Environmental Heat Stress Research Articles

093 Ovarian follicle extracellular vesicle-microRNAs mediated response of beef cows to environmental heat stress

093 Ovarian follicle extracellular vesicle-microRNAs mediated response of beef cows to environmental heat stress

Predicting the body core temperature of recreational athletes at the end of a 10 km self-paced run under environmental heat stress.

What is the central question of this study? The aim was to identify the factors predicting the body core temperature of athletes at the end of a 10km self-paced run in a hot environment. What is the main finding and its importance? Hyperthermia in athletes subjected to self-paced running depends on several factors, highlighting the integrated control of core temperature during exercise under environmental heat stress. Five of the seven variables that significantly predicted core temperature are not invasive and, therefore, practical for use outside the laboratory environment: heart rate, sweat rate, wet-bulb globe temperature, running speed and maximal oxygen consumption. Measurement of body core temperature (Tcore ) is paramount to determining the thermoregulatory strain of athletes. However, standard measurement procedures of Tcore are not practical for extended use outside the laboratory environment. Therefore, determining the factors that predict Tcore during a self-paced run is crucial for creating more effective strategies to minimize the heat-induced impairment of endurance performance and reduce the occurrence of exertional heatstroke. The aim of this study was to identify the factors predicting Tcore values attained at the end of a 10km time trial (end-Tcore ) under environmental heat stress. Initially, we extracted data obtained from 75 recordings of recreationally trained men and women. Next, we ran hierarchical multiple linear regression analyses to understand the predictive power of the following variables: wet-bulb globe temperature, average running speed, initial Tcore , body mass, differences between Tcore and skin temperature (Tskin ), sweat rate, maximal oxygen uptake, heart rate and change in body mass. Our data indicated that Tcore increased continuously during exercise, attaining 39.6±0.5°C (mean±SD) after 53.9±7.5min of treadmill running. This end-Tcore value was primarily predicted by heart rate, sweat rate, differences between Tcore and Tskin , wet-bulb globe temperature, initial Tcore , running speed and maximal oxygen uptake, in this order of importance (β power values corresponded to 0.462, -0.395, 0.393, 0.327, 0.277, 0.244 and 0.228, respectively). In conclusion, several factors predict Tcore in athletes subjected to self-paced running under environmental heat stress. Moreover, considering the conditions investigated, heart rate and sweat rate, two practical (non-invasive) variables, have the highest predictive power.

Impact of environmental heat exposure on the health status in farmworkers, Nakhon Ratchasima, Thailand.

Thailand is a tropical developing country which has a serious increase in health risk due to hot weather exposure among outdoor workers. The aims of this study were to compare the factors related to environmental heat exposure in three different seasons, and to assess the relationship between environmental heat and dehydration status in each season among farmworkers in Nakhon Ratchasima, Thailand. A semi-longitudinal study was carried out in 22 male farmworkers throughout a year of farming. The primary data were collected in farmworkers for socio-demographic information, clinical assessments, and heat-related illnesses. Average of environmental heat index (Median, SD) were severe in summer (WBGT=38.1, 2.8°C), rainy season (WBGT=36.1, 2.1°C), and winter (WBGT=31.5, 2.7°C). Average urine Sp. Gr. in summer, rainy season, and winter were 1.022, 1.020, and 1.018 respectively. The third sentence should be corrected as follows: The Friedman analysis revealed a statistically significant difference between the three different seasons in WBGT (wet bulb globe temperature), body temperature, heart rate (P<0.01), and respiratory rate (P<0.05). There was a statistically significant difference between the three different seasons for skin rash/itching, dizziness, muscle cramp dyspnea (P<0.05), and weakness (P<0.01). Wilcoxon signed-ranks analysis found a significant difference in the medians of the paired sets of urine Sp. Gr. values between baseline and summer (P<0.05). Spearman's rank correlation coefficient did not find a relationship between WBGT and urine Sp. Gr. in the three different seasons. This study demonstrated that farmworkers had exposure to environmental heat stress which was expressed through physical changes. Therefore, there is a need for either interventions or guidelines to prevent dehydration for outdoor workers in this region.

