Effect of room temperature and dietary amino acid concentration on performance of lactating sows. NCR-89 Committee on Swine Management.
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Mixed-parity sows (n = 267) from five research stations were used to investigate whether a reduction of excess dietary amino acids would improve feed intake and performance of lactating sows experiencing heat stress. Experimental treatments included effects of room temperature (warm or hot) and diet (adequate protein [AP] or low protein [LP]). The corn-soybean meal AP diet was formulated to contain 16.5% CP, .8% lysine, and .67% digestible lysine. The LP diet was formulated to contain 13.7% CP, .76% lysine, and .66% digestible lysine using corn, soybean meal, and synthetic lysine. Feed intake during gestation was standardized at 1.8 kg x sow(-1) x d(-1). At parturition, litter size was adjusted to no fewer than nine pigs. Mean high temperature in the warm and hot rooms was 20.4 and 29.2 degrees C and mean low temperature was 17.7 and 27.1 degrees C, respectively. The hot environment reduced (P < .01) feed intake of sows (4.19 vs 6.38 kg/d) during lactation, weaning weight of sows (176.2 vs 193.6 kg), percentage of sows displaying estrus (79.2 vs 93.4%) by d 15 postweaning, and litter growth rate (1.74 vs 2.11 kg/d) and increased (P < .01) respiration rate of sows on d 10 postpartum (71.9 vs 36.5 breaths/min) compared with the warm environment. Litter size and backfat loss of sows were not affected by treatments. No significant diet x room temperature interactions were observed for voluntary feed intake, body weight loss, backfat loss, or respiration rate of sows. Litter growth rate was depressed by feeding the LP diet in the warm room but was improved by feeding the LP diet in the hot room (warm-AP, 2.17; warm-LP, 2.05; hot-AP, 1.71; hot-LP, 1.77 kg/d; P < .05). Reduction of dietary crude protein combined with supplementation of crystalline lysine to reduce concentrations of excess dietary amino acids did not significantly reduce heat stress of sows, but it did support slight improvements in weight gain of litters nursing heat-stressed sows. (+info)
Heat shock disrupts long-term memory consolidation in Caenorhabditis elegans.
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Previous work has demonstrated that memory for habituation training is retained for > 24 hr in Caenorhabditis elegans. In this study the timing of memory consolidation was investigated by introducing heat shock (32 degrees C, 45 min) either before training, long after training, or during training. It was found that memory consolidation was disrupted by heat shock during training but not before or after training. In addition, heat shock before training failed to induce thermal tolerance to the effects of heat shock during training on long-term memory formation. When brief heat shock (32 degrees C, 15 min) was presented during training at different intervals, the results suggested that a narrow critical period for memory consolidation of habituation may exist. These findings demonstrate that in C. elegans long-term memory for habituation is disrupted by a temporally defined agent, heat shock. Therefore, heat shock can be used as a fine-grained tool to investigate the dynamics of memory consolidation. (+info)
Heat balance when wearing protective clothing.
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This issue of the Annals of Occupational Hygiene is dedicated to the topic of heat stress evaluation. For this evaluation, several evaluation programs and international standards are available. In order to understand the reasoning and underlying theory behind these programs and standards, a basic knowledge of heat exchange processes between workers and their environment is needed. This paper provides an overview of the relevant heat exchange processes, and defines the relevant parameters (air and radiant temperature, humidity, wind speed, metabolic heat production and clothing insulation). Further it presents in more detail the relation between clothing material properties and properties of clothing ensembles made from those materials. The effects of clothing design, clothing fit, and clothing air permeability are discussed, and finally an overview of methods for the determination of clothing heat and vapour resistance is given. (+info)
International standards for the assessment of the risk of thermal strain on clothed workers in hot environments.
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The International Standards Organisation (ISO) has produced an integrated series of international standards for the assessment of human responses to thermal environments. They include standards for the assessment of thermal comfort, heat stress and cold stress and many have been adopted as European and British standards. This paper describes the series of standards and in particular those concerned with the assessment of risk in hot environments. A three tier approach is taken which involves a simple thermal index that can be used for monitoring and control of hot environments (ISO 7243), a rational approach which involves an analysis of the heat exchange between a worker and his or her environment (ISO 7933) and a standard that describes the principles of physiological measurement which can be used in the establishment of personal monitoring systems of workers exposed to hot environments (ISO 9886). The standards are self-contained and can be used independently. In any comprehensive assessment however they would be used in conjunction. The simple index provides a first stage analysis and can confirm whether or not there is likely to be unacceptable thermal strain. Where a more detailed analysis is required then ISO 7933 provides an analytical method that can provide a more extensive assessment and interpretation leading to recommendations for improvement to the working environment. Where a method needs to be confirmed, or conditions are beyond the scope of ISO 7243 and ISO 7933, then ISO 9886 provides guidance on physiological measurement and interpretation. This would be used in extreme environments where individual responses are required to ensure health and safety or, in the case where personal protective equipment (PPE) is worn, which is beyond the scope of ISO 7243 and ISO 7933. The ISO system therefore covers almost all exposures to hot environments. It would be useful however to extend the scope of the standards that provide a simple index or analytical approach. This paper describes the current standards and their scope and forms the basis and background for descriptions of proposed extensions to the scope of the standards described in other papers in this special issue. (+info)
Development of a draft British standard: the assessment of heat strain for workers wearing personal protective equipment.
