Aggression and social rank fluctuations in precision-fed and skip-a-day-fed broiler breeder pullets

T. E. Girard, M. J. Zuidhof, C. J. Bench, Aggression and social rank fluctuations in precision-fed and skip-a-day-fed broiler breeder pullets, Applied Animal Behaviour Science, Volume 187, 2017, Pages 38-44, ISSN 0168-1591,

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In broiler breeders, conventional skip-a-day feeding leads to hunger-related aggression. As an alternative, a precision feeding system was developed to provide small meals to individual birds multiple times each day, sheltered from competition. Two objectives investigated whether: 1) aggression among pullets; and 2) the number of social rank fluctuations differed between precision and skip-a-day feeding systems. Using a randomized complete block design, a precision-fed and skip-a-day-fed pen of broiler breeders was represented in each of 6 blocks (Total = 540 pullets; 45 Ross 308 pullets per pen; 12 pens with N = 6 pens per treatment). Pen was the experimental unit. Aggressive encounters (eg. aggressive pecking, fighting, and threat behaviours) were recorded via continuous observations weekly from 10 to 21 weeks of age. Birds not involved in aggressive encounters or threats were categorized as ‘non-participants’. Using an Aggression Rank Index, the rank of each pullet was determined by the number of aggressive encounters and threats won divided by the total number of aggressive encounters and threats. Rank fluctuations were used to measure the impact of feeding system on overall group stability within a pen. Treatment differences were analyzed using a generalized linear mixed model. Precision-fed pullets were more aggressive compared with skip-a-day-fed pullets (12.73 ± 0.61 vs. 8.02 ± 0.48, respectively; F1,10 = 36.35; P = 0.0001). However, no difference was found in the number of rank fluctuations. Overall, the increased aggression exhibited in precision-fed pullets did not appear to cause social rank stability concerns.