Microsclerotial pellets of Metarhizium spp.: thermotolerance and bioefficacy against the cattle tick

The cattle tick, Rhipicephalus microplus (Acari: Ixodidae), is a multi-billion dollar ectoparasite of global importance affecting beef and milk production. Submerged cultures of cosmopolitan entomopathogenic fungal species of the genus Metarhizium typically produce microsclerotia that provide both long-term survival and environmental resistance. Microsclerotia hold great potential as an unconventional active propagule to control this tick under laboratory and semi-field conditions. However, heat stress caused especially by elevated temperatures poses a critical environmental constraint for the successful development and efficacy of microsclerotia under tropical conditions. First, we screened six strains of Metarhizium anisopliae, Metarhizium robertsii and Metarhizium humberi for their ability to produce microsclerotia by submerged liquid cultivation. In addition, we assessed the biological fitness and bioefficacy of dried microsclerotial pellets under amenable (27°C) and heat-stressed (32°C) incubation against engorged adult females of R. microplus. Microsclerotia in pelletized formulation prepared with carriers based on diatomaceous earth and microcrystalline cellulose exhibited conidial production at different extents according to the fungal strain and the incubation temperature, but most strains displayed reduced sporogenesis when exposed to 32°C. Engorged tick females exposed to sporulated microsclerotia from pelletized M. anisopliae CG47 or IP 119 had fewer number of hatching larvae in comparison to the control group, irrespective of the incubation temperature tested. The minimum dosage of microsclerotial pellets that effectively reduced hatchability of tick larvae was estimated to be 2mg per plate (equivalent to 6.0kg per hectare). Metarhizium microsclerotial pellets exhibited significant tolerance to 32°C and pronounced acaricidal activity against this economically important ectoparasite of cattle, even under simulated environmental heat stress. KEY POINTS: • Heat stress affects conidial production by microsclerotia of most pelletized Metarhizium strains • Heat stress does not impair the acaricidal performance of pelletized microsclerotia • Pellet formulation of Metarhizium microsclerotia is a promising mycoacaricide.

Carbohydrate mouth rinse is no more effective than placebo on running endurance of dehydrated and heat acclimated athletes.

To determine whether carbohydrate mouth rinsing would improve endurance running performance of tropical natives in a warm-humid (30°C and 70% relative humidity) environment. Twelve endurance male runners [age 25 ± 3 years; peak aerobic capacity ([Formula: see text]O2peak) 57.6 ± 3.6mL.kg-1.min-1] completed three time-to-exhaustion (TTE) trials at ~ 70% [Formula: see text]O2peak while swilling 25ml of a 6% carbohydrate (CHO) or taste-matched placebo (PLA) as well as no mouth rinse performed in the control (CON) trial. TTE performance was significantly longer in both CHO and PLA trials when compared with the CON trial (54.7 ± 5.4 and 53.6 ± 5.1 vs. 48.4 ± 3.6min, respectively; p < 0.001 and p = 0.012, respectively), but was not significantly different between CHO and PLA trials (p = 1.000). The rating of perceived exertion was not different between the CHO and PLA trials, however, was significantly affected when compared to the CON trial (p < 0.001). A similar effect was observed for perceived arousal level between the CHO and PLA trials to the CON trial. Core temperature, mean skin temperature and skin blood flow were not significantly different between the three trials (all p > 0.05). Similarly, plasma lactate and glucose as well as exercise heart rate were not influenced by the trials. The present study demonstrates that mouth rinsing, whether carbohydrate or placebo, provides an ergogenic benefit to running endurance when compared to CON in a heat stress environment. Nevertheless, the results do not support the notion that rinsing a carbohydrate solution provides a greater advantage as previously described among non-heat acclimated individuals within a temperate condition.

Genetic Improvement for Grain Yield under Heat Stress Conditions in Bread Wheat (Triticum aestivum L.)

