Effects of age and time of day of sampling on proximate and fatty acid composition of whole eggs from two strains of laying hens

Abstract. The aim of the present study was to determine the effects of breed (Naked Neck – NN – and Lohmann Brown – LB), age (46 to 49 weeks) and the time of day of sampling (morning eggs – M – and afternoon eggs – A) on the proximate and fatty acid composition of whole eggs.

Eggs of commercial hens (LB) had significantly (P < 0.001) less fat, ash and protein and lower dry-matter content (more water content) compared to the autochthonous breed (NN). The NN eggs contained significantly (P < 0.001) more SFA (saturated fatty acid) and less PUFA (polyunsaturated fatty acid) than LB ones, while the share of the eggs' total n-3 fatty acids did not differ significantly between breeds. The share of total MUFA (monounsaturated fatty acid) significantly (P = 0.011) decreased, while the share of total PUFA, n-6 and n-6 / n-3 ratio significantly increased (P < 0.001; P < 0.001; P = 0.032, respectively) with age of hens. Additionally, compared with morning eggs, afternoon eggs had a significantly (P = 0.046) higher share of total n-6 fatty acids.

PCA (principal component analysis) offered a good separation of the samples according to breed and age when two first principal component were extracted. PC1 was positively related to parameters of proximate composition and SFA content, while PC2 was positively determined by PUFA, n-6 and n-3 content. Eggs of autochthonous hens (NN) were located in the positive area of PC1, whereas those from the commercial hens (LB) were in the negative quarter, which indicates opposite characteristics.