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1.
Aerosp Med Hum Perform ; 95(4): 223-225, 2024 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-38486320

RESUMO

BACKGROUND: In the early days of the National Aeronautics and Space Administration (NASA), medicine in support of the astronauts was led by military experts from the U.S. Air Force as well as experts from the U.S. Navy and U.S. Army. In the early years, a physician with expertise in aerospace medicine was assigned to the Space Task Group and then to NASA. One of these individuals was Dr. Stanley White, a U.S. Air Force physician. To capture more of the early space medicine pioneers, a contract was established between the National Library of Medicine and the principal investigator at the University of Cincinnati to conduct a series of interviews with these early pioneers. An interview with Dr. White took place in his home while he was in hospice care. This audiotaped interview and other written and oral histories within NASA archives and the literature were reviewed to support this work. A series of questions were prepared for the interaction with Dr. White. These questions provided further clarification on his background and contribution. Responses to questions elicited open-ended discussion. The conversation provided a historical summary of Dr. White's contribution to NASA as one of its first flight surgeons.Doarn CR. An interview with Dr. Stanley White, one of NASA's first flight surgeons. Aerosp Med Hum Perform. 2024; 95(4):223-225.


Assuntos
Medicina Aeroespacial , Voo Espacial , Cirurgiões , Humanos , Masculino , Astronautas , Estados Unidos , United States National Aeronautics and Space Administration
3.
Sci Rep ; 13(1): 16356, 2023 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-37773513

RESUMO

Complex assembly tasks with multiple manual operations and steps often require rapid judgment and action under time pressure and cause most human-related errors. The task switching and action transitions are major sources of these errors. This study intends to implement an electroencephalography (EEG) approach to quantitatively evaluate the mental workload during task switching and transition. The time-frequency and spectrum analysis were utilized to compute and reflect the task demand between the intervals of individual tasks. This study developed an experiment to validate the proposed assessment approach and benchmark the results with the National Aeronautics and Space Administration task load index (NASA-TLX) subjective evaluation scale analysis. The results show that the average value of the power spectral densities (PSDs) of the gamma band signal of the AF4 channel and the beta band signal of Channel F3 show distinctive signal patterns among task stages and intervals. During the interval between the idling stage and the part selection stage, the peak of the PSD envelope increased from 18 to 27 Hz, suggesting advanced cognition increases the mental workload of the interval between different tasks. Therefore, the task switching period cannot be regarded as rest and need to be optimized with better task organization.


Assuntos
Análise e Desempenho de Tarefas , Carga de Trabalho , Estados Unidos , Humanos , Cognição , Julgamento , United States National Aeronautics and Space Administration
4.
J Dairy Sci ; 106(10): 6995-7007, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37562648

RESUMO

Heat stress is a prominent issue in livestock production, even for intensively housed dairy herds in Canada. Production records and meteorological data can be combined to assess heat tolerance in dairy cattle. The overall aim of this study was to evaluate the possibility of genetic evaluation for heat tolerance in Canadian dairy cattle. The 2 specific objectives were (1) to estimate the genetic parameters for milk, fat, and protein yield for Holsteins while accounting for high environmental heat loads, and (2) to determine if a genotype-by-environment interaction causes reranking of top-ranked sires between environments with low and high heat loads. A repeatability test-day model with a heat stress function was used to evaluate the genetic merit for milk, fat, and protein yield under heat stress and at thermal comfort for first parity in 5 regions in Canada. The heat stress function for each trait was defined using a specific temperature-humidity index (THI) threshold. The purpose of this function was to quantify the level of heat stress that was experienced by the dairy cattle. The estimated genetic correlation between the general additive genetic effect and the additive effect on the slope of the change in the trait phenotype for milk, fat, and protein yield ranged from -0.16 to -0.30, -0.20 to -0.44, and -0.28 to -0.42, respectively. These negative correlations imply that there is an antagonistic relationship between sensitivity to heat stress and level of production. The heritabilities for milk, fat, and protein yield at 15 units above the THI threshold ranged from 0.15 to 0.27, 0.11 to 0.15, and 0.11 to 0.15, respectively. Finally, the rank correlations between the breeding values from a repeatability model with no heat stress effect and the breeding values accounting for heat stress for the 100 top-ranked bulls indicated possible interaction between milk production traits and THI, resulting in substantial reranking of the top-ranked sires in Canada, especially for milk yield. This is the first study to implement weather data from the NASA POWER database in a genetic evaluation of heat tolerance in dairy cattle. The NASA POWER database is a novel alternative meteorological resource that is potentially more reliable and consistent and with broader coverage than weather station data increasing the number of animals that could be included in a heat stress evaluation.


