ANIMAL WELL-BEING AND BEHAVIOR Associations between carcass weight uniformity and production measures on farm and at slaughter in commercial broiler flocks Guro Vasdal, *, 1 Erik Georg Granquist, † Eystein Skjerve, † Ingrid C. de Jong, ‡ Charlotte Berg, § Virginie Michel, # and Randi Oppermann Moe † * Animalia - Norwegian Meat and Poultry Research Centre, Lorenveien 38, 0515 Oslo, Norway; † Norwegian University of Life Sciences, Faculty of Veterinary Medicine, Department of Production Animal Clinical Sciences, PO Box 8146 dep., 0033 Oslo, Norway; ‡ Wageningen University and Research, Wageningen Livestock Research, PO Box 338, 6700 AH Wageningen, The Netherlands; § Swedish University of Agricultural Sciences, Department of Animal Environment and Health, PO Box 234, 532 23 Skara, Sweden; and # French agency for food environmental and occupational health safety - Anses Niort 60, rue de Pied de Fond, CS 28440 79024 Niort C´ edex, France ABSTRACT In poultry flocks, flock weight unifor- mity is often defined as the percent individuals within 10% of the mean body weight (BW) and the variability of this uniformity can be expressed as the CV of BW. Flock weight uniformity is a standardized and objective measured, and could potentially be used as a welfare in- dicator; however, little is known about the relationship between flock uniformity and other production mea- sures on-farm or at slaughter. The aim of this study was to investigate the associations between carcass weight uniformity (CV of BW) and production measures on- farm and at slaughter in Norwegian commercial broiler flocks. A total of 45 randomly selected mixed-sex Ross 308 broiler flocks were visited prior to slaughter at 28 to 30 D of age (average slaughter age 30.6 D). All flocks were raised under similar farm management systems. The Welfare Quality protocol for broilers was used to assess different animal welfare indicators in each flock. All production data from the slaughterhouse were col- lected for each flock, including carcass weight unifor- mity (%), mortality (%), growth rate (g), feed con- version ratio (FCR), and rejected birds (%) in differ- ent rejection categories. Univariable and multivariable linear regression models were used to investigate the associations between flock weight uniformity and pro- duction and welfare measures. The results showed that flock uniformity varied from 11% to 18% between flocks within the same hybrid, similar management standards, and similar slaughter age (day 29 to 32). Poorer unifor- mity (i.e., high CV) was associated with increased first week mortality (P < 0.004, r = 1.48, increased total mortality (P < 0.013, r = 0.01), increased FCR (i.e., less efficient growth) (P < 0.024, r = 0.06), reduced growth rate (P < 0.0012, r = −0.01), and a reduced rejection rate at slaughter (P < 0.006, r = −0.01). The results show that flock uniformity varies across broiler flocks, and is associated with several production measures. Key words: chicken, indicator, poultry, welfare, health 2019 Poultry Science 98:4261–4268 http://dx.doi.org/10.3382/ps/pez252 INTRODUCTION Animal welfare in commercial poultry flocks can be monitored using registrations routinely recorded C  The Author 2019. Published by Oxford University Press on be- half of Poultry Science Association. This is an Open Access article distributed under the terms of the Creative Commons Attribution Li- cense (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, pro- vided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com. Received December 18, 2018. Accepted April 23, 2019. 1 Corresponding author: guro.vasdal@animalia.no at the slaughterhouse (EFSA, 2012). In broiler pro- duction, footpad dermatitis (FPD) is now included as a welfare indicator in the European Broiler Direc- tive (2007/43/EC), and should be regularly collected for each slaughtered flock (Ekstrand et al., 1998a; Butterworth et al., 2015). However, animal welfare is considered a multidimensional concept consisting of 3 equally important dimensions: biological function, natural living, and subjective experience (Fraser et al., 1997; Botreau et al., 2007); and although FPD can be considered a useful indicator, it does not provide a com- prehensive or complete view of flock welfare (Allain et al., 2009; de Jong et al., 2014). To gain a more 4261 Downloaded from https://academic.oup.com/ps/article-abstract/98/10/4261/5499123 by 10125250 user on 17 October 2019