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Title: Physiological parameters for thermal stress in dairy cattle
Authors: Dalcin, Vanessa Calderaro
Fischer, Vivian
Daltro, Darlene dos Santos
Alfonzo, Evelyn Priscila München
Stumpf, Marcelo Tempel
Kolling, Giovani Jacob
Silva, Marcos Vinícius Gualberto Barbosa da
Pimentel, Concepta Margaret McManus
Assunto:: Valores
Conforto térmico
Termorregulação
Issue Date: Aug-2016
Publisher: Sociedade Brasileira de Zootecnia
Citation: DALCIN, Vanessa Calderaro et al. Physiological parameters for thermal stress in dairy cattle. Revista Brasileira de Zootecnia, Viçosa, v. 45, n. 8, p. 458-465, ago. 2016. Disponível em: <http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982016000800458&lng=en&nrm=iso>. Acesso em: 21 dez. 2017. doi: http://dx.doi.org/10.1590/S1806-92902016000800006.
Abstract: The objective of this study was to investigate changes in physiological parameters of dairy cows and understand which physiological parameters show greater reliability for verification of heat stress. Blood samples were collected for analysis and included hematocrit (Ht), erythrocyte count (ERY), and hemoglobin count (HEMO). In addition, physiological variables, including rectal temperature (RT), heart rate (HR), respiratory rate (RR), and panting score (PS) were recorded in 38 lactating cows. These varied according to genetic group (1/2, 3/4, and pure bred Holstein (HO)). Analysis of variance considering the effects of genetic group, days, and their interaction as well as linear and quadratic effect of the black globe humidity index (BGHI) was performed, as well as broken-line regression. These values were higher in pure HO than in 3/4 and 1/2 groups. The average BGHI during the morning was 74, when 70, 43, and 13% of pure HO, 3/4, and 1/2, respectively, presented RR above reference value. The RR was the best indicator of heat stress and its critical value was 116 breaths/min for 1/2, 140 for 3/4, and 168 breaths/min for pure HO cows. In the HO group, physiological variables increased linearly with BGHI, without presenting inflection in the regression. The inflection point occurred at a higher BGHI for the 1/2 group compared with the other groups. Hematocrit and HEMO were different among genetic groups and did not vary with BGHI, showing that stress was not sufficient to alter these hematological parameters. The 1/2 HO group was capable of maintaining normal physiological parameters for at least 3 BGHI units above that of HO and 1 to 3 units higher than 3/4 HO for RR and RT, respectively. Respiratory rate is the physiological parameter that best predicts heat stress in dairy cattle, and the 1/2 Holstein group is the best adapted to heat stress.
Licença:: Revista Brasileira de Zootecnia - This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0). Fonte: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982016000800458&lng=en&nrm=iso. Acesso em: 21 dez. 2017.
DOI: http://dx.doi.org/10.1590/S1806-92902016000800006
Appears in Collections:CFS - Artigos publicados em periódicos

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