Heat Stress Problems Research Articles

Grain filling patterns of barley as affected by high temperature stress

Grain filling determines the grain weight, a major component of grain yield in cereals. Grain filling in barley depends on current assimilation and culm reserves (mainly water-soluble carbohydrates). Nowadays barley is facing heat stress problem which is mostly responsible to reduce the yield of barley. A field experiment was conducted at the Field Lab, Department of Crop Botany, BangladeshAgriculturalUniversity, Mymensingh during November 2015 to March 2016 to study the grain filling patterns and the contributions of culm reserves to grain yield under heat stress. The experiment consisted of two factors—barley cultivars and heat stress. The heat stress was imposed by late sowing. The tillers were sampled once a week during grain filling period to determine the changes in dry weights of different parts, viz., leaves, culm with sheath, spikes, and grains; and to examine the contribution of culm reserves to grain yield. The results in the experiment revealed that the grain yield was reduced by 22-28% due to the stress. The grain yield varied from 52 to 150 g m−2 with the mean of 102 g m−2 under control while it varied from 37 to 116 g m−2 with the mean of 75 g m−2 under heat stress. Among the cultivars studied BARI Barley5, BARI Barley2 and BARI Barley1, seemed as high yielders while BARI Barley3, BARI Barley4, BARI Barley6 as the low yielders under heat stress treatment. The reduction in grain yield was attributable mainly to lighter grain weight due to the stress. Heat stress drastically reduced the grain filling duration by 45–50%. However, the stress increased the grain filling rate by 6–53%. The amount of reserves remobilized to grain varied among the cultivars ranging from 4.8 to 12.77 mg spike−1 in control and from 1.73 to 6.25 mg spike−1 in stressed plants. The stressed barley plants exhibited lower accumulation of reserves in culm but they showed almost its complete remobilization to the grain. The contribution of culm reserves to grain yield varied from 1.13 to 19.52%, and 1.09 to 2.11% in control and in stressed plants, respectively. In conclusion, culm reserve is the important attributes in grain yield in Bangladeshi barley cultivars but the contribution remains almost unaffected due the post-anthesis heat stress.J. Bangladesh Agril. Univ. 15(2): 174-181, December 2017

A wedge strategy for mitigation of urban warming in future climate scenarios

Abstract. Heat stress is one of the most severe climate threats to human society in a future warmer world. The situation is further exacerbated in urban areas by urban heat islands (UHIs). Because the majority of world's population is projected to live in cities, there is a pressing need to find effective solutions for the heat stress problem. We use a climate model to investigate the effectiveness of various urban heat mitigation strategies: cool roofs, street vegetation, green roofs, and reflective pavement. Our results show that by adopting highly reflective roofs, almost all the cities in the United States and southern Canada are transformed into white oases – cold islands caused by cool roofs at midday, with an average oasis effect of −3.4 K in the summer for the period 2071–2100, which offsets approximately 80 % of the greenhouse gas (GHG) warming projected for the same period under the RCP4.5 scenario. A UHI mitigation wedge consisting of cool roofs, street vegetation, and reflective pavement has the potential to eliminate the daytime UHI plus the GHG warming.

Reconsidering betaine as a natural anti-heat stress agent in poultry industry: a review

Betaine is found ubiquitously in plants, animals, microorganisms, and rich dietary sources including seafood, spinach, and wheat bran. The chief physiological role of betaine is to function as a methyl donor and an osmolyte. Betaine also acts as an osmolyte,to maintain the avian's cellular water and ion balance to improve the avian's capacity against heat stress via preventing dehydration and osmotic inactivation. It helps in maintaining the protective osmolytic activity, especially in heat-stressed birds. Betaine may promote various intestinal microbes against osmotic variations and thus improve microbial fermentation activity. Previous studies showed that dietary supplementation of betaine in poultry diets could positively affect nutrients' digestibility, reduce abdominal fat weight, and increase breast meat yield. In addition, betaine has been reported to protect internal organs and boost their performance. Its inclusion in poultry diet is sparing essential amino acids like choline and methionine. In addition, it may play an important role in lean meat production by positively affecting the lipid metabolism with increased fatty acids catabolism and thus reducing carcass fat deposition. The aim of this review article was to broaden the knowledge regarding betaine and its importance in the poultry industry to cope with the heat stress problem. Moreover, it should be added to the diet as a natural anti-stressor through different routes (water/feed) to overcome the heat stress problem. However, further studies need to be conducted at the genetic and molecular basis to elucidate the mechanism behind the betaine as a natural anti-heat agent to decrease the heat stress problem in the poultry industry.

