereby affecting the meat quality of Hu sheep. Furthermore, RNA-seq analysis of LD muscle found that HS down-regulated the expression of genes (ADIPOQ, ADRA2A, COL6A3, MYOC, PPARGC1A, etc.) involved in fat deposition and muscle development. 16S rDNA analyses of ruminal microbiome revealed that resist adverse environments-related Firmicutes, fatty acid synthesis-related Ruminococcaceae, Prevotellaceae, etc. were increased in the heat-stressed Hu sheep, and negatively correlated with genes involved in muscle development and lipid metabolism. However, energy metabolism-related Bacteroidetes and Tenericutes, and protein and carbohydrate cleavage-related Prevotella and Mollicutes were decreased in the heat-stressed Hu sheep and positively correlated with genes involved in muscle development and lipid metabolism. All together, these findings indicated that the rumen microbiota and gene expression profiles of muscle underwent responsive changes to HS, which impaired growth performance, carcase characteristics and meat quality in Hu sheep. Our findings provide valuable insights into the mechanisms underlying heat stress-induced effects in sheep, suggesting potential strategies for the prevention and control of HS as well as the development of new heat-resistant varieties in Hu sheep using molecular design breeding.

Phenotypic, Physiological and Biochemical Delineation of Wheat Genotypes Under Different Stress Conditions.

Wheat is a vital crop, providing calories, nutrients and versatility in the food industry. However, the combination of heat and drought stress, exacerbated by climate change, poses a significant threat to wheat production, leading to potential yield losses. To ensure the sustainability of wheat production it is crucial to prioritize research on developing stress-tolerant wheat genotypes. The current study focused on identifying the traits that are important for developing stress-tolerant wheat varieties under timely sown irrigated, drought stress, heat stress, and combined stress conditions. It addresses the knowledge gap regarding the combined effects of heat and drought stress on wheat physiology and yield, aiming to shed light on the intricate interactions between these stresses. The experiment was conducted at CCS HAU, Hisar, during the Rabi seasons of 2019-2020 and 2020-2021. By evaluating variability parameters, conducting correlation analysis, and path coefficient analysis among 80 diverse wheat genotypes, this research identifies genetic factors contributing to stress tolerance and helps select plants with desirable characteristics. The results showed that traits i.e., malendialdehyde, wax covering on blade, wax covering on sheath and wax covering on spike had high potential for improvement through selection among genotypes for grain yield and its component traits. The study also highlighted the importance of selecting wheat varieties with early maturity to mitigate the risk of yield loss under combined stress conditions. Moreover, the interaction between drought and heat stress can increase oxidative stress, leading to elevated malondialdehyde levels. Selecting varieties with lower malondialdehyde and optimal canopy temperature is important. Understanding the complex response of wheat to heat, drought, and their combined stress is essential for improving crop quality and production potential. Overall, this research contributes to the field of plant breeding by facilitating the development of wheat varieties with high and stable yields in challenging environments.

Effects of heat stress on feed intake, milk yield, milk composition, and feed efficiency in dairy cows: A meta-analysis

Heat stress compromises dairy production by decreasing feed intake and milk yield, and it may also alter milk composition and feed efficiency. However, little information is available for evaluating such effects across different levels of heat stress and cows enrolled in heat stress studies. The objectives of this study were to evaluate the effects of heat stress on dry matter intake (DMI), energy-corrected milk (ECM), milk composition, and feed efficiency (kg ECM/kg DMI) and to investigate the relationship between such effects and heat stress intervention and animal characteristics by using meta-analytical approaches. Data from 31 studies (34 trials) fulfilled the inclusion criteria and were used for analysis. Results showed that heat stress decreased DMI, ECM, and milk protein concentration, but did not alter milk fat concentration or feed efficiency. Meta-regression confirmed that such reductions in DMI and ECM were significantly associated with increasing temperature-humidity index (THI). Over the period of heat stress, for each unit increase in THI, DMI and ECM decreased by 4.13% and 3.25%, respectively, in mid-lactation cows. Regression models further revealed the existence of a strong interaction between THI and lactation stage, which partially explained the large heterogeneity in effect sizes of DMI and ECM. The results indicated a need for more research on the relationship between the effect of heat stress and animal characteristics. This study calls for the implementation of mitigation strategies in heat-stressed herds due to the substantial decrease in productivity.

