Índices de Estresse Térmico para Vacas Leiteiras em Regiões Equatoriais Secas

Silva, Alexandre Rodrigues; Morais, Débora Andréia Evangelista Façanha; Guilhermino, Magda Maria; LaScala, Newton; Maia, Alex Sandro Campos

doi:10.15528/2176-4158/rcpa.v12n2p125-128

Cited by 2 publications

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“…Assim como neste estudo, FAÇANHA et al ( 2016) também observaram variação nas condições climáticas entre diferentes épocas do ano (seca e chuvosa) e entre os horários do dia (manhã e tarde), refletindo em maior aquecimento corporal dos animais e alteração nos parâmetros fisiológicos. SILVA et al (2010) observaram valores superiores de temperatura de superfície corporal para vacas Jersey e Holandesas mantidas em região quente. A TSC dos animais variou de 34,0 a 41,2 °C.…”

Section: Resultsunclassified

Impacto do microclima sobre a fisiologia, pelame e produção de leite de vacas lactantes em diferentes estações do ano

Santos

Carvalho

Ruas

et al. 2018

Rev. Cienc. Agrovet.

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Section: Resultsunclassified

Impacto do microclima sobre a fisiologia, pelame e produção de leite de vacas lactantes em diferentes estações do ano

Santos

Carvalho

Ruas

et al. 2018

Rev. Cienc. Agrovet.

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show abstract

“…Por equações específicas (Tabela 1), foram calculadas a radiação solar [25], a umidade relativa [23], a temperatura radiante média [23] e os principais índices de estresse térmico selecionados da literatura: Índice de Temperatura e Umidade [30], Índice de Globo Negro e Umidade [4], Índice de Temperatura Equivalente [2], Índice de Estresse Ambiental [18], Índice de Frequência Respiratória (para temperatura ambiente superior a 25ºC) [7,8], Índice de Carga Térmica (para temperatura de globo negro superior a 25ºC) [11], Índice de Especificação Ambiental [26], Índice Climático Compreensivo [14], Índice de Con-forto Térmico para Bovinos de Leite [29] e o Índice de Estresse Térmico para Vacas [24].…”

Section: Avaliação Do Ambiente Térmicounclassified

Most Appropriate Heat Stress Index for Half-blood Dairy Heifers

Brettas

Nascimento

Guimarães

et al. 2017

Acta Scientiae. Vet.

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Background: Heat stress indexes integrate several variables of the thermal environment in a single figure and predict their impact on animal welfare and performance. The correct interpretation of these indexes is of help in the choice of more adequate measures to attenuate the stress caused by the heat. Therefore, the aim of this research is to examine some of the heat stress indexes mentioned in the literature and to decide which ones best reflect the potential impact of meteorological conditions on the thermal homeostasis of half-blood dairy heifers bred in Uberlândia, Triângulo Mineiro area, Minas Gerais, Brazil.Materials, Methods & Results: Eight half-blood dairy heifers were exposed to direct sunlight from 9 h to 13 h in the months of November and December of 2016, and also January and February of 2017, 5 days per month on average, in Uberlândia, MG, Brazil. After this challenge, the respiratory rate and the rectal temperature were measured. Simultaneously to the collection of physiological variables, the temperatures of dry bulb and wet bulb, as well as that of black globe, were quantified, as was the wind speed. Afterwards, the solar radiation, the relative humidity, the mean radiant temperature and some heat stress indexes were calculated, the latter being Temperature-Humidity Index, Black Globe-Humidity Index, Equivalent Temperature Index, Environmental Stress Index, Respiratory Rate Index, Thermal Load Index, Environmental Specification Index, Thermal Comfort Index for Dairy Cattle, Comprehensive Climate Index and Cattle Heat Stress Index. These indexes were, then, correlated with the physiological variables. The averages of room temperature, black globe temperature, solar radiation, wind speed, radiant temperature and relative humidity were, respectively, 29.96°C, 41.73°C, 831.02 W/m2, 0.11 m/s-1, 318.14 K and 50.51%. Rectal temperature averaged 38.8ºC while respiratory rate averaged 41.97 breaths per minute-1. Correlating the 10 heat stress indexes with these two physiological variables, it was verified that the highest values, with a confidence of 95%, were demonstrated by the Equivalent Temperature Index (0.200 and 0.317, respectively), followed by the Cattle Heat Stress Index (0.186 and 0.314, respectively).Discussion: Room temperature was within the thermoneutral zone for half-blood dairy cattle. Nevertheless, the mean radiant temperature and the black globe temperature were higher, due to intense solar radiation. Wind speed was not very expressive and relative humidity was close to what was required. The average values of rectal temperature and respiratory rate were normal, which indicated the heifers are adapted to the thermal environment. Regarding the heat stress indexes, the Equivalent Temperature Index was recommended, as it presented the highest amount of meaningful correlations with the physiological variables, followed by the Cattle Heat Stress Index and the Environmental Stress Index. The average value of the Equivalent Temperature Index remained in the “caution” category, according to the literature’s two existing scales for interpretation of said index’s results, indicating the occurrence of stress by heat, albeit not severe. In conclusion, the Equivalent Temperature Index is considered the most appropriate heat stress index for evaluating a heat stress situation in half-blood dairy heifers bred in Uberlândia, Triângulo Mineiro, followed by the Cattle Heat Stress Index and the Environmental Stress Index.

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Índices de Estresse Térmico para Vacas Leiteiras em Regiões Equatoriais Secas

Cited by 2 publications

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Impacto do microclima sobre a fisiologia, pelame e produção de leite de vacas lactantes em diferentes estações do ano

Impacto do microclima sobre a fisiologia, pelame e produção de leite de vacas lactantes em diferentes estações do ano

Most Appropriate Heat Stress Index for Half-blood Dairy Heifers

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