Extreme temperature is one of the abiotic stresses that causes significant yield reductions in wheat. Therefore, the current study aims to create heat-tolerant wheat plants with superior grain yield productivity by using traditional breeding. Two cycles of phenotypic directional selection for grain yield per plant were applied in two F2 populations. These populations were derived from crosses among four local wheat varieties. In the first cycle, a directional selection for grain yield per plant was performed under both the favorable environment (optimal sowing date) and heat stress environments (late sowing date). Under the favorable conditions, the responses of F3 plants to selection for grain yield per plant were positive and significantly higher (averaged 7.71%) than under heat stress conditions (averaged 8.20%). Moreover, the average of the concurrent response to selection for grain yield per plant in grain yield per spike had a positive and high percentage under the favorable (7.00%) and the heat stress environment (8.84%). Highly significant and positive responses were observed within the F3 plants of the two populations. The value of the average was greater under favorable (6.85%) than under the heat stress conditions (7.20%). Additionally, the 1000 kernel weight was highly significant and positive responses (5.35% and 6.11%) in both favorable and heat stress environments, respectively. Generally, the observed results indicating the F4 plants could be a promising source to introduce yield related traits to develop high-yielding wheat cultivars for heat-stressed environments.

고온 환경에서 카테킨 및 비타민 C 첨가가 육계의 생산성, 계육품질, 혈액성분 및 스트레스 지표에 미치는 영향

The study was carried out to investigate the effects of dietary combined supplementation of antioxidants as catechin and vitamin C on growth performance, meat quality, blood profiles and stress responses of broilers exposed to high temperature. For this experiment, a total of 360 21-day-old male Ross 308 broilers were used. Treatments were assigned with 6 replicates per treatment and 10 birds per replicate in a 2 × 3 factorial design with vitamin C (0, 250 mg/kg) and catechin (0, 600, 1,200 mg/kg). The heat stress environment was maintained at temperature 32±1°C and relative humidity 60±5% for 24 hours until the end of the experiment. The supplemented antioxidants had no significant difference in weight gain, feed intake and feed conversion ratio (<i>P</i>&gt;0.05). The content of total cholesterol in blood had no interaction, but decrease (<i>P</i>&lt;0.01) in the supplemented catechin group. Also, the supplementation with catechin showed increase in the SOD activity of blood, and lower corticosterone and IgM levels of broilers. The contents of HSP70 and MDA in liver decrease (<i>P</i>&lt;0.05) with the supplementation of antioxidants, and HSP70 showed an interaction between groups. DPPH radical scavenging ability in breast meat increased (<i>P</i>&lt;0.01) in catechin, but meat quality did not show difference according to treatments. Respiratory rate decreased (<i>P</i>&lt;0.05) in catechin, but no interaction with vitamin C. In conclusion, the combination of vitamin C and catechin can alleviate stress under high temperature, such as HSP70 and MDA, but further study on the optimal supplemental level is needed.

Thermal strain is greater in the late afternoon than morning during exercise in the gym without airflow and air conditioning on a clear summer day.

There are no reports examining the time-of-day effect on team training sessions in the gym without airflow and air conditioning on thermal strain in the summer heat. We investigated this effect during badminton training sessions on a clear summer day. Nine male high school badminton players (Mean ± SD; age 17.1 ± 0.6 y, height 171 ± 4 cm, body mass 59 ± 7 kg) completed two 2.5-h badminton training sessions in the gym without airflow and air conditioning. The training sessions were started at 0900 h (AM) and 1600 h (PM) on separate days in August. Skin temperatures (chest, triceps, thigh, calf), infrared tympanic temperature, heart rate, thermal sensation and rating of perceived exertion were recorded at rest and at regular intervals during the sessions. Indoor and outdoor environmental heat stress progressively increased in AM and decreased in PM during the sessions. Ambient temperature (AM 30.1 ± 0.9°C; PM 33.2 ± 1.0°C: P < 0.001) and wet-bulb globe temperature (AM 28.1 ± 0.5°C; PM 30.0 ± 0.9°C: P = 0.001) during the sessions in the gym were higher in PM than AM. Mean skin temperature (AM 34.2 ± 1.0°C; PM 34.7 ± 0.7°C: P < 0.001), infrared tympanic temperature (AM 37.8 ± 0.5°C; PM 38.1 ± 0.4°C: P = 0.001) and thermal sensation (AM 2.7 ± 1.4; PM 3.3 ± 1.0: P < 0.001) during the sessions were higher in PM than AM. Body heat storage (AM 159 ± 30 W·m-2; PM 193 ± 30 W·m-2: P < 0.05) was greater in PM than AM. There were no time-of-day differences in the average heart rate (AM 75 ± 4% age-predicted maximal heart rate; PM 76 ± 5 age-predicted maximal heart rate: P = 0.534), body mass loss (AM 0.6 ± 0.3 kg; PM 0.8 ± 0.2°C: P = 0.079), the volume of water ingested (AM 1.5 ± 0.1 L; PM 1.6 ± 0.3 L: P = 0.447) and rating of perceived exertion (AM 16 ± 2; PM 16 ± 3: P = 0.281). This study indicates greater thermal strain in PM trial than in AM trial during team training sessions in the gym without airflow and air conditioning on a clear summer day. Therefore, athletes and coaches of indoor sports should perceive that athletes may be exposed to a greater risk for thermal strain in the late afternoon from 1600 h than in the morning from 0900 h during the sessions in the gym under these conditions.