Assuntos
Doenças dos Bovinos , Transtornos de Estresse por Calor , Termotolerância , Gravidez , Feminino , Estados Unidos , Masculino , Bovinos/genética , Animais , Termotolerância/genética , Lactação/genética , United States National Aeronautics and Space Administration , Temperatura Alta , Canadá , Tempo (Meteorologia) , Leite/metabolismo , Umidade , Transtornos de Estresse por Calor/veterinária , Doenças dos Bovinos/metabolismo
5.
Life Sci Space Res (Amst) ; 38: 1-7, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37481303

RESUMO

As part of planning for future space exploration, COSPAR (The Committee on Space Research) together with participating space agencies, organized and held interdisciplinary meetings to consider next steps in addressing knowledge gaps for planetary protection for future human missions to Mars. Beginning with the results of these meetings and earlier work by NASA, ESA, and COSPAR (e.g., Criswell et al., 2005; Hogan et al., 2006; Rummel et al., 2008) as a base the authors of this paper carried out a follow-on NASA planning activity to identify the necessary steps to be accomplished to close knowledge gaps. We identified significant overlap between the planetary protection needs and other sets of Mars preparation roadmaps (1) microbial monitoring requirements for crew health and medical systems, (2) studies of the microbiome of the built environment, (3) environmental control and life support systems (ECLSS), (4) waste management, and (5) planetary surface operations. In many cases, efforts to mature exploration class systems for Mars that are occurring in other domains can be leveraged with minor changes to address planetary protection gaps as well. In other cases, work planned for testing on the International Space Station (ISS) as an analog for crew Mars transit, or on the lunar surface as an analog for Mars surface operations can be used to close planetary protection technology and knowledge gaps. An overall strategic framework that combines these domains has the advantage of being more comprehensive, efficient, and timely for closing gaps. This approach has led to the development of a NASA roadmap for addressing planetary protection integrated with other related roadmaps. NASA's development and execution of the planetary protection is now viewed in an integrated way with related technology development and testing. Key features of the integrated capabilities roadmap include.


Assuntos
Marte , Microbiota , Voo Espacial , Estados Unidos , Humanos , United States National Aeronautics and Space Administration , Lua
6.
Life Sci Space Res (Amst) ; 38: 19-28, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37481304

RESUMO

BioSentinel is a nanosatellite deployed from Artemis-I designed to conduct in-situ biological measurements on yeast cells in the deep space radiation environment. Along with the primary goal of measuring damage and response in cells exposed during spaceflight, on-board active dosimetry will provide measurements of the radiation field encountered behind moderate shielding provided by the BioSentinel housing and internal components. The measurements are particularly important to enable interpretation of biological observations but also provide an opportunity to validate integrated computational models used to calculate radiation environments. In this work, models are used to predict the galactic cosmic ray exposure anticipated for the BioSentinel payload and on-board dosimeter. The model calculations presented herein were completed prior to the Artemis-I launch on November 16, 2022, and therefore represent actual predictions (i.e., unbiased by a priori knowledge of on-board measurements). Such time-forward predictions are rarely performed for space radiation applications due to limitations of environmental models, but truly independent model validation will be possible in the future when on-board measurements become available. The method used to facilitate future projections within an existing GCR (galactic cosmic ray) environmental model is described, and projection uncertainties are quantified and contextualized.


Assuntos
Radiação Cósmica , Voo Espacial , Estados Unidos , United States National Aeronautics and Space Administration , Radiometria , Modelos Teóricos
7.
Astrobiology ; 23(8): 880-887, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37384923

