title: Rearing system affects prevalence of keel-bone damage in laying hens: a longitudinal study of four consecutive flocks.
abstract: High flock-level prevalence of keel-bone fractures and deviations in laying hens are commonly reported across various housing systems; however, few longitudinal studies exist, especially for furnished and conventional cage systems. Load-bearing exercise improves bone strength and mineral composition in laying hens and has the potential to reduce keel-bone damage, especially if exercise is allowed during critical periods of bone growth throughout the pullet rearing phase. The objective of this study was to determine the prevalence of keel-bone damage in laying hens housed in furnished and conventional cages, and assess whether opportunities for exercise during the pullet rearing phase influenced the prevalence of keel-bone damage throughout the laying period. Four flock replicates of 588 Lohmann Selected Leghorn-Lite pullets/flock were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30-bird furnished cages (FC-S) or 60-bird furnished cages (FC-L) for adult housing. Keel-bone status was determined by palpation at 30, 50, and 70 wk of age. Age (P < 0.001) and rearing system (P < 0.001) had an effect on the presence of keel-bone fractures. The presence of fractures increased with age, and hens raised in the Avi system had a lower percentage of fractures (41.6% ± 2.8 SE) compared to hens reared in the Conv system (60.3% ± 2.9 SE). Adult housing system did not have an effect on the percentage of keel fractures (P = 0.223). Age had an effect on the presence of deviations (P < 0.001), with deviations increasing with age. Rearing system (P = 0.218) and adult housing system (P = 0.539) did not affect the presence of deviations. Keel fractures and deviations were strongly associated with each other at all ages: 30 wk: (P < 0.001); 50 wk: (P < 0.001); and 70 wk: (P < 0.001). Increased opportunities for exercise provided by an aviary rearing system reduced the prevalence of keel-bone fractures through the end-of-lay.
authors.affiliation: Campbell Centre for the Study of Animal Welfare, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1.
authors.forename: T M
authors.initials: TM
authors.lastname: Casey-Trott
authors.affiliation: Campbell Centre for the Study of Animal Welfare, Department of Population Medicine, University of Guelph, Guelph, Ontario, N1G 2W1.
authors.forename: M T
authors.initials: MT
authors.lastname: Guerin
authors.affiliation: Monogastric Science Research Centre, SRUC Auchincruive, Ayr, KA6 5HW Animal Well-Being and Behavior.
authors.forename: V
authors.initials: V
authors.lastname: Sandilands
authors.affiliation: Campbell Centre for the Study of Animal Welfare, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1.
authors.forename: S
authors.initials: S
authors.lastname: Torrey
authors.affiliation: Campbell Centre for the Study of Animal Welfare, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1.
authors.forename: T M
authors.initials: TM
authors.lastname: Widowski
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002645:Chickens; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology / Q000473:pathology / Q000662:veterinary*; D006799:Housing, Animal; D008137:Longitudinal Studies; D009864:Ontario / Q000453:epidemiology; D011201:Poultry Diseases / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D015995:Prevalence; D013249:Sternum / Q000473:pathology*
keywords: Exercise; Keel Bone; Laying Hen; Pullet; Rearing System