Integument, mortality, and skeletal strength in extended production cycles for laying hens – effects of genotype and dietary zinc source

Abstract

1. This study on long-life layers, covering the period 20-100 weeks of age, investigated longitudinal effects on mortality, layer integument, and skeletal properties in Bovans White (BoW) and Lohmann Selected Leghorn Classic (LSL), with or without supplementation with dietary organic zinc (Zn).2. Two experiments, using 1440 layers in furnished small group cages (FC) and 1834 layers in a traditional floor housing system (Floor), were run in parallel. Each replicate consisted of five adjacent cages containing eight hens in FC, or a pen with 102 layers in the Floor group.3. Mortality was recorded daily. Integument and keel bone condition were scored at 35, 55, 85, and 100 weeks of age on 20% of the layers. Tibial strength was recorded from 933 layers at 100 weeks. Statistical analyses were performed on replicate means, with four to five and nine replicates per combination of hybrid and diet in Floor and FC groups, respectively. 4. Cumulative mortality was 9.6% and 16.3% in FC and Floor, respectively, and increased in the latter part of the production cycle, particularly in the Floor group. 5. In FC, LSL had inferior feather cover, less keel bone deviation, and shorter claws than BoW. In Floor, LSL had superior feather cover, less severe vent wounds, more bumble foot, and cleaner plumage than BoW. In both production systems, claws grew longer and keel bone deviation became more severe with age. 6. In FC, layers fed organic Zn had lower body weight and less keel bone deviation at 100 weeks of age. 7. In conclusion, keel bone integrity, claw length, and mortality rate are potential threats to welfare in long-life layers. Feather pecking is a problem that needs addressing at an early stage in the production period. On the whole, organic Zn did not improve welfare conditions in long-life layers.

A systematic review of potential productivity, egg quality, and animal welfare implications of extended lay cycles in commercial laying hens in Canada

“…Supplementing diets with organic, bioavailable zinc, as compared to zinc made available through inorganic mineral salts (ZnO), did not significantly affect the skeletal integrity (measured using keel bone deformation) and mortality between 15 and 100 wk of age ( Wall et al, 2022 ). Bioavailability of essential compounds was also the focus in studying the effects of MBM and OSM.…”

Spatial distribution, movement, body damage, and feather condition of laying hens in a multi-tier system

“… Nannoni et al (2022) similarly indicated that worse plumage condition was found in birds with more freedom to move vertically in combi aviaries as time progressed. In another study on long-life layers, birds kept in a traditional floor housing system had a total feather score of less than 12 at 100 wk of age ( Wall et al, 2022 ). As the age of the birds increased, the condition of the hens' plumage deteriorated ( Sokołowicz et al, 2023 ).…”

“…Previous research has reported on egg quality ( Molnár et al, 2018 ; Jabalera et al, 2022 ), diseases ( Buyse et al, 2023 ), and physical condition ( Wall et al, 2022 ; van Eck et al, 2023 ) of hens near the end of the laying cycle. Furthermore, the high-intensity physical activity of hens declined with the increasing of age ( Kozak et al, 2016 ) which may lead to the increase of the population size of lower tier in the multitier system, and other issues of bird's health and resources allocation.…”

Genetics of tibia bone properties of crossbred commercial laying hens in different housing systems

“…At 15 weeks of age, the pullets were transferred to the poultry experimental facility at the Swedish Livestock Research Centre Lövsta and subsequently housed either in furnished 8-hen cages or in a 1-tier floor housing system. The housing systems and management has been described in Wall et al . (2022) .…”

“…As the dietary treatment was not significantly associated with bone strength (average difference of 1.7 N, P = 0.54 in a linear model including housing system and crossbred), we did not include diet in any of the further analyses in this paper. A detailed description of the organic zinc supplementation treatment and analyses of its effect on mortality, integument and bone strength was published in Wall et al . (2022) .…”