RESUMO

Abstract Responsible space exploration is a cornerstone of planetary protection, particularly at sites in the Solar System with a high potential for the existence of extant life. To limit bioburden, spacecraft assembly occurs in cleanroom facilities. Cleanroom levels are established through air particulate counters that can assess particle size distribution and concentration but cannot detect bioaerosols. Additionally, these devices do not detect in real-time, which poses a risk to critical flight hardware assemblies or even mission timelines. A first-of-its-kind study was conducted to simultaneously detect bioaerosols, inert particles, and their size distribution in real-time in operational spacecraft assembly cleanrooms at NASA's Jet Propulsion Laboratory in Pasadena, CA, USA, using the BioVigilant IMD-A® 350 (Azbil Corporation, Tucson, AZ, USA). The IMD-350A continuously sampled during operations and no-operation 6 h intervals in two facilities per cleanroom class: ISO 6, ISO 7, and ISO 8. A positive correlation was established between human presence in the cleanroom and elevated bioaerosol counts. Smaller particles of sizes 0.5 and 1 µm constituted an average ∼91% of the total bioaerosols detected in At Work intervals across all ISO classes observed. The results of this study were used to establish bioburden particulate thresholds for the most stringent JPL cleanrooms used in the assembly of the Sample Caching System for the Mars 2020 Perseverance rover.


Assuntos
Voo Espacial , Astronave , Estados Unidos , Humanos , United States National Aeronautics and Space Administration , Ambiente Controlado , Planetas , Poeira
8.
Proc Inst Mech Eng H ; 237(7): 869-878, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37313977

RESUMO

The relationship framework between electroencephalogram (EEG) signals and subjective perception during pilots' missions was established to improve pilots' training efficiency and flight safety. Primarily, this study constructs a real flight scene through virtual reality (VR) and then obtains EEG data in simulated scenes. Researchers use VR technology to build a mission simulation room and then acquire EEG data from participants wearing EEG acquisition devices in the simulated room. The experimental process is divided into flight simulation and a questionnaire survey. Based on the participants' EEG analysis, the researchers verified the changes of ß rhythm under a high-difficulty operation mission. In addition, this study infers the mechanism of affecting pilots' mental workload under high-difficulty operation by analyzing the correlation between subjective questionnaire results and ß rhythms. The results showed that in the context of pilots performing flight missions in the aircraft space environment, the pilots' mental load had the most excellent rhythmic relationship with the regions representing ß rhythm. Therefore, a comprehensive experimental framework constructed in this study based on virtual simulation space to analyze the relationship between EEG and NASA-TLX subjective questionnaire provides a set of more accurate reference information for the design of a pilot training system based on pilot training efficiency and flight safety.


Assuntos
United States National Aeronautics and Space Administration , Realidade Virtual , Estados Unidos , Humanos , Aeronaves , Carga de Trabalho , Eletroencefalografia
9.
Int J Biometeorol ; 67(7): 1273-1277, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37191730

RESUMO

Heat stress negatively affects livestock, with undesirable effects on animals' production and reproduction. Temperature and humidity index (THI) is a climatic variable used worldwide to study the effect of heat stress on farm animals. Temperature and humidity data can be obtained in Brazil through the National Institute of Meteorology (INMET), but complete data may not be available due to temporary failures on weather stations. An alternative to obtaining meteorological data is the National Aeronautics and Space Administration Prediction of Worldwide Energy Resources (NASA POWER) satellite-based weather system. We aimed to compare THI estimates obtained from INMET weather stations and NASA POWER meteorological information sources using Pearson correlation and linear regression. After quality check, data from 489 INMET weather stations were used. The hourly, average daily and maximum daily THI were evaluated. We found greater correlations and better regression evaluation metrics when average daily THI values were considered, followed by maximum daily THI, and hourly THI. NASA POWER satellite-based weather system is a suitable tool for obtaining the average and maximum THI values using information collected from Brazil, showing high correlations with THI estimates from INMET and good regression evaluation metrics, and can assist studies that aim to analyze the impact of heat stress on livestock production in Brazil, providing additional data to complement the existing information available in the INMET database.