Two decades of nighttime surface urban heat island intensity analysis over nine major populated cities of India and implications for heat stress

Warmer global climate and urban heat islands (UHIs) interact, by exacerbating heatwaves and increasing the extreme heat days in cities. The implications of added heat stress in urban environments due to intensifying surface UHIs (SUHIs) is of utmost concern. Seasonal, annual and decadal nighttime SUHI intensities (SUHIIs), from 2001 to 2020, for nine major populated cities of India are analyzed. This includes five megacities- Delhi, Mumbai, Kolkata, Bangalore, and Chennai, and four incipient megacities- Hyderabad, Ahmedabad, Surat, and Pune. The key role of increasing urbanization (pre- and post-2010) in expansion and intensification of nighttime SUHIs in India is highlighted. For all cities either pre-monsoon (MAM) or winter (December-February; DJF) seasons show the strongest SUHII development. During the 2001–2010, and the 2011–2020 decade, a nighttime SUHII maxima of respectively (i) 2.1°C and 2.5°C for Delhi, (ii) 1.3°C and 1.5°C for Mumbai, (iii) 1.3°C and 1.5°C for Kolkata, (iv) 0.6°C and 1.0°C Bangalore, (v) 1.7°C and 1.9°C for Chennai, (vi) 1.8°C and 2.3°C for Hyderabad, (vii) 2.8°C and 3.1°C for Ahmedabad, (viii) 1.9°C and 2.4°C for Surat, and (ix) 0.8°C and 1.3°C for Pune is noted. Further, all incipient megacities showed a mean annual growth rate of nighttime SUHII of over 0.007°C/year, substantially greater than in the megacities. High SUHII magnitudes, greater growth rates of SUHII, and huge populations, severely compounds the vulnerability of Indian cities to excessive heat exposure risk, especially during MAM heatwaves. Lastly, the implications of nighttime SUHII findings from the present study, on the increase in heat stress, the loss of labor productivity and the rise in heat-related mortality rate is emphasized. The study recommends implementation of city-specific action plans to mitigate the heat stressed urban environment. Targeted use of cooling strategies in localized hotspots within the urban areas where high intensity SUHIs are likely to form is also suggested.

Limitations associated with thermoregulation and cardiovascular research assessing laborers performing work in the heat.

To quantify the current literature and limitations associated with research examining thermoregulatory and cardiovascular strain in laborers working in the heat. PubMed, SCOPUS, and SPORTDiscus were searched for terms related to the cardiovascular system, heat stress, and physical work. Qualifying studies included adult participants (18-65 years old), a labor-intensive environment or exercise protocol simulating a labor environment, a minimum duration of 120 min of physical work, and environmental heat stress (ambient temperature ≥26.0°C and ≥30% relative humidity). Studies included at least one of the following outcomes: pre- and peakphysical work, core temperature, heart rate (HR), systolic blood pressure, diastolic blood pressure, HR variability, and rate pressure product. Twenty-one out of 1559 potential studies qualified from our search. There was a total of 598 participants (mean = 28 ± 50 participants per study, range = 4-238 participants per study), which included 51 females (8.5%) and 547 males (91.5%). Of the participants, 3.8% had cardiovascular risk factors (diabetes: n = 10; hypertension: n = 13)and 96.2% were characterized as "healthy". Fifty-seven percentof the included studies were performed in a laboratory setting. Studies were predominantly in men (91.5%), laboratory settings (57%), and "healthy" individuals (96.2%). To advance equity in protection against occupational heat stress and better inform future heat safety recommendations to protect all workers, future studies must focus on addressing these limitations. Employers, supervisors, and other safety stakeholders should consider these limitations while implementing current heat safety recommendations.