Preliminary characterization of biomolecular processes related to plasticity in Acyrthosiphon pisum

Global warming strongly impacts many organisms' development, distribution and population structure. This problem has attracted the attention of many scientists to understand and study its actual effects, especially on insects influenced by environmental temperatures. Aphids are a model for studies of the genetics and physiology of stress. Aphids are characterized by parthenogenetic reproduction, which limits the effects of recombination on evolutionary processes, and have shown resistance to various biotic and abiotic stresses. This study was based on the hypothesis that aphids have optimized, over time, genetic mechanisms capable to give them plasticity through genome modifications mediated by transposition. To understand and evaluate the effects of heat stress, the expression levels of transposases and methylases were analyzed in mothers and daughters. Our results show that after four days from the thermal shock, methylation decreases in both mothers and daughters, while transposition significantly increases in daughters, thus generating gene variability, essential for adaptation.

How Does the Provision of Shade during Grazing Affect Heat Stress Experienced by Dairy Cows in Sweden?

Heat stress in dairy cows can cause an increase in body temperature and respiration rate, and a decreased feed intake leading to reduced production. Dairy cows are better at handling heat when they have access to shade. Therefore, this study aimed to determine the effects of providing shade to high-yielding dairy cattle during the summer in the Swedish climate. Twenty high-yielding Swedish Red dairy cows, held on pasture, were divided into two groups, one with access to shade (S) and one without (NS). Milk production was recorded daily and shade temperature and relative humidity were recorded at 10 min intervals at pasture. A major effect of heat stress was found in cows in early lactation in the NS group. In this group, a high mean temperature two days before and a high THI two days before affected the milk production negatively (p < 0.001), which was the same for the maximum temperature and maximum THI measured on the same day (p < 0.001). Increases in the mean temperature and THI two days before also affected milk production negatively (p < 0.05) for cows in early lactation in the S group, though to a lesser extent. This study suggests that dairy cows in early lactation benefit from access to shade during summer.

The Effects of Heat Stress on Bakery Workers: A Systematic Review.

Working in hot environments can cause diseases and reduce performance by upsetting the balance of physiological parameters of workers' bodies. Bakers are among the people exposed to heat stress continuously and daily. This review study aimed to investigate the effect of heat stress on bakers. In this review study, the related articles based on keywords were reviewed using "IranMedex", "Science Direct", "PubMed", "Scopus", "Web of Science", "SID", "Google Scholar", and "Magiran" databases from the years 2000 to 2021. The used search terms were "Heat stress", "Heat strain", "Heat exposure", "Heat waves", "Workplace", "Baker", and "health effects". In order to extract the required data, all parts of the articles have been reviewed. Out of the 16 studies reviewed in this study, 43.75% were cross-sectional, 25% were descriptive cross-sectional, and 31.25% were performed according to other study designs. In all of the studies, the WBGT index was used to assess ambient heat stress. In most studies, the mean exposure temperature was higher than the WBGT-ACGIH limit, especially among traditional bakery workers. The findings showed that exposure to thermal stress significantly affects some hematological parameters of blood, oxidative stress, heart rate, and body temperature. The situation of heat stress in the bakery environment is worrying in terms of health and reduced productivity of employees. Therefore, it is essential to take the necessary preventive and control measures to reduce heat stress and the resulting strain.

196 Sustainable effect of heat stress during maturation on the bioenergetics profile of bovine blastocysts

196 Sustainable effect of heat stress during maturation on the bioenergetics profile of bovine blastocysts

The impact of heat stress in plant reproduction.

The increment in global temperature reduces crop productivity, which in turn threatens food security. Currently, most of our food supply is produced by plants and the human population is estimated to reach 9 billion by 2050. Gaining insights into how plants navigate heat stress in their reproductive phase is essential for effectively overseeing the future of agricultural productivity. The reproductive success of numerous plant species can be jeopardized by just one exceptionally hot day. While the effects of heat stress on seedlings germination and root development have been extensively investigated, studies on reproduction are limited. The intricate processes of gamete development and fertilization unfold within a brief timeframe, largely concealed within the flower. Nonetheless, heat stress is known to have important effects on reproduction. Considering that heat stress typically affects both male and female reproductive structures concurrently, it remains crucial to identify cultivars with thermotolerance. In such cultivars, ovules and pollen can successfully undergo development despite the challenges posed by heat stress, enabling the completion of the fertilization process and resulting in a robust seed yield. Hereby, we review the current understanding of the molecular mechanisms underlying plant resistance to abiotic heat stress, focusing on the reproductive process in the model systems of Arabidopsis and Oryza sativa.