Age-related changes in the shell gland and duodenum in relation to shell quality and bone strength in commercial laying hen hybrids

Anna Wistedt,Lena Holm,Helena Wall,Yvonne Ridderstråle

doi:10.1186/s13028-019-0449-1

Anna Wistedt, Lena Holm + Show 2 more

Open Access

https://doi.org/10.1186/s13028-019-0449-1

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Abstract

BackgroundDuring the production period of laying hens, the number of cracked eggshells increases and the skeleton becomes brittle. Both these problems are related to ageing of the hen and cause economic problems for egg producers and impaired animal welfare. This study investigated key factors in the shell gland and duodenum related to eggshell quality and bone strength in laying hens during the production period. Five Lohmann Selected Leghorn (LSL) and five Lohmann Brown (LB), common hybrids in commercial egg production, were euthanized at 21, 29, 49 and 70 weeks (wk) of age. Blood samples for analysis of total calcium were taken at euthanization. Right femur and humerus were used for bone strength measurements and tissue samples from shell gland and duodenum were processed for morphology, immunohistochemical localisation of oestrogen receptors (ERα, ERβ), plasma membrane calcium ATPase (PMCA) and histochemical localisation of carbonic anhydrases (CA). Eggs were collected for shell quality measurements.ResultsAt age 49 week, shell and bone strength had both deteriorated, but the hens were then able to maintain the level until 70 week of age and femur bone strength even improved. The main physiological findings associated with the effects seen at 49 week were reduced gland density and a shift in balance between ERα and ERβ in the shell gland, which coincided with a reduction in CA activity in the duodenum. Somewhat surprisingly, capillary density and capillaries with CA activity both increased in the shell gland over time, the latter possibly mediated via ERβ. These findings were independent of hybrid. PMCA was found in both shell gland and duodenum, but appeared unrelated to the age-related changes in shell and bone quality.ConclusionsIn hens around half-way through the production period, both shell quality and bone strength had deteriorated. Decreased gland density and a shift in the balance between ERα and ERβ in the shell gland, co-occurring with a dramatic drop in duodenal CA activity, are suggested as possible factors involved in age-related changes in shell and bone quality.

Highlights

During the production period of laying hens, the number of cracked eggshells increases and the skeleton becomes brittle
At 49 week of age, we detected a dramatic reduction in duodenal carbonic anhydrases (CA) activity, coinciding with decreased gland density in the shell gland and a shift in the balance between oestrogen receptor alpha (ERα) and oestrogen receptor beta (ERβ) in the shell gland
We found that the total level of calcium in plasma increased with age, suggesting that the bird’s ability to use calcium for eggshell and skeleton is affected by age in other ways

Summary

Introduction

During the production period of laying hens, the number of cracked eggshells increases and the skeleton becomes brittle. Both these problems are related to ageing of the hen and cause economic problems for egg producers and impaired animal welfare. This study investigated key factors in the shell gland and duodenum related to eggshell quality and bone strength in laying hens during the production period. They produce eggs with decreased shell quality, resulting in substantial economic losses due to cracked shells. Due to net efflux of calcium from the medullary bone of the skeleton, the hen becomes osteoporotic, which affects bone strength and causes animal welfare problems in the table egg industry [4,5,6]

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