Effect of Production System and Flock Age on Egg Quality and Bacterial Load14 April 2014
New research from Australia reveals that overall eggshell quality was better and there was less bacterial contamination on eggs from caged hens than those kept on free-range.
The shell of the egg is essential in providing shape to the egg and ensuring safe packaging of the internal contents; however, shell defects have been shown to increase the risk of microbial contamination of eggs.
Reporting a study aimed to investigate the effect of production system and flock age on egg quality and total bacterial load in commercial laying hens in Journal of Applied Poultry Research, Samiullah of the University of New England and co-authors there and at the University of Adelaide describe collecting eggs from commercial cage and free-range flocks at the ages of 25, 35, 45, 55, 65 and 75 weeks.
From each collection per flock, 30 eggs were processed for the eggshell and egg internal quality determination, 30 eggs for cuticle estimation, 30 eggs for mammillary layer ultrastructural features scoring and 60 eggs for egg microbial enumeration.
Translucency score and shell reflectivity were significantly higher in free-range eggs and increased with flock age in both production systems.
Egg weight, shell weight, percentage shell, shell thickness, albumen height, Haugh unit and yolk color were higher for cage eggs.
The amount of cuticle was higher in cage eggs and fluctuated with flock age in both production systems.
For the mammillary layer ultrastructural variables, a significant effect of production system and flock age was observed for early fusion, Type A bodies and Type B bodies, whereas aragonite, depression, erosion and holes were rarely observed.
Variability of mammillary cap size, the incidence of poor mammillary cap quality, incidence of late fusion, alignment, Type A bodies, Type B bodies and cubic cone formation were greater in the free-range than cage system and increased with flock age in both production systems.
The incidence of confluence and early fusion were greater in cage eggs and decreased with age in both production systems.
Significantly lower total microbial load was observed for cage eggs than from the free-range system but the overall bacterial load recorded in this study was low.
Samiullah and co-authors concluded that cage eggs were better in overall quality than free-range eggs.
Samiullah, J.R. Roberts and K.K. Chousalkar. 2014. Effect of production system and flock age on egg quality and total bacterial load in commercial laying hens. J. Appl. Poult. Res. 23:59-70. doi: 10.3382/japr.2013-00805
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