L-serine modulates activities of antioxidant enzymes and behavioral responses in broiler chickens subjected to feed restriction during the hot-dry season

The aim of the study was to evaluate the effects of L-serine on catalase and glutathione peroxidase activities; latency, rest, number of lines crossed, attempts at jumping, vocalization, defecation, preening rate and tonic immobility of broiler chickens subjected to feed restriction during the hot-dry season. Broiler chicks (n =120) were divided into four groups of 30 each: Group A: feed restriction (FR); Group B: feed restriction + L-serine (FR + L-serine); Group C: feed ad libitum (AL); and Group D: feed ad libitum + L-serine (FR + L-serine). L-serine (200 mg/kg) was administered for 14 days orally from one-day old. Broiler chickens were subjected to 20%-feed restriction from day 7-14 of rearing. The temperature-humidity index recorded from the study period was 30.88 ± 0.81, indicating the chickens were subjected to environmental heat stress. At weeks 3, 4 and 5, serum catalase and glutathione peroxidase activities were evaluated. Tonic immobility and Open-field responses were assessed at weeks 4 and 5. Activities of catalase and glutathione peroxidase increased (P < 0.05) in FR + L-serine and AL + L-serine broiler chickens, compared to FR and AL broiler chickens. Latency duration, and rest and frequency of preening increased (P < 0.05) in FR and AL broiler chickens, compared to FR + L-serine and AL + L-serine broiler chickens. Tonic immobility decreased significantly (P < 0.05) in the following order: AL > FR > AL + L-serine > FR + L-serine broiler chickens. The results show that feed restriction and/or L-serine ameliorated the risk of adverse effects of environmental heat stress by increasing catalase and glutathione peroxidase activities; and by decreasing duration of rest, preening frequency, latency of movement and tonic immobility. In conclusion, L-serine administration and feed restriction, particularly in combination, alleviated the adverse heat stress-induced behavioral responses partly by enhancing activities of catalase and glutathione peroxidase.

Breeding indicators for high-yielding field pea under normal and heat stress environments

The warming Canadian summers have become a major abiotic stress to crops, including pea. In the past decade, attempts were made in the understanding of heat stress effect and genomic mapping for heat-responsive traits in field pea. In this study, a new recombinant inbred line population (PR-24) consisting of 39 lines was tested in 6 trials in the summers of 2020 (near normal weather conditions) and 2021 (hot/dry conditions). PR-24 was phenotyped for days to flowering (DTF), days to maturity, plant height, lodging, yield components, plot yield, and seed quality traits. Plant height could be an effective indicator for yield prediction, because its correlation with plot yield was significantly positive in all six trials despite varying degrees of heat and drought stress. Under normal summer weather conditions in 2020, relatively late maturity was correlated with greater seed yield; under heat/drought stress conditions in 2021, successful pod development on the main stem was important for final plot yield. Linkage mapping was used to dissect the genomic regions associated with the measured traits. Four QTLs were identified over multiple trials, one each for DTF (chromosome 7), reproductive node number (chromosome 5), pod number (chromosome 2), and seed protein concentration (chromosome 5). Furthermore, two indices, i.e., stress tolerance index and geometric mean yield, previously used in drought tolerance assessment were validated as useful criteria for heat tolerance assessment in this study.

Acute heat stress amplifies exercise-induced metabolomic perturbations and reveals variation in circulating amino acids in endurance-trained males.

