Regulation of Acclimation to Environmental Stress

Roy, K. S.; Collier, Robert J.

doi:10.1002/9781119949091.ch4

Cited by 17 publications

(15 citation statements)

References 63 publications

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“…Bos indicus cattle evolved in tropical regions, with high TA and RH, and as a result these breeds of cattle have a number of genetic differences that support thermotolerance (Hansen, 2004;Roy and Collier, 2012). Therefore the survivability of Bos indicus breeds in tropical environments arises from the adaptations developed throughout successive generations.…”

Section: Adaptation and Acclimationmentioning

confidence: 99%

“…Heat shock induced by hot weather conditions acutely decreases DNA synthesis and negatively affects the ability of the cells to maintain their cytoskeleton, resulting in a collapse to the cells structure (Roy and Collier, 2012). Induction, regulation and transcription of HSP are facilitated by the interaction of heat shock factor transcription factors (Pockley, 2003).…”

Section: In Temperature Shockedmentioning

confidence: 99%

“…Furthermore knowledge regarding the initiation and role of HSP within the heat load response is not yet fully understood. Roy and Collier (2012) indicated that the ability of an animal to tolerate thermal challenges at the cellular level is a direct function of their ability to maintain elevated levels of circulating HSP. However Lindquist and Craig (1988) indicated that there are circumstances where exposure to heat load does not correlate with the initiation of the HSP response.…”

Section: Heat Shock Protein 70mentioning

confidence: 99%

“…Adaptation, however, refers to the biological change in successive generations by favouring genetic selection within a population due to continuous stressor exposure that supports species survival (Roy and Collier, 2012). Bos indicus cattle evolved in tropical regions, with high TA and RH, and as a result these breeds of cattle have a number of genetic differences that support thermotolerance (Hansen, 2004;Roy and Collier, 2012).…”

Section: Adaptation and Acclimationmentioning

confidence: 99%

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Biological responses of feedlot cattle to heat load

Lees¹

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Heat load is a significant animal welfare and cost of production issue worldwide. In the US alone heat load is reported to have an annual economic burden of > $300 million in the beef sector.Furthermore animal growth is often depressed during summer resulting in heat related decreases in weight gain of approximately 10 kg which coincides with a 7 day increase in days on feed. The reduced growth rate increases days on feed, thereby increasing the cost of production. Whilst the effects of heat load on cattle has been researched for a number of years, there is speculation as to the interactions between hot environmental conditions and livestock performance, reproduction, health and overall wellbeing. Therefore there is a need to develop a more comprehensive understanding of the dynamic responses of animals to heat load. The key focus of heat load research is to develop effective management strategies to support animal comfort and performance during hot periods.While heat load can occur in pasture raised cattle, it is mostly observed within the intensive grain feed feedlot industry. Heat load occurs where a combination of environmental conditions exceed the animals ability to regulate body temperature, thus impacting on homeostasis. However how an animal responds to heat load is also dependent on a number of individual characteristics, including genotype, coat characteristics, health status and days on feed. Therefore no two animals will respond to hot climatic conditions in exactly the same manner. There are numerous responses to heat load that can be measured and/or observed in cattle, including changes in behaviour, respiratory dynamics, blood metabolites and body temperature. The experiments within this thesis were focused on investigating the; A key aspect in managing heat load is that feedlot personnel are able to recognise the responses of cattle to high heat load. Improvements in animal management have contributed to alleviating some of the negative effects of heat load. However summer conditions are still responsible for significant production losses and welfare concerns worldwide. Furthermore heat load cannot be completely eradicated where there are animal production operations in tropical and sub-tropical regions.Therefore the primary purpose of heat load research becomes focused on the effective use of mitigation strategies prior to and during heat related stress events, thus improving animal survivability and welfare during these events.iii Declaration by author Publications included in this thesisNo publications included. Contributions by others to the thesis

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Section: Adaptation and Acclimationmentioning

confidence: 99%

Section: In Temperature Shockedmentioning

confidence: 99%

Section: Heat Shock Protein 70mentioning

confidence: 99%

Section: Adaptation and Acclimationmentioning

confidence: 99%

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Biological responses of feedlot cattle to heat load

Lees¹

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“…-Adaptation, however, refers to the biological change in successive generations by favouring genetic selection within a population due to continuous stressor exposure that supports species survival (Roy and Collier, 2012).…”

Section: Future Directionsmentioning

confidence: 99%

A heat load index for dairy cattle

Lees¹

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Summer is often associated with a decrease in production animal performance. This is particularly evident in dairy cows; where decreases in milk yields, conception rates, and changes in milk composition have been recorded for many years. For the US dairy industry, heat load has an annual economic burden between $ 897 and $ 1 500 million. In Australia, the cost of heat stress has been reported as approximately $ 11 986 per year for a 100 cow herd, averaging 25 litres per cow without access to shade. It is difficult to completely quantify the economic losses associated with heat load due to the interactions of heat load with feed intake; milk production and composition; and reproduction. Beyond this, high heat load (environmental and metabolic) can have a negative effect on cow welfare and wellbeing. In the tropics and sub-tropics summer conditions are of further concern. In these regions, dairy cows may be subjected to hot weather conditions outside their thermoneutral zone for considerable periods of time.Determining the effect of heat load on cattle has led to the development of a number of climatic indices. These models use ambient weather conditions to describe the effect they will have on the production and/or welfare of animals. The Temperature Humidity Index (THI) is the model currently used in the Australian dairy industry. It utilises measures of ambient temperature (TA, °C) and relative humidity (RH) to produce a unit value that describes the effect of the thermal environment on the cow. However it has been highlighted that air movement and solar load affect thermal exchange mechanisms, thus influencing the heat load status of dairy cows. Given that the THI does not incorporate the effects of air movement or solar radiation on cows, there is the potential that the model may not adequately describe the effects of heat load on dairy cows.To date, there has not been a heat load model developed specifically for dairy cows housed outside in a sub-tropical environment that takes into account these parameters, and the associated effects on production efficiency. Therefore the experiments described within this thesis were to define the; Where BGT = black globe temperature (°C); and RH = relative humidity (decimal)Improvements in animal management have contributed to alleviating some of the negative effects of heat load. However summer conditions are still responsible for significant production losses and welfare concerns worldwide. Furthermore heat load cannot be completely eradicated where there are animal production operations in tropical and sub-tropical regions. Thus the ability to forecast and predict heat load conditions becomes integral to implementing effective mitigation strategies.Traditionally the THI has been defined as the gold standard in identifying the intensity of the thermal environment on lactating dairy cows, however the THI does not incorporate wind speed (WS, m/s) or solar radiation (SR; W/m 2 ), which are well known to influence thermal exchange mechanisms.The purpose of this thes...

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Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

Scharf

2012

Journal of Thermal Biology

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Regulation of Acclimation to Environmental Stress

Cited by 17 publications

References 63 publications

Biological responses of feedlot cattle to heat load

Biological responses of feedlot cattle to heat load

A heat load index for dairy cattle

Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

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