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Existing methods for estimating heat stress, enshrined in British/International Standards (the Wet Bulb Globe Temperature (WBGT) index [BS EN 27243] and the Required Sweat Rate equation [BS EN 12515; ISO 7933 modified]), assume that the clothing worn by the individual is water vapour permeable; the WBGT index also assumes that the clothing is relatively light. Because most forms of personal protective equipment (PPE) either have a higher insulative value than that assumed or are water vapour impermeable, the Standards cannot be accurately applied to workers wearing PPE. There was, therefore, a need to develop a British Standard which would allow interpretation of these existing Standards for workers wearing PPE. Relevant information was obtained through reviewing the literature and consulting experts. Two questionnaire surveys of potential users of the Standards were conducted, and physiological data collected both experimentally and in work situations were considered. The information collected was used to develop the draft British Standard. It provides information and data on: The general effect of PPE on heat balance of the body (the ability of the body to maintain its 'core' temperature within an acceptable range). The effect of specific forms of PPE on metabolic heat production rate. The thermal insulation and evaporative resistance of types of PPE. The effect of the closure of the garments to the body on heat transfer. The effect of the PPE on the proportion of the body covered. The effect of an air supply (for example, Breathing Apparatus [BA]) to the wearer. Guidance is given on conducting an analysis of the work situation, taking account of the impact of PPE. Detailed methods of interpreting both BS EN 27243 and BS EN 12515 for workers wearing PPE are given, taking account of the factors listed above. Three worked examples using BS EN 27243 and BS EN 12515 are given in the Annex of the draft Standard. (+info)
Heat stress and protective clothing: an emerging approach from the United States.
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There is little doubt that heat stress affects many workers adversely and that protective clothing generally adds to the burden. The ACGIH threshold limit value for heat stress is the guiding document for evaluation of heat stress in the United States. Adjustment factors have been used to reflect the change in heat stress imposed by different clothing ensembles. While the first proposed factors started with limited experimental data and professional judgment, heat balance methods in the laboratory have yielded better estimates of adjustment factors and for a wider selection of ensembles. These same experiments have provided the starting point to accounting for nonporous clothing in heat balance evaluation schemes such as required sweat rate. Proposed changes to the ACGIH TLV have been mentioned and a framework for thinking about controls presented. (+info)
Clothing convective heat exchange--proposal for improved prediction in standards and models.
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Convection is an important determinant for both sensible and evaporative heat exchange. Heat transfer by convection for normal boundary conditions is readily described by simple power functions. Clothing affects convection in various ways and existing characterisation of clothing by its static insulation values produces inaccurate prediction of sensible heat exchange, eventually leading to erroneous risk assessment. The present paper reviews various methods for evaluation of clothing convective (sensible) heat exchange. Based on available data, two equations are proposed for determination of the reduction of the total insulation values obtained under static, still wind conditions as a consequence of wind and walking effects. The equations apply from 0 to 1.84 clo, from 0.2 to 3 m/s and for walking speeds up to 1.2 m/s. The equations are incorporated in ISO 7933 to provide a more realistic and accurate prediction of sensible heat transfer through clothing. (+info)
Clothing evaporative heat resistance--proposal for improved representation in standards and models.
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Clothing heat and vapour resistance are important inputs for standards and models dealing with thermal comfort, heat- and cold-stress. A vast database of static clothing heat resistance values is available, and this was recently expanded with correction equations to account for effects of movement and wind on the static value of heat resistance in order to obtain the dynamic heat resistance of clothing ensembles. For clothing vapour resistance, few data were available so far. Indices for vapour permeability (im) and reduction factors for vapour transfer (Fpcl) of clothing were used instead, using a relation between heat and vapour resistance to derive the clothing vapour resistance from the value for clothing heat resistance. This paper reviews the two commonly used approaches (im and Fpcl), as well as five alternative approaches to the problem. The different approaches were evaluated for their accuracy and their usability. The present paper shows that the currently used relations are not adequate when the wearer of the clothing starts moving, or is exposed to wind. Alternative approaches are shown to improve the determination of dynamic clothing vapour resistance, though some are thought to be too complex. An empirical description of the relation between the clothing permeability index (im) and the changes in clothing heat resistance due to wind and movement was selected as the most promising method for deriving clothing vapour resistance. For this method the user needs to know the static heat resistance, the static im value of the clothing and the wind- and movement-speed of the wearer. This method results in a predicted maximal decrease in clothing vapour resistance by 78%, when clothing heat resistance is reduced by 50%, which is consistent with theoretical expectations and available data. (+info)