Can eggshells indicate stressor exposure in free-range laying hens?

Area of Science:

• Animal Science
• Animal Welfare
• Poultry Science

Background:

• Monitoring laying hen welfare in large UK flocks (up to 16,000 birds) presents significant challenges.
• Eggs, as a daily output, show potential for welfare monitoring due to established links between stress and egg characteristics.

Purpose of the Study:

• To explore the associations between environmental stressors and egg characteristics in laying hens.
• To investigate eggshell texture defects as a potential proxy for hen welfare.

Main Methods:

• Study 1: Induced social and heat stressors in hens, scoring daily eggshell defects (texture, shell characteristics).
• Study 2: Assessed eggshell texture in commercial flocks before and after avian influenza-enforced indoor housing, correlating with automated grading data (shell strength, color).

Main Results:

• Stress treatments in Study 1 increased eggshell texture defects.
• Enforced indoor housing in Study 2 led to more texture defects, weaker shell strength, and darker egg color.
• Manually scored eggshell texture correlated significantly with automated shell strength and color data.

Conclusions:

• Eggshell texture defects show promise as a welfare indicator for laying hens under stress.
• Existing industry data (shell strength, color) may be valuable for assessing hen welfare.
• Further validation is needed to generalize findings across different stressors and environments.