Keel bone fractures are more prevalent in White Leghorn hens than in Red Jungle fowl hens—A pilot study

Abstract

Fractures and deviations to the keel bone are common in commercial laying hens, with reported variations in occurrence across strains and breeds. The aetiology is not fully understood, however, modern genetics and selection for efficient egg production has been claimed to be important factors for the keel bone fractures. To explore this further, we investigated keel bones from two different breeds, representing different degrees of selection for egg production: Red jungle fowl (n = 82), and White Leghorn (n = 32), where the latter is a selected laying breed which is the origin for many modern laying hen hybrids. Keel bones from a total of 116 birds, 53 hens and 63 roosters, were examined by necropsy at 80 weeks of age. All birds were raised in modified aviaries in the same holding facility. Overall, 24.5% of the hens had one or more fractures to the keel, with a difference in the prevalence between hens from the two breeds (p<0.01): 10% (95% CI: 3.7–24%) in the Red Jungle fowl hens and 69% (95% CI: 37–90%) in the White Leghorn hens. No roosters, regardless of breed, had keel bone fractures. Mild to moderate keel bone deviations were present in 54% (95% CI: 25–80%) of the hens and 4.7% (95% CI: 0.5–30%) of the roosters, all White Leghorns.

Skeletal variation in bird domestication: limb proportions and sternum in chicken, with comparisons to mallard ducks and Muscovy ducks

“…The crookedness of the keel has been shown to be hereditary and influenced by early roosting conditions ( Blount, 1933 ; Warren, 1937 ; Waters, 1949 ). Our observations reveal that this is not a feature unique to domestic varieties, as has been previously reported ( Kittelsen et al, 2021 ).…”

“…The sternum varies in shape and proportions and is a source of intensive study in poultry research concerned with welfare due to widespread reports of damage ranging between 30 and 100% of commercial hens ( Buckner et al, 1949 ; Fleming et al, 2004 ; Harlander-Matauschek et al , 2015 ; Toscano et al, 2020 ). Keel damage may include crookedness or bending, as well as fractures ( Casey-Trott et al, 2015 ) and has been observed to occur in different proportions between breeds—potentially also related to wing loading—and between sexes ( Kittelsen et al, 2021 ; Stratmann et al, 2016 ). Deformations of the keel can be divided into two types: fractures, defined as sharp bends, fragmented sections or shearing of the keel with or without thickened bone (callus) ( Fleming et al, 2004 ; Eusemann et al, 2018 ; Tracy et al, 2019 ; Thøfner et al, 2020 ); and deviations, defined as abnormally shaped bone containing section(s) that vary from an ideally perfect two-dimensional straight plane that has not resulted from fracture ( Casey-Trott et al, 2015 ).…”

“…Keel crookedness has been reported to have environmental and genetic origins, appearing mostly when chickens are given the opportunity to perch ( Blount, 1933 ; Warren, 1937 ; Waters, 1949 ; Buckner et al, 1949 ; EFSA, 2015 ; Gebhardt-Henrich, Toscano & Würbel, 2017 ). However, whether crookedness of the keel and other alterations of sternum characteristics typically found in domestic chicken are associated with domestication in its initial, less intense phase ( Vigne, 2011 ), or if it appeared only with breed formation and improvement has not been determined ( Blount, 1933 ; Warren, 1937 ; Waters, 1949 ; Hyre, 1995 ; Fleming et al, 2004 ; Kittelsen et al, 2021 ). We would expect that wild forms exhibit less deformed and more compact keel bones, i.e.…”

Abnormal Bone Metabolism May Be a Primary Causative Factor of Keel Bone Fractures in Laying Hens

“…Additionally, although the current study suggested that keel bone damage could be associated with abnormal bone metabolism reflected by changed serum markers in relation to bone turnover in laying hens, this study had limitations, such as the younger hens, a shorter experimental period, a smaller sample size, and the lack of the analysis of bone mineralization markers and serum RANKL level, as well as the age at onset of lay and the egg production of laying hens in each group. Previous studies reported that these factors could affect the development of KBFs in laying hens [ 26 , 45 ]. Besides, one of the most important limitations is the young age of the laying hens.…”

Productive performance, perching behavior, keel bone and other health aspects in dual-purpose compared to conventional laying hens

“…In previous studies, fracture risk was at least 80% lower in hens in which egg production was suppressed compared to egg-laying control hens ( Eusemann et al, 2018b ; Eusemann et al 2020 ). In addition, fracture prevalence has recently been found to be significantly lower in the unselected red jungle fowl, that is, the wild ancestor of the domestic chicken, compared to White Leghorn hens, a typical layer strain ( Kittelsen et al, 2021 ). Furthermore, some high performing layer lines (320 eggs/yr) showed a higher prevalence of keel bone fractures and more severe deviations compared to their moderately performing counterparts (200 eggs/yr) ( Eusemann et al, 2018a ; Eusemann et al, 2020 ).…”