Ameliorating Effect of Herbal Antistressor Products on the Growth and Carcass Parameters of Japanese Quails Reared Under Heat Stress

The performance of the birds tends to decline during summer due to heat stress. In order to address the problem of heat stress, an experiment was conducted to investigate the effect of different herbal antistressor products on the growth performance of quails. For this, 120 day-old Japanese quails were randomly divided into four treatment groups with six replicates of five birds each. The experimental design consisted of T1: control, T2: Stressroak liquid, T3: AV/ESL/16 liquid, T4: Geriforte liquid. The results indicated that control group had significantly (P0.05). The feed conversion ratio improved significantly (P>0.05) in herbal antistressor supplemented groups compared to the control. There was no significant (P>0.05) effect on various carcass parameters studied, except for abdominal fat percentage which was significantly (P

Assessment of Outdoor Thermal Comfort and Wind Characteristics at Three Different Locations in Peninsular Malaysia

Urbanization and rapid growth in construction have led to the problems of global warming and urban heat island throughout the world. In order to reduce these problems particularly in hot and humid climatic region, a research on current level of outdoor thermal comfort and wind characteristics based on the local weather conditions around Malaysia should be conducted. This paper reports on the analysis of outdoor thermal comfort level at hottest temperatures and wind characteristics at three locations in Peninsular Malaysia by using hourly climatic data recorded by Malaysian Meteorological Department (MetMalaysia). The level of outdoor thermal comfort was assessed based on the Universal Thermal Climate Index (UTCI). The results showed extreme heat stress conditions have occurred at Alor Setar, Kuantan, and Subang with UTCI values of 51.2°C, 49.7°C, and 49.0°C respectively taking into account only temperature data from the year 2012 to 2014. However, for 20 years data from 1994 to 2014, the calculated UTCI also showed extreme heat stress conditions with their respective values of 49.6°C, 43.8°C, and 49.7°C for Alor Setar, Kuantan, and Subang respectively. Meanwhile, the hourly mean wind speed for three years data at Alor Setar, Kuantan, and Subang, were 1.70m/s, 1.69m/s, and 1.63m/s respectively. The highest mean wind speed of 11.6m/s was observed at Subang, while no wind movement (i.e. 0m/s) was considered to be the lowest hourly wind speed for all three locations. The observed prevailing wind direction for all the three locations was from the north (0°). It can be concluded that Peninsular Malaysia is generally facing extreme heat stress problem due to unfavourable climatic conditions.

English

As the body temperature of birds rise, feed consumption, growth rate, feed efficiency, survivability, egg production and egg quality tends to decline. In order to address the problem of heat stress, an experiment was conducted to determine the effect of AV/LAP/19 liquid (Supplied by M/s Ayurvet Ltd. Baddi, HP, India) containing natural vitamin C with bioflavonoids and selenium, and synthetic ascorbic-acid (vitamin C) supplementation on the performance of commercial layers. 120 birds, 55 weeks of age were divided into 4 equal groups of 30 birds each. They were exposed to a heat stress of 39±8°C temperature and temperature humidity index (THI) of 81.33±1.20. All bird groups were offered basal diet deficient in vitamin C. Negative effect of high ambient temperature and relative humidity was evidenced from the high serum cortisol level (mg/L) (3.42±0.19 to 3.67±0.20) in all groups. It was significantly optimized and lowered down in all treated groups. Concomitantly, increased alkaline phosphatase and alkaline transaminase levels were also lowered in treated birds. The total protein, albumin and globulin were having numerically higher levels in treated birds. It was concluded that the herbal liquid AV/LAP/19 at both dosages ameliorated the heat stress in layer birds as well as resulted in better feed efficiency and immunomodulation. However, significantly better egg production (%) was recorded in the birds supplemented with AV/LAP/19. Key words: AV/LAP/19, heat stress, herbal products, egg production, vitamin C.

A Conjugate Heat and Mass Transfer Model to Evaluate the Efficiency of Conductive Cooling for Dairy Cattle

Abstract. Heat stress will cause a dairy cow that is highly productive under normal conditions to produce far less milk and also to delay its gestation cycle. The corresponding economic losses have become significant as the dairy industry, following the population growth in the U.S., expands into warmer climatic zones. Global warming, higher energy costs, and ever more scarce water resources will further exacerbate the heat stress problem in the foreseeable future. Currently in use systems designed to mitigate heat stress work well under certain conditions, but as temperature and humidity levels rise, most such systems lose their ability to prevent heat stress. The present study investigates the efficacy of using a heat exchanger placed underneath the stall bedding to alleviate the conditions that lead to heat stress. The computational model incorporates physiological and physical characteristics of a cow as well as specific heat and mass transport mechanisms including non-Darcy flow and sweating. The results show that a system that employs conductive cooling could alleviate heat stress during hot and humid weather even when conventional systems cannot.

