Environmental factors influencing heat stress in feedlot cattle1,2

Mader, Terry L.; Davis, Michael S.; Brown–Brandl, T. M.

doi:10.2527/2006.843712x

Cited by 693 publications

(613 citation statements)

References 15 publications

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“…The variability was in the length of acclimation period and ranged from 9 days for Angus and Charolais to 14 days for Polled Hereford (Hereford and Santa Gertrudis had intermediate values (12 days)). In a recent study, Brown-Brandl et al (2006) reported a significant effect of breed and breed by temperature interaction on respiration rates and panting scores. Angus and MARC III breeds had the highest respiration rate and panting score, followed by Gelbvieh and then Charolais.…”

Section: Heat Stress Critical Temperatures and Bioclimatic Indicesmentioning

confidence: 96%

“…Beef cattle are particularly vulnerable not only to extreme environmental conditions but also to rapid changes in climate. In particular, fatter cattle (subcutaneous fat acts like insulation and slows heat dissipation), cattle with a heavy hair coat (more insulation) and darker-coated animals (black and dark red cattle) are very sensitive to heat (Brown-Brandl et al, 2006;Gaughan et al, 2009b). The Scientific Committee on Animal Figure 5 Effects of heat stress (HS) or pair-feeding (PF) on (a) dry matter intake and (b) milk yield in lactating Holstein cows.…”

Section: Reproductionmentioning

confidence: 99%

“…In terms of adaptation measures, it is generally faster to improve welfare, production and reproduction performances by altering the environment (West, 2003;Mader et al, 2006). However, intense environmental modification (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Metabolic and hormonal acclimation to heat stress in domesticated ruminants

Bernabucci

Lacetera

Baumgard

et al. 2010

Animal

738

492

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Environmentally induced periods of heat stress decrease productivity with devastating economic consequences to global animal agriculture. Heat stress can be defined as a physiological condition when the core body temperature of a given species exceeds its range specified for normal activity, which results from a total heat load (internal production and environment) exceeding the capacity for heat dissipation and this prompts physiological and behavioral responses to reduce the strain. The ability of ruminants to regulate body temperature is species-and breed-dependent. Dairy breeds are typically more sensitive to heat stress than meat breeds, and higher-producing animals are more susceptible to heat stress because they generate more metabolic heat. During heat stress, ruminants, like other homeothermic animals, increase avenues of heat loss and reduce heat production in an attempt to maintain euthermia. The immediate responses to heat load are increased respiration rates, decreased feed intake and increased water intake. Acclimatization is a process by which animals adapt to environmental conditions and engage behavioral, hormonal and metabolic changes that are characteristics of either acclimatory homeostasis or homeorhetic mechanisms used by the animals to survive in a new 'physiological state'. For example, alterations in the hormonal profile are mainly characterized by a decline and increase in anabolic and catabolic hormones, respectively. The response to heat load and the heat-induced change in homeorhetic modifiers alters post-absorptive energy, lipid and protein metabolism, impairs liver function, causes oxidative stress, jeopardizes the immune response and decreases reproductive performance. These physiological modifications alter nutrient partitioning and may prevent heat-stressed lactating cows from recruiting glucose-sparing mechanisms (despite the reduced nutrient intake). This might explain, in large part, why decreased feed intake only accounts for a minor portion of the reduced milk yield from environmentally induced hyperthermic cows. How these metabolic changes are initiated and regulated is not known. It also remains unclear how these changes differ between short-term v. long-term heat acclimation to impact animal productivity and well-being. A better understanding of the adaptations enlisted by ruminants during heat stress is necessary to enhance the likelihood of developing strategies to simultaneously improve heat tolerance and increase productivity.Keywords: ruminants, heat stress, metabolism, acclimation, adaptation ImplicationsHeat stress is a significant financial burden to animal agriculture in most areas of the world. Acclimation to heat stress imposes behavioral, physiological and metabolic adjustments to reduce the strain and enhances the likelihood of surviving the stress, and it also frequently reduces ruminant performance and compromises health. Improving our knowledge of physiological and metabolic mechanisms of acclimation may contribute to the development and adoption of proce...

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Section: Heat Stress Critical Temperatures and Bioclimatic Indicesmentioning

confidence: 96%

Section: Reproductionmentioning

confidence: 99%

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Metabolic and hormonal acclimation to heat stress in domesticated ruminants

Bernabucci

Lacetera

Baumgard

et al. 2010

Animal

738

492

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“…The panting score (PS) is an example of the latter and is based on visual evaluation of the presence and degree of two important heat stress signs in cattle, panting and drooling (Mader et al, 2006 andSchütz et al 2014). The score varies between 0 (no panting or drooling) and 4.5 (extreme panting and drooling).…”

Section: Introductionmentioning

confidence: 99%

“…Proactive planning of cattle handling and management based on weather-predictions, requires antecedent validation of climatic heat stress indices and associated heat stress thresholds (Table 1). Not all heat stress thresholds have been validated based on animal-based measures, but the more recent climatic indices, such as the heat load index (HLI; Gaughan et al, 2008), an adjusted version of the temperature humidity index (Mader et al, 2006) and the comprehensive climatic index (Mader et al, 2010) do have validated heat stress thresholds (Table 1). In addition, Gaughan et al (2010b) compared the tolerance to increasing HLI values, based on increasing PS, for several (n = 17 total) Bos indicus, Bos taurus and B. indicus × B. taurus feedlot steers, during summertime in Australia, which is characterised by a warm climate.…”

Section: Introductionmentioning

confidence: 99%

Effect of summer conditions and shade on behavioural indicators of thermal discomfort in Holstein dairy and Belgian Blue beef cattle on pasture

laer¹,

Moons

Ampe³

et al. 2015

Animal

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Using behavioural indicators of thermal discomfort, that is, shade seeking, panting scores (PS) and respiration rate (RR), we evaluated the effect of hot summer conditions and shade, for a herd of adult Holstein dairy cows and a herd of Belgian Blue beef cows kept on pasture in a temperate area (Belgium). During the summer of 2012, both herds were kept on pasture without access to shade (NS). During the summers of 2011 and 2013 each herd was divided into one group with (S) and one without (NS) access to shade. Shade was provided by young trees with shade cloth (80% reduction in solar radiation) hung between them. For S cows, we investigated how shade use was related to hot conditions as quantified by six climatic indices. The heat load index (HLI), which incorporates air temperature and humidity, solar radiation and wind speed, was the best predictor of the six indices tested. In 2011, there was a relatively high threshold for use of shade. When HLI = 90, shade use probability reached 17% for dairy cows and 27% for beef cows. In 2013, however, at HLI = 90, shade use probability reached 48% for dairy cows and 41% for beef cows. For animals from the NS treatment we determined the effect of hot summer conditions on RR and PS (with 0 = no panting and 4.5 = extreme panting). In both types of cattle, an increase in black globe temperature was the best predictor for increasing RR and PS. Furthermore, we determined how the effect of hot summer conditions on RR and PS was affected by the use of shade. Under hot conditions (black globe temperature ⩾ 30°C), >50% of the animals under shade retained normal PS and RR (PS < 1 and RR < 90 breaths per minute), whereas normal RR and PS were significantly less prevalent for animals outside shade. Our findings suggest that, even in temperate summers, heat can induce thermal discomfort in cattle, as evidenced by increases in shade use, RR and PS, and that shade increases thermal comfort.

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