Strain differences and effects of different stocking densities during rearing on the musculoskeletal development of pullets

Abstract

There are few published studies on the effect of stocking density ( SD ) of pullets, particularly between different genetic lines. The objectives of this study were to determine if strain or SD affects musculoskeletal development of pullets and determine any impact on the productivity and keel bone health of adult hens. Lohmann Selected Leghorn Lite ( LSL ), Dekalb White ( DW ), and Lohmann Brown ( LB ) pullets were reared at 4 different SD (247 cm 2 /bird, 270 cm 2 /bird, 299 cm 2 /bird, and 335 cm 2 /bird) in large cages furnished with elevated perches and a platform. At 16 wk of age, the keel bone, the muscles of the breast, wings, and legs, and the long bones of the wings and legs were collected to compare keel bone development, muscle growth, and bone breaking strength ( BBS ) between strain (adjusted for bodyweight) and SD treatments. Stocking density did not have an effect on the metasternum length, height, or area of the keel bone, the weights of the bicep brachii, pectoralis major or pectoralis minor, or the BBS of any of the selected bones. However, strain differences were found for all keel bone characteristics, all muscle weights, and the majority of BBS measures. The keel metasternum, height, and overall area of the keel bone were found to be smaller in LB pullets compared with LSL and DW pullets ( P < 0.0001); however, cartilage length and overall percentage of the cartilage present on the keel bone was greatest in LB pullets ( P < 0.0001). Leg muscles were heaviest in LB pullets ( P < 0.05); however, breast muscles were heavier in LSL and DW pullets ( P < 0.0001). Lohmann Brown pullets had lower BBS of the tibia ( P < 0.0001) and femur ( P < 0.0001) compared with LSL and DW pullets, whereas DW pullets had greater BBS of the humerus ( P = 0.033). Additionally, there was a higher prevalence of keel bone fractures at 50 wk of age in LB hens compared with DW ( P = 0.0144). Overall, SD during rearing used in this study had little impact on the musculoskeletal growth of pullets; however, significant differences were found between strains which may reflect strain-specific behavior. Additionally, differences in keel bone development between strains may lead to differences in keel bone damage in adult hens.

Does wing use and disuse cause behavioural and musculoskeletal changes in domestic fowl ( Gallus gallus domesticus )?

“…White-feathered laying hens have a lighter body mass and smaller leg muscles (as also observed in this study) [40,41] and have a smaller wing-loading (mass of bird over wing area) burden compared with brown-feathered birds [45]. Brown-feathered hens also have been shown to have smaller flight muscles and less keel area compared with white-feathered hens [40]. Furthermore, brown-feathered chicks spent more time on the ground [42], and used aerial spaces and perches less than white-feathered chicks [43].…”

“…Hypothetically, the asymmetric use of the wings could unequally distribute force and velocities onto the keel leading to a deviation or fracture in the direction of muscle action. Additionally, strain-specific differences are known to occur, with typically brown-feathered laying hens being heavier and less aerial compared with white-feathered laying hens [ 40 – 45 ], which needs to be considered.…”

“…Open Sci. 10: 220809 hens being heavier and less aerial compared with white-feathered laying hens [40][41][42][43][44][45], which needs to be considered.…”

In pursuit of a better broiler: welfare and productivity of slower-growing broiler breeders during lay

“…A random subsample of 10 hens per pen was individually palpated for keel bone fractures and deviations at 52 wk of age. Keel bone deviations were defined as abnormal curvature of the keel bone, either ventral or longitudinal, and keel bone fractures were identified as the presence of bony callus on the ventral or lateral surfaces of keel bone ( Casey-Trott, 2016 ; Fawcett et al., 2020 ). Hens were scored separately by 2 researchers (T.M.W.…”

Lighting, density, and dietary strategies to improve poultry behavior, health, and production

“…Working on laying chickens, SD influenced musculoskeletal traits, especially the amount of cartilage on keel bone and leg muscle weight in leghorn pullets. Birds reared at low SD (247 cm 2 /bird) had the heaviest leg muscles and the lowest cartilage amount on keel bone (Fawcett et al 2020).…”