NCSU Study: Impact of Environment and Genetics on Cage-Free Egg Production

Brown Hens

Shift Towards Cage-Free Production

The shift towards cage-free egg production is being driven by consumer preferences, retail demands, and legislative changes in some states. Currently, about 34% of the laying-hen industry uses cage-free systems, with projections from the USDA Agricultural Marketing Service indicating this could double by 2026.

Implications for Laying-Hen Strains

This shift raises questions about the suitability of different hen strains for cage-free systems and the need for revised selection parameters to ensure animal welfare and productivity.

“Traditionally, White laying hens have been used in cages due to their high productivity, while Brown strains are preferred for cage-free systems because of their performance and behavior,” said Bhavisha Gulabrai, a graduate research assistant at North Carolina State University, at the 2024 International Poultry Scientific Forum. She emphasized the necessity of understanding how cage-free environments affect production and stress in different hen strains.

Study Overview

Gulabrai and her team hypothesized that White hens would experience higher stress levels than Brown hens in cage-free environments, but production attributes would remain unaffected. The study included 300 birds from four strains: Hyline W36 White, H&N White, Hyline Brown, and Bovans Brown.

All hens, except for the Hyline W36, were raised cage-free until 11 weeks of age. The W36 strain was reared in cages, potentially affecting their outcomes. At 11 weeks, all hens were moved to research facilities and placed in floor pens. Data on egg production, feed consumption, body weight, and egg quality were collected from 17 to 56 weeks of age. Stress was measured using plasma corticosterone levels, heterophil-lymphocyte ratios, and heat-shock protein (HSP) gene expression.

Key Findings

– **Production Metrics**: Bovans Brown hens produced the most eggs and had the highest yolk color density. They were also the heaviest and consumed the most feed but had the least efficient feed-conversion ratio. Hyline Browns were the second heaviest and produced more extra-large eggs but laid more floor eggs. H&N White hens were the third heaviest but laid fewer eggs. The W36 hens were the lightest.

– **Stress Indicators**: There were no significant differences in corticosterone levels across strains, indicating similar short-term stress levels. However, heterophil-lymphocyte ratios were higher at peak lay, suggesting increased long-term stress. HSP gene expression varied between strains and time points, indicating different stress responses throughout the laying cycle.

Conclusions

The study concluded that while production attributes varied between strains, stress responses did not show significant differences. Bovans Brown hens were the top producers but had the lowest feed-conversion efficiency. Hyline Browns offered a balance of productivity and cost-efficiency in cage-free systems.

These findings help table-egg producers make informed decisions about selecting hen strains for cage-free production, balancing productivity and animal welfare.

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