Effects of agricultural systems on egg nutritional quality

Abstract

Eggs are a rich source of nutrients beneficial to human health. Market analysis shows increasing European egg production and consumption. Organic egg production differs from conventional systems (free-range and indoor) in the exclusive use of organically grown feed. Organic and conventional free-range systems share the free access to open-air runs but organic flocks have greater management restrictions, which could potentially differentiate egg composition. In order to investigate the effect of management on egg nutritional quality, three major egg production systems were explored; caged, conventional free-range and organic. The hypothesis developed is based on benefits of increasing pasture and free-range behaviour. To fully investigate the effect, these systems were considered within a framework of a meta-analysis (Chapter Two), a farm survey (Chapter Three) and a retail survey (Chapter Four). In all chapters it was found that management does affect the overall egg nutritional quality, with organic having higher omega-3 (n-3) fatty acids than free-range systems (P<0.05 (Chapter Two), P<0.01 (Chapter Three) and P<0.001 (Chapter Four)) and higher carotenoids than all conventional systems (P<0.001 in Chapter Four). At the same time Chapter Four detected seasonal effect for vitamin D3 (P<0.001) and B2 (P<0.01) and interactions with management (B9, D3). In Chapter Five, the effect of a sustainable and alternative protein source on egg fatty acid profile was investigated to account for the impact of replacing soybean with insect meal on egg fatty acid within an experimental trial framework. The partial replacement of soybean with insect meal had both positive and negative effects on egg fatty acid composition, flagging promising the replacement of soybean in terms of overall egg nutritional quality. Implications of choosing organic over conventional eggs to human health are focused on higher intakes of long chain n-3 fatty acids, carotenoids and potentially of vitamin A and E. Standardizing egg concentration in vitamin D3, B2 and B9 between summer and winter is also suggested.