What is the central question of this study? Whole-body substrate utilisation is altered during exercise in hot environments, characterised by increased glycolytic metabolism: does heat stress alter the serum metabolome in response to high intensity exercise? What are the main finding and its importance? Alongside increases in glycolytic metabolite abundance, circulating amino acid concentrations are reduced following exercise under heat stress. Prior research has overlooked the impact of heat stress on protein metabolism during exercise, raising important practical implications for protein intake recommendations in the heat. Using untargeted metabolomics, we aimed to characterise the systemic impact of environmental heat stress during exercise. Twenty-three trained male triathletes ( =64.8±9.2mlkgmin-1 ) completed a 30-min exercise test in hot (35°C) and temperate (21°C) conditions. Venous blood samples were collected immediately pre- and post-exercise, and the serum fraction was assessed via untargeted 1 H-NMR metabolomics. Data were analysed via uni- and multivariate analyses to identify differences between conditions. Mean power output was higher in temperate (231±36W) versus hot (223±31W) conditions (P<0.001). Mean heart rate (temperate, 162±10beatsmin-1 , hot, 167±9beatsmin-1 , P<0.001), peak core temperature (Trec ), core temperature change (ΔTrec ) (P<0.001) and peak rating of perceived exertion (P=0.005) were higher in hot versus temperate conditions. Change in metabolite abundance following exercise revealed distinct clustering following multivariate analysis. Six metabolites increased (2-hydroxyvaleric acid, acetate, alanine, glucarate, glucose, lactate) in hot relative to temperate (P<0.05) conditions. Leucine and lysine decreased in both conditions but to a greater extent in temperate conditions (P<0.05). Citrate (P=0.04) was greater in temperate conditions whilst creatinine decreased in hot conditions only (P>0.05). Environmental heat stress increased glycolytic metabolite abundance and led to distinct alterations in the circulating amino acid availability, including increased alanine, glutamine, leucine and isoleucine. The data highlight the need for additional exercise nutrition and metabolism research, specifically focusing on protein requirements for exercise under heat stress.

Environmental pollution, heat stress and kidney health: a need for integrated assessment.

Environmental pollution, heat stress and kidney health: a need for integrated assessment.

Is the Cooling Vest an Ergogenic Tool for Physically Active Individuals? Assessment of Perceptual Response, Thermo-Physiological Behavior, and Sports Performance: A Systematic Review and Meta-Analysis.

Exercise capacity is limited by environmental heat stress because thermoregulatory systems are altered and cannot prevent the elevation of body temperature due to a complex interplay of physiological, physical, and perceptual alterations. Cooling is an effective strategy to attenuate the temperature rise. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the PEDro scale for assessing methodological quality, we systematically reviewed studies indexed in Medline, Web of Science, EMBASE, Science Direct, Sportdiscus, and Scopus, to evaluate the effects of the cooling vest (CVs) on perceptual response, physiological behavior, and sports performance in adult physical activity practitioners under heat stress conditions. Among the 711 studies identified in the search, 10 studies for the systematic review and eight for the meta-analysis met the inclusion and exclusion criteria. Overall, the use of CVs showed improvements in certain sports performance indicators, being significant (p < 0.05) in test time and substantial in peak power that could be influenced directly by the significant reduction (p < 0.05) in skin temperature and indirectly by the significant improvement (p < 0.05) in thermal and exertional perceptual responses, without the involvement of core temperature. In conclusion, the use of CVs is a cooling technique that influences perceptual response, thermo-physiological behavior, and sports performance. However, further studies are needed to elucidate the relevance of its application to CVs.

Molecular markers for thermo-tolerance are associated with reproductive and physiological traits in Pelibuey ewes raised in a semiarid environment