Assuntos
Transtornos de Estresse por Calor , Meteorologia , Animais , Estados Unidos , Feminino , Umidade , Temperatura , Brasil , United States National Aeronautics and Space Administration , Tempo (Meteorologia) , Transtornos de Estresse por Calor/veterinária , Temperatura Alta , Lactação , Leite
10.
Astrobiology ; 23(8): 897-907, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37102710

RESUMO

Molecular biology methods and technologies have advanced substantially over the past decade. These new molecular methods should be incorporated among the standard tools of planetary protection (PP) and could be validated for incorporation by 2026. To address the feasibility of applying modern molecular techniques to such an application, NASA conducted a technology workshop with private industry partners, academics, and government agency stakeholders, along with NASA staff and contractors. The technical discussions and presentations of the Multi-Mission Metagenomics Technology Development Workshop focused on modernizing and supplementing the current PP assays. The goals of the workshop were to assess the state of metagenomics and other advanced molecular techniques in the context of providing a validated framework to supplement the bacterial endospore-based NASA Standard Assay and to identify knowledge and technology gaps. In particular, workshop participants were tasked with discussing metagenomics as a stand-alone technology to provide rapid and comprehensive analysis of total nucleic acids and viable microorganisms on spacecraft surfaces, thereby allowing for the development of tailored and cost-effective microbial reduction plans for each hardware item on a spacecraft. Workshop participants recommended metagenomics approaches as the only data source that can adequately feed into quantitative microbial risk assessment models for evaluating the risk of forward (exploring extraterrestrial planet) and back (Earth harmful biological) contamination. Participants were unanimous that a metagenomics workflow, in tandem with rapid targeted quantitative (digital) PCR, represents a revolutionary advance over existing methods for the assessment of microbial bioburden on spacecraft surfaces. The workshop highlighted low biomass sampling, reagent contamination, and inconsistent bioinformatics data analysis as key areas for technology development. Finally, it was concluded that implementing metagenomics as an additional workflow for addressing concerns of NASA's robotic mission will represent a dramatic improvement in technology advancement for PP and will benefit future missions where mission success is affected by backward and forward contamination.


Assuntos
Planetas , Voo Espacial , Estados Unidos , Humanos , Meio Ambiente Extraterreno , Metagenômica , United States National Aeronautics and Space Administration , Astronave , Políticas
11.
Life Sci Space Res (Amst) ; 37: 7-14, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37087181

RESUMO

Since the advent of space exploration missions, various space agencies have been working to improve the quality of food and nutrition for crew members. Food processing, preservation, and packaging have evolved with the advancement of technology. Most of the food available on earth can be consumed in space by changing its form. Shelf life and food acceptability can be enhanced by using suitable packaging materials. Here we review space food, which has been categorized into bite-size food, rehydratable food, thermostabilized food, intermediate moisture food, and irradiated food. Additionally, packaging materials and different packaging forms for space food are reviewed. Finally, the review highlights the challenges in space food packaging and food packaging trends of the Defence research and development organization (DRDO), the Japan aerospace exploration agency (JAXA), and the National aeronautics and space administration (NASA).


Assuntos
Embalagem de Alimentos , Voo Espacial , Estados Unidos , Alimentos , Manipulação de Alimentos , Estado Nutricional , Astronautas , United States National Aeronautics and Space Administration
12.
Surg Endosc ; 37(7): 5077-5085, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-36917343

RESUMO

OBJECTIVE: The objective of the study was to assess the validity of the NASA-TLX score in rating the workload of pediatric robotic operations. METHODS: The workload of 230 pediatric gastrointestinal and thoracic robotic operations was rated using the NASA-TLX score. The difference between the high workload group and the low workload group in each subscale of the NASA-TLX score was analyzed. The correlation of each subscale with the total workload score in the high workload group and low workload group was also analyzed. A logistic regression analysis was subsequently conducted to assess the effects of different factors (sex, age, weight, procedure duration, procedure specialties, combined malformation and blood loss) on the workload. RESULTS: The average NASA-TLX score was 56.5 ± 5.1 for the total group, 56.9 ± 5.0 for the gastrointestinal group and 54.6 ± 4.8 for the thoracic group, p = 0.007. The score of the high workload group was 62.7 ± 3.2, while it was 50.6 ± 2.7 for the low workload group (p < 0.001). The score on each subscale was also significantly different between the high and low workload groups. In the high workload group, a stronger correlation was observed between the total score and TD and Fr and a lower correlation with MD and Pe. In the low workload group, all six subscales showed a moderate correlation with the total score. A multivariate logistic regression analysis revealed that the procedure duration was an independent influencing factor for a higher workload score. CONCLUSIONS: NASA-TLX is a valid tool to rate the surgeon's workload in pediatric robotic surgery. A longer operative time contributes to a higher workload.


