Periódicos Brasileiros em Medicina Veterinária e Zootecnia

Quality of Eggs from Layers Reared under Alternative and Conventional System

Popova, TPetkov, EAyasan, TIgnatova, M

The study aimed to compare and assess some of the quality characteristics (morphology, colour of the yolk, total carotenoid content and fatty acid profile) of eggs obtained from hens reared conventionally or in alternative system having access to pasture. Twenty eggs of each rearing system were analysed for the above characteristics. The eggs obtained from the layer reared under the alternative system were significantly heavier than the conventional ones, displayed higher diameters of the albumen and albumen index, as well as increased diameter and weight of the yolk. On the other hand, their shell thickness and Haugh units were lower when compared to the eggs from conventionally reared hens. The colour of the eggs from the alternative system was darker and they had lower values of L* and higher of a* in the yolk, corresponding to the significantly higher content of the total carotenoids in comparison to the eggs obtained from the hens reared conventionally. Furthermore, the eggs from the hens having access to pasture showed clear advantage in the fatty acid profile and the related lipid nutritional indices. In general, the rearing in alternative system reduced considerably the content of C14:0, C16:0, C18:0, C16:1n-7 and C18:1n-9, as well as the saturated (SFA) and monounsaturated fatty acids (MUFA). On the other hand, with the exception of C20:3n-6, the contents of both individual and total polyunsaturated fatty acids (PUFA) were dramatically increased in the eggs from the hens reared in the alternative system. This led to favourably decreased values of n-6/n-3 ratio as well as values of both atherogenic (AI) and thrombogenic (TI) indices but augmented ratio between hypo- and hypercholesterolemic fatty acids.(AU)

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