Opportunities for exercise during pullet rearing, Part I: Effect on the musculoskeletal characteristics of pullets

Abstract

Increased load-bearing exercise improves bone quality characteristics in a variety of species, including laying hens. Providing increased opportunities for exercise during the pullet rearing phase, a period of substantial musculoskeletal growth, offers a proactive approach to reducing osteoporosis by improving bone composition. The main objective of this study was to determine whether differing opportunities for exercise during rearing influences pullet musculoskeletal characteristics. Two flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either standard, conventional cages (Conv) or an aviary rearing system (Avi) from day-old chicks until 16 wk of age. The keel bone and the muscles and long bones of the wings and legs were collected at 16 wk to measure muscle growth differences between rearing treatments and quantify bone quality characteristics using quantitative computed tomography (QCT) and bone breaking strength (BBS) assessment. Keel bone characteristics and muscle weights were adjusted for BW and analyses for QCT and BBS included BW as a covariate. At 16 wk of age, rearing system had an effect on the majority of keel bone characteristics (P < 0.05). The length of the keel metasternum, caudal tip cartilage length, and the overall percentage of cartilage present on the keel at 16 wk was greater in the Avi pullets compared to the Conv pullets (P < 0.01). Wing and breast muscle weights of the Avi pullets were greater than the Conv pullets (P < 0.001), but leg muscle weights were greater in the Conv pullets (P = 0.026). Avi pullets had greater total bone density, total cross-sectional area, cortical cross-sectional area, total bone mineral content, and cortical bone mineral content than Conv pullets for the radius, humerus, and tibia (P < 0.001). Avi pullets had greater BBS compared to the Conv pullets for the radius, humerus, and tibia (P < 0.01). Increased opportunities for exercise offered by the aviary rearing system increased muscle and bone growth characteristics in pullets at 16 wk of age.

Keywords: Exercise; Keel bone; Musculoskeletal growth; Pullet; Rearing system.

Figure 1.

Images of the Farmer Automatic Portal Pullet rearing system (A and B) and conventional cage rearing system (C). Image A depicts the area inside the system (System Area: 183,272 cm²) equipped with feeders, waterers, perches, a suspended platform (32,371 cm²) in the centre of the system (Total System Area: 215,643 cm²). Image B depicts 9 platforms (Platform Area: 118,887 cm²) on the outer edge of the system, which are opened up at 6 wk of age to allow for access to the litter portion (Litter Area: 235,767 cm²; Total Aviary Area: 570,297 cm²) of the aviary enclosure seen in the bottom corner of the image. Image C depicts the conventional cage rearing system (Total Cage Area: 2,322 cm²).