The importance of rest in young domestic fowl Anne E. Malleau 1 , Ian J.H. Duncan * , Tina M. Widowski, James L. Atkinson Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada Accepted 24 June 2006 Available online 8 August 2006 Abstract This project investigated whether or not chicks of broiler and layer strains would adapt to a simulated brooding cycle which allowed them to rest synchronously, and how allowing the chicks to rest would affect growth and maintenance activities. There were four trials with four groups of 10 layer chicks and four groups of 10 broiler chicks in each trial. Half the groups were subjected to a long-day schedule (LD) of 19.33 h light (L):4.67 h dark (D); half to a simulated brooding cycle (SBC) which consisted of the same long day but with alternating 40 min light:40 min dark periods throughout the main light period. There were significant strain effects for growth rate, gain:feed, body composition and shank length (P < 0.01); however, no differences were found between lighting treatments (P > 0.10). All chicks spent a large proportion of the first 14 days resting. Chicks on the SBC rested more than chicks on the LD (P < 0.05). Chicks on the SBC had highly patterned levels of activity which did not compromise weight gain or feed efficiency. # 2006 Elsevier B.V. All rights reserved. Keywords: Chick behaviour; Feed efficiency; Lighting; Rest; Simulated brooding cycle 1. Introduction The function of sleep still remains a mystery. Sleep occurs in all mammals and birds, and in most reptiles. Physiological recuperation of the body in terms of energy conservation and tissue restoration and growth seem to be the primary functions of sleep. However, it has also been suggested that sleep might increase an animal’s chances of survival by making it immobile at times of day when it would be particularly vulnerable (Meddis, 1975). Similarly, Blokhuis (1984) www.elsevier.com/locate/applanim Applied Animal Behaviour Science 106 (2007) 52–69 * Corresponding author. Tel.: +1 519 824 4120x53652; fax: +1 519 837 9873. E-mail address: iduncan@uoguelph.ca (I.J.H. Duncan). 1 Present address: Animal Compassion Foundation (AWhole Foods Market Foundation), 550 Bowie Street, Austin, TX 78703, USA. 0168-1591/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2006.06.017