Association between Heat Stress and Occupational Injury among Thai Workers: Findings of the Thai Cohort Study

Global warming will increase heat stress at home and at work. Few studies have addressed the health consequences in tropical low and middle income settings such as Thailand. We report on the association between heat stress and workplace injury among workers enrolled in the large national Thai Cohort Study in 2005 (N=58,495). We used logistic regression to relate heat stress and occupational injury separately for males and females, adjusting for covariate effects of age, income, education, alcohol, smoking, Body Mass Index, job location, job type, sleeping hours, existing illness, and having to work very fast. Nearly 20% of workers experienced occupational heat stress which strongly and significantly associated with occupational injury (adjusted OR 2.12, 95%CI 1.87-2.42 for males and 1.89, 95%CI 1.64-2.18 for females). This study provides evidence connecting heat stress and occupational injury in tropical Thailand and also identifies several factors that increase heat exposure. The findings will be useful for policy makers to consider work-related heat stress problems in tropical Thailand and to develop an occupational health and safety program which is urgently needed given the looming threat of global warming.

Vermeidung von Hitzestress - Baulich-technische Möglichkeiten in Schweineställen

The heat stress problems of last summer left a lasting impression. While the inside pig house temperature was increasing from day to day, food intake and production levels were decreasing correspondingly. By taking various constructional and technical fund

Physiological responses of firefighters wearing level 3 chemical protective suits while working in controlled hot environments.

Firefighters in Queensland are exposed to hot, humid weather conditions that contribute to the overall workload encountered during emergency operations. Responding to certain hazardous material incidents requires firefighters to wear fully encapsulated chemical protective suits for a maximum period of 20 minutes. The nature of these suits, combined with workload and environmental conditions, poses a potential heat stress problem for firefighters. This study evaluates the heat-induced physiological responses of firefighters while wearing fully encapsulated chemical protective suits in a series of controlled thermal environments. Heart rate, body (aural) temperature, blood pressure, fluid loss, and a rating of perceived exertion were measured to evaluate the effect of increasing ambient air temperature during the performance of standard tasks. The results of the study indicated that the significant increase in heart rate, body temperature, and blood pressure was directly related to the increase in air temperature. The research indicates that the recommended suit wearing time of 20 minutes provided adequate physiological protection under the research conditions.

STRATEGY OF ANALYSIS AND INTERPRETATION OF THERMAL WORKING CONDITIONS

This paper proposes a strategy for the management of heat problems at the workplace. This includes three steps of analysis: the first aims at recognizing the problem and classifying it under one of the categories--comfort, discomfort but no health risk, or health risk either in the long term or in the short term. The second is designed to evaluate the magnitude of the problem and to optimize the choice of solutions. The interpretation of the data is based on analytical indices: the PMV-PPD indices for heat discomfort conditions and the Required Sweat Rate index for heat stress conditions. The third step involves an in-depth analysis of the situation: this will be undertaken only if a major problem of heat stress has been detected at the previous stage and providing technical solutions cannot be immediately implemented. The advantages and possible limitations of this step-by-step approach are outlined and its cost effectiveness is discussed in the perspective of a true management of health and safety at work.

The physiologic determination of the vapor permeation efficiency of clothing

Two calculations of the coefficient for vapor permeation efficiency ( F pcl ) have been proposed for use in the rational (heat balance) approach to heat stress problems caused by wearing protective clothing—one proposed by Candas et al. (1987) and a second (derived from K e η′ ) proposed by Kenney et al. (1987). Both of these coefficients are based on the concept of sweating efficiency and each is used in the calculation of E max , the maximal evaporative capacity of the environment. This paper compares these 2 approaches based on data collected across several clothing ensembles common to industry. In general, the lighter and more permeable the ensemble, the closer the agreement between the two coefficients. However, as clothing becomes impermeable (e.g., vapor-barrier clothing made of plastic, coated Tyvek®, etc.), use of the former F pcl significantly overestimates E max . It is suggested that either calculation can be used for lightweight clothing (although Candas F pcl is simpler to calculate) but that the F pcl calculated by Kenney and co-workers is preferable for heavier ensembles.

The loss of functional body hair in man: the influence of thermal environment, body form and bipedality

An insulating layer of body hair is crucial to the thermoregulatory energetics of most mammals. Only some highly specialized aquatic forms and a few fossorial and terrestrial species which experience special heat stress problems have evolved a naked skin. Man's body size and form suggest that his naked skin is associated with the prevention of hyperthermia in hot climates rather than an aquatic ancestry. The reduced direct solar radiation exposure of hominids in open equatorial environments, resulting from their unique bipedal posture, may explain the absence of this characteristic among other savannah mammals of comparable body mass.