Consideration of dietary protein level for laying hen production and egg quality during storage

Although crude protein (CP) is an important component of laying hen diets, there is still conflicting evidence on the impact of dietary CP on egg production, egg output and quality of stored eggs. This study aimed to evaluate the effects of various dietary CP levels, i.e. 172, 158, 148 and 113 g/kg, respectively, in isocaloric (11.50 MJ/kg metabolizable energy) diets on the internal egg quality of stored eggs obtained from the end of production laying hens. The impact of diets on egg production was also reported. Accordingly, one-hundred-sixty-eight Hy-line Brown laying hens were randomly allocated to four dietary treatments with seven replicates per treatment, from 75 to 83 w age. Three eggs per cage were collected during the last day of the experiment and stored for 8 weeks at 15 C-degrees as egg quality measurements were taken every 4 weeks (0, 4 and 8 weeks after storage). Overall, feeding lower dietary CP reduced layers feed intake (P < 0.05), hen weight (P < 0.001) and egg production (P < 0.05). Lower dietary CP reduced egg weight (P < 0.001) but did not have an impact on the rest of the studied variables during storage. Birds fed diets containing field beans, sunflower or rapeseed meals produced eggs with denser coloured yolks (P < 0.001). Any observed changes in egg quality confirmed the expected effects of egg storage.