Assuntos
Procedimentos Cirúrgicos Robóticos , Especialidades Cirúrgicas , Estados Unidos , Humanos , Criança , Carga de Trabalho , United States National Aeronautics and Space Administration , Inquéritos e Questionários , Análise e Desempenho de Tarefas
13.
Br J Hist Sci ; 56(2): 247-267, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36776108

RESUMO

On 16 September 1987, the main chlorofluorocarbon-producing and -consuming countries signed the Montreal Protocol, despite the absence of a scientific consensus on the mechanisms of ozone depletion over Antarctica. We argue in this article that the rapid diffusion from late 1985 onwards of satellite images showing the Antarctic ozone hole played a significant role in this diplomatic outcome. Whereas negotiators claimed that they chose to deliberately ignore the Antarctic ozone hole during the negotiations since no theory was able yet to explain it, the images still loomed large for many of the actors involved. In Western countries, the National Aeronautics and Space Administration's (NASA) satellite visualizations were diffused through the general press and television stations. Other popular and mass media outlets followed quickly. In describing the circulation and appropriation processes of these images within and beyond the scientific and negotiation arenas, we show that the ozone hole images did play an important part in ozone diplomacy in the two years leading up to the signing of the Montreal Protocol, both in the expert and diplomatic arenas and as public diplomacy tools. We conclude by encouraging scholars to engage with new visual archives and to contribute to the development of the vibrant new field of research on visual diplomacy.


Assuntos
Diplomacia , Perda de Ozônio , Ozônio , Estados Unidos , Negociação , United States National Aeronautics and Space Administration , Ozônio/análise
15.
Environ Sci Pollut Res Int ; 30(15): 43619-43640, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36662434

RESUMO

Drought directly impacts the human economy and society, so a proper understanding of its spatiotemporal characteristics in different time scales and return periods can be effective in its evaluation and risk warning. In this research, the spatiotemporal variation of drought characteristics in 70 investigated stations in Iran during 1981-2020 was examined, evaluated, and compared. The Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) have been used on time scales of 1, 3, 6, 9, 12, and 24 months to calculate the meteorological drought. Drought characteristics have been calculated through the run theory method, and the correlation between these characteristics has been checked. Statistical distribution functions have been used to calculate drought characteristics for the 10-, 20-, 50-, and 100-year return periods. Results show that the duration, severity, and peak of the drought in rainy areas increase as the return period increases. The drought features obtained from the SPI and SPEI show that the average value of severity obtained based on the SPI (43.5) is higher than that of the SPEI (40.9) while the average values of the peak are 3.9 and 2.6 for SPI and SPEI, respectively. Extreme drought was identified in 1990 in all regions of Iran. The highest severity in the current study is from 1999 to 2003. At the end of this period, Iran faced wet years. These results are evident on all time scales. The results obtained in this study can identify drought-prone regions and the beneficial use of water resources in the region.


Assuntos
Secas , United States National Aeronautics and Space Administration , Estados Unidos , Humanos , Irã (Geográfico) , Meteorologia , Chuva
16.
Life Sci Space Res (Amst) ; 36: 90-104, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36682835

RESUMO

For missions beyond low Earth orbit to the moon or Mars, space explorers will encounter a complex radiation field composed of various ion species with a broad range of energies. Such missions pose significant radiation protection challenges that need to be solved in order to minimize exposures and associated health risks. An innovative galactic cosmic ray simulator (GCRsim) was recently developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). The GCRsim technology is intended to represent major components of the space radiation environment in a ground analog laboratory setting where it can be used to improve understanding of biological risks and serve as a testbed for countermeasure development and validation. The current GCRsim consists of 33 energetic ion beams that collectively simulate the primary and secondary GCR field encountered by humans in space over the broad range of particle types, energies, and linear energy transfer (LET) of interest to health effects. A virtual workshop was held in December 2020 to assess the status of the NASA baseline GCRsim. Workshop attendees examined various aspects of simulator design, with a particular emphasis on beam selection strategies. Experimental results, modeling approaches, areas of consensus, and questions of concern were also discussed in detail. This report includes a summary of the GCRsim workshop and a description of the current status of the GCRsim. This information is important for future advancements and applications in space radiobiology.


Assuntos
Radiação Cósmica , Proteção Radiológica , Voo Espacial , Estados Unidos , Humanos , United States National Aeronautics and Space Administration , Radiobiologia , Carmustina
18.
Science ; 379(6628): 123-124, 2023 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-36634175

RESUMO

Agency lays out initial plan for multibillion-dollar Habitable Worlds Observatory.


