Mortality risk on farm and during transport: a comparison of 2 broiler hybrids with different growth rates

ABSTRACT: Mortality in broilers is often associated with poor health and welfare and has a complex and multifactorial etiology. Recent studies under experimental conditions indicated that genetic selection for fast growth is an important risk factor for mortality in broiler chickens. However, the knowledge on broiler mortality in general, and in slower growing broilers in particular, under commercial conditions is still limited. This retrospective cohort study aimed to describe mortality risk on farm and during transport in 2 broiler hybrids with different growth rates, Ross 308, and Hubbard JA787, and to estimate the association between hybrid and mortality at different stages of the production cycle. The study sample consisted of 64,651,804 broilers from 4,228 flocks and 139 farms slaughtered from January 1st, 2015, to June 22nd, 2021. Analysis of on-farm mortality was restricted to broiler flocks slaughtered in the period July 2017 to July 2018 due to changes known to affect FWM. The effect of hybrid on mortality during 3 different production stages (first week mortality (FWM), mortality after the first week (MAFW), and mortality during transport (DOA)), was assessed using mixed effect negative binomial regression models. Descriptively, there were notable differences in mortality at all stages of the production cycle, with higher mean mortalities in Ross 308 (1.40% FWM, 3.05% MAFW, and 0.063% DOA) than in Hubbard JA787 (0.76% FWM, 1.49% MAFW, and 0.015% DOA). In the analysis, the largest estimated difference was found for dead on arrival under cold conditions, where mortality was almost 5 times higher in Ross 308 compared to Hubbard JA 787 (IRR: 4.70, 95% CI: 3.74–5.90). The estimated difference in FWM between hybrids was highest during autumn, with an estimated risk approximately 1.6 times higher in Ross than in Hubbard (IRR: 1.56, 95% CI: 1.30–1.86). For MAFW, the estimated risk was approximately 2 times higher in Ross than in Hubbard (IRR: 2.13 95% CI: 1.82–2.49). The findings in this study emphasize the need for more knowledge on causes of mortality in broilers including effects of genetic factors as basis for preventive measures

Comparison of flock characteristics, journey duration and pathology between flocks with a normal and a high percentage of broilers 'dead-on-arrival' at abattoirs

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A Descriptive Study of Keel Bone Fractures in Hens and Roosters from Four Non-Commercial Laying Breeds Housed in Furnished Cages

The keel bone in birds is an extension of the sternum. Fractures to the keel are common in modern laying hen breeds. Several of the proposed causal mechanisms behind keel bone fractures (KBF) are linked to selection for efficient production. It is, therefore, of interest to explore whether less selected breeds have a lower occurrence of keel bone fractures compared to reports from highly selected, modern laying hen breeds. Thus, the aim of the current study was to investigate keel bones of hens from four non-commercial layer breeds. Birds were housed in furnished cages and keel bones examined at 30 and 63 weeks of age using a portable X-ray equipment. The results from this descriptive study indicate a low prevalence of keel bone fractures in hens at both ages in all four breeds. No fractures were observed in the examined roosters. The overall low numbers of fractures indicate that genetic factors may be involved and, thus that selective breeding may help to reduce the susceptibility to keel bone fractures. Finally, this study highlights the importance of poultry conservation to secure existing genetic diversity, which may be an important resource in future selection schemes.publishedVersio

Flock Factors Correlated with Elevated Mortality in Non-Beak Trimmed Aviary-Housed Layers

The use of non-cage housing systems for layers is increasing in Europe and elsewhere. Knowledge of factors that may affect mortality in these systems is important to be able to improve animal welfare, reduce mortality and enhance sustainability. The aim of this study was to investigate factors that may contribute to increased mortality in non-beak trimmed aviary-housed laying hens in Norway. A total of 39 non-beak trimmed commercial flocks (Lohmann LSL (n = 25) and Dekalb White (n = 14)) were visited between week 70 to 76 of life, and factors related to health, behaviour and management were recorded. Mean mortality in the flocks was 3% (range: 0.5–9%) and increased flock mortality was correlated with total feather loss (p p p p = 0.055). Furthermore, a low positive correlation between mortality and dust level inside the barn was found (p 3.0%) and increased feather loss which may indicate feather pecking. The results underline the importance of regularly assessment of plumage condition in commercial layer farms, as a tool to detect early signs of feather pecking in commercial aviary-housed layer flocks. This may help to target feather pecking before cannibalism breaks out

Prevalence of Keel Bone Damage in Red Jungle Fowls (Gallus gallus)—A Pilot Study

The keel bone of laying hens is prone to deviations and fractures. Recent studies in the last decade report high prevalence of this welfare concern. The causative factors are not clear; however, selection for efficient egg production has been suggested as a major contributing factor. An important step to shed light on the role of selective breeding as an underlying cause of keel bone damage (KBD) in modern laying hens is to evaluate the keel bones of the ancestor, the red jungle fowl. The aim of this study was therefore to describe the prevalence of KBD in a study group of 29 red jungle hens and roosters by autopsy. No fractures were detected in the roosters, one had a very slight deviation. One of the hens had a fracture to the keel and 10 hens had a very slight deviation. Large scale studies are needed to disentangle the effect of different factors on keel bone damage

Prevalence of Keel Bone Damage in Red Jungle Fowls (Gallus gallus)—A Pilot Study

The keel bone of laying hens is prone to deviations and fractures. Recent studies in the last decade report high prevalence of this welfare concern. The causative factors are not clear; however, selection for efficient egg production has been suggested as a major contributing factor. An important step to shed light on the role of selective breeding as an underlying cause of keel bone damage (KBD) in modern laying hens is to evaluate the keel bones of the ancestor, the red jungle fowl. The aim of this study was therefore to describe the prevalence of KBD in a study group of 29 red jungle hens and roosters by autopsy. No fractures were detected in the roosters, one had a very slight deviation. One of the hens had a fracture to the keel and 10 hens had a very slight deviation. Large scale studies are needed to disentangle the effect of different factors on keel bone damage

Associations among gait score, production data, abattoir registrations, and postmortem tibia measurements in broiler chickens

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A Descriptive Study of Keel Bone Fractures in Hens and Roosters from Four Non-Commercial Laying Breeds Housed in Furnished Cages

The keel bone in birds is an extension of the sternum. Fractures to the keel are common in modern laying hen breeds. Several of the proposed causal mechanisms behind keel bone fractures (KBF) are linked to selection for efficient production. It is, therefore, of interest to explore whether less selected breeds have a lower occurrence of keel bone fractures compared to reports from highly selected, modern laying hen breeds. Thus, the aim of the current study was to investigate keel bones of hens from four non-commercial layer breeds. Birds were housed in furnished cages and keel bones examined at 30 and 63 weeks of age using a portable X-ray equipment. The results from this descriptive study indicate a low prevalence of keel bone fractures in hens at both ages in all four breeds. No fractures were observed in the examined roosters. The overall low numbers of fractures indicate that genetic factors may be involved and, thus that selective breeding may help to reduce the susceptibility to keel bone fractures. Finally, this study highlights the importance of poultry conservation to secure existing genetic diversity, which may be an important resource in future selection schemes

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

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&amp;lt;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.Funding Agencies|research council FORMASSwedish Research Council Formas [2019-02084]</p