Pelibuey sheep exhibit reproductive activity through the year, but warm weather lowers their fertility and demonstrates physiological limitations of environmental heat stress. Single nucleotide polymorphisms (SNPs) associated with heat stress tolerance in sheep have been reported previously. The objective was to validate the association of seven thermo-tolerance SNP markers with reproductive and physiological traits in Pelibuey ewes raised in a semiarid region. Pelibuey ewes were assigned to a cool (January 1st.– March 31st.; n = 101) or warm (April 1st.– August 31st.; n = 104) experimental group. All ewes were exposed to fertile rams and assessed for pregnancy diagnosis 90 days later; lambing day was reported at birth. These data served to calculate the reproductive traits of services per conception, prolificacy, days to estrus, days to conception, conception rate and lambing rate. Rectal temperature, rump/leg skin temperature and respiratory rate were measured and reported as physiological traits. Blood samples were collected and processed to extract DNA, which was genotyped using the TaqMan allelic discrimination method and qPCR. A mixed effects statistical model was used to validate associations between SNP genotypes and phenotypic traits. The SNPs rs421873172, rs417581105 and rs407804467 were confirmed as markers associated with reproductive and physiological traits (P < 0.05), and these SNPs were in the genes PAM, STAT1 and FBXO11, respectively. Interestingly, these SNP markers resulted as predictors for the evaluated traits but only in ewes from the warm group, which indicated their association with heat-stress tolerance. An additive SNP effect was confirmed with the highest contribution (P < 0.01) of the SNP rs417581105 for the evaluated traits. Reproductive performance improved (P < 0.05) and physiological parameters decreased in ewes carrying favorable SNP genotypes. In conclusion, three thermo-tolerance SNP markers were associated with improved reproductive and physiological traits in a prospective population of heat-stressed ewes raised in a semiarid environment.

Morpho-Physiological and Biochemical Responses of Field Pea Genotypes under Terminal Heat Stress.

Field pea is one of the important short-duration cool season pulse crops which contributes significantly towards food and nutritional security. Two heat-susceptible (HS) and two heat-tolerant (HT) genotypes were selected from the previous study for further characterization. A significant variation was observed for morpho-physiological traits studied. Principal component analysis explained that first two principal components, i.e., PC1 and PC2 showed 76.5% of the total variance in optimal condition, whereas 91.2% of the total variance was covered by the first two PCs in heat stress environment. The seed yield per plant determined significant and positive association with superoxide dismutase and number of seeds per pod under optimal conditions, whereas under heat stress condition, it was positively associated with number of effective pods per plant, biological yield per plant, proline, pod length, number of seeds per pod, superoxide dismutase, and peroxidase. The significant reduction was noticed in the susceptible genotypes, whereas tolerant genotypes showed stable and non-significant reduction in chlorophyll content. Further, minimum cell damage and higher hydrogen peroxide production was noticed in the susceptible genotypes. In addition, the biochemical characterization of HS and HT genotypes revealed that the higher expression of peroxidase, superoxide dismutase, and catalase modulates the tolerant responses in HT genotypes. These genotypes were further used in developing heat-tolerant field pea genotypes.

A comparative study on feeding timing and additive types of broilers in a high-temperature environment.

Antioxidants such as vitamin C (VC) and green tea extract (GTE) have been reported to have various antioxidant functions and are used as one of the nutritional approaches to alleviate heat stress (HS) in chickens. However, studies on the feeding timing that can produce optimal effects have not been reported. In this study, the stress-relieving effect of VC and GTE addition timing was investigated in high-temperature broiler chickens. A total of 880 1-d-old male chickens were used, and the treatments were as follows: no feed additives provided, CON; VC 250 mg/kg added from 1 d, VC1; GTE 600 mg/kg added from 1 d, GTE1; VC 250 mg/kg added from 22 d, VC22; GTE 600 mg/kg added from 22 d, GTE22. The HS environment was provided for 2 wk from the 22 d and was set at 33 ± 1 °C, 55 ± 10% for 24 h. Feed and water were provided ad libitum. Broiler production was similar in all treatments. In chicken meat quality, the addition of VC and GTE had an effect on meat color and pH (P < 0.05). In particular, GTE had a positive effect on the antioxidant capacity and quality preservation of breast meat (P < 0.05). In blood characteristics, GTE1 significantly lowered the level of total cholesterol, and VC1 affected AST and IgM (P < 0.05). Interestingly, the VC1 group had a positive effect on the maintenance and development of intestinal morphology, a lower rectal temperature, and showed to relieve stress. In conclusion, the addition of VC and GTE has been shown to alleviate the high-temperature stress of broilers, and in the case of VC in particular, feeding from 1 d appeared to alleviate stress more effectively. This study suggests that it is important to determine the appropriate timing of addition of functional substances in order to effectively reduce various stresses that occur in livestock rearing.

