Effects of photoperiod and protein content in feed on keel bone status and productivity in layer hens
Year: 2026
Type: conference-paper
Abstract: Keel bone fracture (KBF) is a major welfare problem in commercial layer hens with high prevalences (36-97%). KBF can reduce welfare due to pain and can cause economic losses due to lower feed efficiency and poor egg quality. Several factors may influence KBF occurrence, such as late ossification of keel bone, early onset of lay and high egg productivity. The aim of the study was to investigate if different managements can reduce the risk of developing KBF. The KBF development and productivity were compared between layer hens with different treatments which can delay the onset of lay (short day and lower protein). The hypothesis was that delaying onset of lay could strengthen bone development thus reducing the prevalence of KBF. This study has a 2×2 factorial design, with 2 main factors, photoperiod (short-day: 8h, normal-day: 14h) and protein content in feed from onset until post-peak of lay (low protein feed: 16%, regular feed: 17%, commercial feeds). In total 320 Lohman LSL lite hens were split into 4 groups and kept in enriched cages of 10 birds each. The number of eggs and egg weight were recorded at cage level daily. All hens were weighed and their keel bone was X-rayed biweekly. To evaluate egg traits (e.g. size, shell weight and thickness), eggs from 2 cages per group were collected biweekly. Egg shell strength was measured every 3 months on 30 eggs/group. The data was collected from first egg to end of production. The continuous data was analyzed by ANOVA and the status of KBF was analyzed by logistic regression. The egg weight was lowest in short-day/low protein group from onset to peak of lay (p<0.05). Body weight and laying rate were lower from onset to peak of lay in short-day/low protein group than normal-day/low protein group, as well as short-day/regular feed group (p<0.05). Shell strength was lower during peak of lay and shell weight was lower from onset to post peak in short-day group than normal-day group within the hens fed low protein feed (p<0.05). There was no significant difference in the age of the onset of lay. The prevalence of KBF was higher in short-day than normal-day groups in 39 and 41 weeks old (wo) (p<0.05), and tends to increase more rapidly in normal-day groups than short-day groups. The short-day groups showed more severe callus formation than normal-day groups in 39 and 41 wo (p<0.05). Despite no significant delay in onset of lay, these results indicate that lower protein content in feed during peak of production does not affect productivity but have negative effects on KBF occurrence. Short photoperiod might be effective to slow the increase of KBF prevalence, but combination of short day and low protein feed negatively affected the productivity.
Language: English
Subfield: Small Animals
Field: Veterinary
Domain: Health Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7167996791
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