Review: The effect of grass and herbs in organic egg production on egg fatty acid composition, egg yolk colour and sensory properties

摘要

In organic egg production it is required that the hens have access to pasture or forage material, which offers a wide range of various plant material. In the temperate climate, grasses, herbs and legumes are cultivated in the pasture for the hens, or the forage material may be fed as silage or dried. The effects of grasses and herbs consumed by the egg laying hen on the egg quality parameters of fatty acid composition, yolk colour and carotenoid content, and the sensory properties are elucidated. Forage material of grasses and herbs typically affects the egg yolk fatty acid composition towards a relative higher content of polyunsaturated fatty acids and in particular n-3 fatty acids, which decreases the ratio of n-6-3 from 11 to 19 in eggs from hens without access to pasture or forage material to similar to 5 in eggs from hens on grass pasture. The egg yolk colour is highly affected by plant material type and intake of the hen, where different carotenoids of different herbs are reflected in the yolk carotenoids. Pastures of grass, alfalfa silage and stinging nettle are plant sources with high potential of affecting the egg yolk to a more reddish and yellow colour. Sensory properties of eggs from hens fed forage material or on pasture appear to be affected in some experiments, however, not as a general result. The amount of intake of the forage materials is essential for its impact on the egg quality, and the presently reported intakes span from 6 g/hen/day to 126 g/hen/day, which depend on both the forage material as well as the hen.