Vitamins A, E and fatty acid composition of the eggs of caged hens and pastured hens

Summary

This peer-reviewed study, published in Renewable Agriculture and Food Systems, compared the nutritional composition of eggs from conventionally caged hens with those from hens raised on pasture. The research likely demonstrates that pasture access — and the associated consumption of fresh forage, insects and diverse plant material — is associated with meaningfully higher levels of fat-soluble vitamins and more favourable fatty acid profiles in eggs. The findings contribute to the evidence base linking production system and animal diet to the nutrient density of animal-derived foods.

UK applicability

Although conducted in the United States, the findings are broadly applicable to UK pasture-based poultry systems, given comparable nutritional mechanisms; they are relevant to UK policy discussions around free-range and organic egg labelling standards and consumer guidance on egg quality.

Key measures

Vitamin A concentration (IU or µg/egg); vitamin E concentration (mg/egg); fatty acid composition including omega-3, omega-6 and saturated fatty acids (%); omega-6:omega-3 ratio

Outcomes reported

The study measured and compared concentrations of vitamins A and E and fatty acid profiles (including omega-3 and omega-6 fatty acids) in eggs from hens kept in conventional cages versus those raised on pasture. It likely found that pasture-raised hens produced eggs with higher nutrient concentrations, reflecting access to diverse forage.

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