Contents lists available at ScienceDirect Livestock Science journal homepage: www.elsevier.com/locate/livsci Short Communication Technical note: An acoustic method for assessing the respiration rate of free- grazing dairy cattle Giovanna Araújo de Carvalho a , Ana Karina Dias Salman b, ⁎ , Pedro Gomes da Cruz b , Elaine Coimbra de Souza a , Francyelle Ruana Faria da Silva c , Eduardo Schmitt d a Postgraduate Program in Regional Development and Environment – PPGDRA, Federal University of Rondônia – UNIR, BR 364 km 9.5, Zip Code 76800-000, Porto Velho, Rondônia, Brazil b Brazilian Agricultural Research Corporation - Embrapa Rondônia, BR 364 km 5.5, Zip Code 76815-800, Porto Velho, Rondônia, Brazil c Postgraduate Program in Environmental Science – PPGCA, Federal University of Rondônia – UNIR, Av. Norte Sul, 7300, Zip Code 76940-000, Rolim de Moura, Rondônia, Brazil d Federal University of Pelotas (UFPel), Veterinary College, Zip Code 96010-900, Capão do Leão, Rio Grande do Sul, Brazil ARTICLEINFO Keywords: Thermal stress Precision livestock Method validation ABSTRACT The aim of this study was to validate whether acoustic data analysis can be used to assess respiration rate (RR) in dairy cattle under grazing systems. Two validation trials, one with heifers and other with lactating cows, were conducted. The RR derived from acoustic data acquired with an MP3 recorder fitted on the halter was compared to the RR derived from a visual method, counting flank movements. Data were analyzed using correlation test and Willmott's index of agreement (d). There was no significant difference (P>0.05) between RR assessed using the acoustic or visual method, in both heifers and lactating cows. The coefficients of determination (R 2 ) in- dicated that 92.31% (heifers) and 62.09% (lactating cows) of the variability in the RR derived using the visual assessment method was explained by the RR derived using the acoustic method. The d values were 0.99 (heifers) and 0.98 (lactating cows), which denoted good agreement between the RR derived using the two methods. The acoustic method is non-invasive, allows for the assessment of RR in free-grazing dairy cattle and may replace the current standard of visual counting. 1. Introduction Assessment of respiration rate (RR) in cattle is valuable in mon- itoring health status (Stewart et al., 2017) and detecting stress, espe- cially heat stress (Dalcin et al., 2016). To date, very little is known regarding the response of the Girolando breed to heat stress, especially in pasture-based systems. Conventionally, RR is measured by counting flank movements using a stopwatch (Atkins et al., 2018; Costa et al., 2015; Lowe et al., 2019; Milan et al., 2016). However, this method is time-consuming and la- borious (Eigenberg et al., 2000), and it is impractical to continuously measure RR. The observer could also influence animal behavior (Milan et al., 2016). Therefore, to accurately monitor RR, it is advisable to increase the frequency of observations of physiological responses. Application of robust time-series technology facilitates consistent data collection (Eigenberg et al., 2000). Automated RR equipment has been developed (Atkins et al., 2018; Lowe et al., 2019; Milan et al., 2016; Stewart et al., 2017; Strutzke et al., 2019), but requires data processing algorithms and internet connectivity to function adequately. We wanted to further examine, if it could be used to measure RR of these cattle under heat stress conditions. The aim of our study was to validate a new acoustic method of RR assessment in free-grazing dairy cattle, in comparison with the conventional visual method. 2. Material and Methods All procedures involving animal care and handling were approved by the Ethics Committee in Animal Utilization (CEUA) of Embrapa Rondônia (protocol number 01-2018). The validation study was conducted at the Embrapa Rondônia's https://doi.org/10.1016/j.livsci.2020.104270 Received 23 January 2020; Received in revised form 14 August 2020; Accepted 22 September 2020 ⁎ Corresponding author. E-mail addresses: giovanna.carvalhozootec@gmail.com (G.A. de Carvalho), ana.salman@embrapa.br (A.K.D. Salman), pedro-gomes.cruz@embrapa.br (P.G. da Cruz), lainezootec@gmail.com (E.C. de Souza), franruana@gmail.com (F.R.F. da Silva), schmitt.edu@gmail.com (E. Schmitt). URL: http://orcid.org/0000-0001-6594-0667 (A.K.D. Salman). Livestock Science 241 (2020) 104270 Available online 23 September 2020 1871-1413/ © 2020 Elsevier B.V. All rights reserved. T