Assuntos
Exobiologia , Meio Ambiente Extraterreno , Estados Unidos , United States National Aeronautics and Space Administration
19.
Work ; 75(4): 1265-1275, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36710696

RESUMO

BACKGROUND: Today's work environments have high cognitive demands, and mental workload is one of the main causes of work stress, human errors, and accidents. While several mental workload studies have compared the mental workload perceived by groups of experienced participants to that perceived by novice groups, no comparisons have been made between the same individuals performing the same tasks at different times. OBJECTIVE: This work aims to compare NASA Task Load Index (NASA-TLX) to Workload Profile (WP) in terms of their sensitivity. The comparison considers the impact of experience and task differentiation in the same individual once a degree of experience has been developed in the execution of the same tasks. It also considers the acceptability and intrusivity of the techniques. METHODS: The sample consisted of 30 participants who performed four tasks in two sessions. The first session was performed when participants had no experience; the second session was performed after a time of practice. Mental workload was assessed after each session. Statistical methods were used to compare the results. RESULTS: The NASA-TLX proved to be more sensitive to experience, while the WP showed greater sensitivity to task differentiation. In addition, while both techniques featured a similar degree of intrusivity, the NASA-TLX received greater acceptability. CONCLUSION: The acceptability of WP is low due to the high complexity of its dimensions and clarifying explanations of these may be necessary to increase acceptability. Future research proposals should be expanded to consider mental workload when designing work environments in current manufacturing environments.


Assuntos
Estresse Ocupacional , Análise e Desempenho de Tarefas , Estados Unidos , Humanos , United States National Aeronautics and Space Administration , Carga de Trabalho/psicologia
20.
J Dairy Sci ; 106(2): 1142-1158, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36567248

RESUMO

Weather station data and test-day production records can be combined to quantify the effects of heat stress on production traits in dairy cattle. However, meteorological data sets that are retrieved from ground-based weather stations can be limited by spatial and temporal data gaps. The National Aeronautics and Space Administration Prediction of Worldwide Energy Resources (NASA POWER) database provides meteorological data over regions where surface measurements are sparse or nonexistent. The first aim of this study was to determine whether NASA POWER data are a viable alternative resource of weather data for studying heat stress in Canadian Holsteins. The results showed that average, minima, and maxima ambient temperature and dewpoint temperature as well as 4 different types of temperature-humidity index (THI) values from NASA POWER were highly correlated to the corresponding values from weather stations (regression R2 > 0.80). However, the NASA POWER values for the daily average, minima, and maxima wind speed and relative humidity were poorly correlated to the corresponding weather station values (regression R2 = 0.10 to 0.49). The second aim of this study was to quantify the influence of heat stress on Canadian dairy cattle. This was achieved by determining the THI values at which milk, protein, and fat yield started to decline due to heat stress as well as the rates of decline in these traits after the respective thresholds, using segmented polynomial regression models. This was completed for both primiparous and multiparous cows from 5 regions in Canada (Ontario, Quebec, British Columbia, the Prairies, and the Atlantic Maritime). The results showed that all production traits were negatively affected by heat stress and that the patterns of responses for milk, fat, and protein yields to increasing THI differed from each other. We found 3 THI thresholds for milk yield, 1 for fat yield, and 2 for protein yield. All thresholds marked a change in rate of decrease in production yield per unit THI, except for the first milk yield threshold, which marked a greater rate of increase. The first thresholds for milk yield ranged between 47 and 50, the second thresholds ranged between 61 and 69, and the third thresholds ranged between 72 and 76 THI units. The single THI threshold for fat yield ranged between 48 and 55 THI units. Finally, the first and second thresholds ranged between 58 and 62 THI units and 72 and 73 THI units for protein yield, respectively.


Assuntos
Doenças dos Bovinos , Transtornos de Estresse por Calor , Estados Unidos , Gravidez , Feminino , Bovinos , Animais , Lactação/fisiologia , United States National Aeronautics and Space Administration , Leite/metabolismo , Resposta ao Choque Térmico/fisiologia , Umidade , Transtornos de Estresse por Calor/veterinária , Colúmbia Britânica , Temperatura Alta , Doenças dos Bovinos/metabolismo
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