Flight speed as an indicator of Zebu cattle growth performance and suitability to the feedlot environment Désirée Gellatly A , Joslaine N. S. G. Cyrillo B , Aline C. Sant’Anna C , Tiago S. Valente D,E , Karen Schwartzkopf-Genswein A and Mateus J. R. Paranhos da Costa E,F A Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada. B Centro APTA Bovinos de Corte, Instituto de Zootecnia, Sertãozinho, SP 14.160-970, Brazil. C Universidade Federal de Juiz de Fora, Departamento de Zoologia, Juiz de Fora, MG 36.036-900, Brazil. D University of Alberta, Department of Agricultural, Life and Environmental Sciences, Faculty of Agricultural Food and Nutritional Science, 410 Agriculture/Forestry Centre, Edmonton, Alberta, T6G 2P5, Canada. E UNESP, Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Zootecnia, Pesquisador CNPq, 14.884-900 Jaboticabal, SP, Brazil. F Corresponding author. Email: mateus.paranhos@unesp.br Abstract Context. Studies assessing the relationship between cattle reactivity and growth performance, as well as suitability to the feedlot, in Zebu cattle are limited. Based on previous studies using Bos Taurus cattle, it is expected that reactivity measured at weaning could be used as a predictor of feedlot performance, and that cattle with greater flight speed (FS) would have reduced average daily gain (ADG). Aims. The aims of this study were to (1) determine if FS (m/s) measured before entry into the feedlot could be used as a predictor of cattle performance, (2) evaluate the consistency of FS over time, and (3) determine when FS should be measured to best predict animal suitability to the feedlot. Methods. A total of 54 Nellore and 40 Guzerat calves were assessed by using FS, which was collected at the time of (FS 0 ) and 1 week after weaning (FS 1 ), as well as on Day 28 (FS 28 ), 56 (FS 56 ) and 168 (FS 168 ) after entry into the feedlot, and a FS average was calculated using FS 28 , FS 56 and FS 168 (FS 28–168 ). Performance using ADG (kg/calf.day) was calculated for each animal over three periods: ADG 1–28 , ADG 28–168 and ADG 1–168 . Bunk attendance (min/calf.day) was recorded over a 173-day feeding period. Key results. The ADG 28–168 was reduced by 0.14 kg/calf.day for each unit increase in FS 0 (P < 0.05). Both ADG 28–168 and ADG 1–168 were reduced by 0.02 kg/calf.day for each unit increase in FS 1 (P  0.01), but neither FS 0 nor FS 1 was associated with ADG 1–28 (P > 0.10). A significant increase was observed between FS 1 and FS 28 (P < 0.01), followed by a reduction in FS 56 (P < 0.01) and FS 168 (P < 0.01). Conclusion. FS measured at or within 1 week of weaning has the potential to be used as an indicator of feedlot growth performance in Nellore and Guzerat cattle. Implications. Although our results do not indicate the efficacy of FS as a predictor of early suitability of cattle to the feedlot, it does have the potential to support its recommendation as an indicator of overall feedlot growth performance in Nellore and Guzerat breeds. Additional keywords: animal behaviour, Bos indicus, habituation, temperament. Received 3 August 2017, accepted 30 June 2019, published online 3 February 2020 Introduction Temperament has been considered a complex concept, defined by Réale et al.(2007) as ‘individual behavioural differences that are repeatable over time and across situations’. The flight speed (FS) test, developed by Burrow et al.(1988), has been widely used to assess individual variation in cattle reactivity as a proxy for animal temperament. This is one of the most reliable and validated methods to evaluate cattle temperament in the scientific literature (Burrow and Dillon 1997; Curley Jr et al. 2006; Müller and von Keyserlingk 2006; Cafe et al. 2011; Sant’Anna et al. 2012; Francisco et al. 2015; Valente et al. 2017). Studies have shown that cattle with greater FS (more excitable temperament) spend less time at the bunk consuming feed and have lower DM intake (Cafe et al. 2011), as well as lower feed efficiency (Petherick et al. 2002; Nkrumah et al. 2007; Francisco et al. 2015), weight gain (Petherick et al. 2002; Cafe et al. 2011; CSIRO PUBLISHING Animal Production Science, 2020, 60, 560–566 https://doi.org/10.1071/AN18785 Journal compilation Ó CSIRO 2020 www.publish.csiro.au/journals/an