Genome Wide Association Study of Yield and Yield-Related Traits in Elite Spring Bread Wheat Genotypes Grown under High Temperature Environment in Sudan

Genetic improvement of wheat for heat tolerance is the main breeding objective in Sudan as it is the principal limiting factor for wheat production. To this end, the availability of wheat genetic diversity is key for success. Genetic diversities and genome-wide association studies were conducted to parse the complex genetic composition of yield-related traits of 250 bread wheat genotypes which were selected from ICARDA’s advanced materials. The genotypes were evaluated under heat stress environment for two seasons (2016/17 and 2017/18) in two sowing dates (optimum and late) at the Gezira Research Farm (GRF), of the Agricultural Research Corporation (ARC), Wad Medani, Sudan. Yield levels ranged from 4016 - 5120 kg/ha for optimum and late sowing dates respectively in the first season and from 5386 - 3926 kg/ha for optimum and late sowing dates respectively in the second season. The top 20 genotypes were better than the best check in the two seasons except, Imam which ranked number 18 in the second season. Two genotypes, genotypes 27 and 37, produced high grain yield in both seasons. Wide ranges of variations among genotypes were found for yield and yield-related traits, including days to heading and maturity, plant height, number of seeds/spike, 1000 seed weight, biomass and harvest index. Genome wide association analyses were performed using 15 kSNPmarkers and the phenotypic data. A total of 282, 355 and 475 significant (P served in the first season, second season and across seasons, respectively. Markers (6B/Kukri_ c27662, 6B/.BobWhite_c23771_525, 6B/Excalibur_c32219_491, 6B/RAC875_c31299_13021302, 6B/BS00046264_51,6A/wsnp_Ex_rep_c69373_68312188, 6A/Tdurum contig12123_1650, 6BKukri_c27662_675 and 6A/BobWhite_c15802_72) on chromosomes 6B and 6A for grain yield were highly significantly associated and stable in every season and across seasons. Highly significant Marker-traits associations (MTAs) were observed for many traits including days to heading and maturity, plant height, number of seeds/spike, 1000 seed weight, biomass and harvest index. The currently identified MTAs should be further validated using other elite sets of genotypes so that they can be used for MAS in the breeding program. The high yielding and heat tolerant genotypes identified in this study will be evaluated across key locations in Sudan for potential release in Sudan. Furthermore, they will be used as parents in the breeding program for heat tolerance.

Thermophysiological and Perceptual Responses of Amateur Healthcare Workers: Impacts of Ambient Condition, Inner-Garment Insulation and Personal Cooling Strategy

While personal protective equipment (PPE) protects healthcare workers from viruses, it also increases the risk of heat stress. In this study, the effects of environmental heat stress, the insulation of the PPE inner-garment layer, and the personal cooling strategy on the physiological and perceptual responses of PPE-clad young college students were evaluated. Three levels of wet bulb globe temperatures (WBGT = 15 °C, 28 °C, and 32 °C) and two types of inner garments (0.37 clo and 0.75 clo) were chosen for this study. In an uncompensable heat stress environment (WBGT = 32 °C), the effects of two commercially available personal cooling systems, including a ventilation cooling system (VCS) and an ice pack cooling system (ICS) on the heat strain mitigation of PPE-clad participants were also assessed. At WBGT = 15 °C with 0.75 clo inner garments, mean skin temperatures were stabilized at 31.2 °C, Hskin was 60-65%, and HR was about 75.5 bpm, indicating that the working scenario was on the cooler side. At WBGT = 28 °C, Tskin plateaued at approximately 34.7 °C, and the participants reported "hot" thermal sensations. The insulation reduction in inner garments from 0.75 clo to 0.37 clo did not significantly improve the physiological thermal comfort of the participants. At WBGT = 32 °C, Tskin was maintained at 35.2-35.7 °C, Hskin was nearly 90% RH, Tcore exceeded 37.1 °C, and the mean HR was 91.9 bpm. These conditions indicated that such a working scenario was uncompensable, and personal cooling to mitigate heat stress was required. Relative to that in NCS (no cooling), the mean skin temperatures in ICS and VCS were reduced by 0.61 °C and 0.22 °C, respectively, and the heart rates were decreased by 10.7 and 8.5 bpm, respectively. Perceptual responses in ICS and VCS improved significantly throughout the entire field trials, with VCS outperforming ICS in the individual cooling effect.