The effect of milling method, thermal treatment, and particle size of feed on exterior and interior egg quality in laying hens

Abstract

Summary Various milling methods, thermal treatment and particle sizes are used in feed production for laying hens, which may influence egg quality. The present study was designed to investigate the effect of feed produced by roller (R) and hammer mill (H) as mash (M) and expandate (E) with coarse (C) and fine (F) particle size on exterior and interior egg quality in layers. A total of 240 hens (Lohmann Brown), 19 weeks old, were used in a randomized design with 2×2×2 factorial arrangement. Eight experimental diets were offered ad libitum during the whole experimental period and one week before for diet adaption. Eggs were analyzed for egg weight, area, shape index, shell weight per unit surface area, air cell, yolk color, blood spot, Haugh unit, yolk and albumen measures (weight, index, height, width and length) shell measures (stability, surface area, density, thickness and membrane weight), and percent contents of yolk, albumen, shell and shell membrane. The shell membrane weight and percent shell membrane weight was lower in treatment H as compared to treatment R ( P<Â 0.01 and P≤0.01, respectively). Thermal treatments displayed higher percent shell membrane weight in treatment E than treatment M ( P≤0.04). The shell density was higher in treatment F in comparison with treatment C ( P≤0.04). The shell thickness and shell weight were higher in treatment C as compared to treatment F ( P≤0.02 and P≤0.04, respectively). The interaction between milling methods and particle size affected shell thickness ( P≤0.01). Milling method influenced yolk index and yolk height, which were higher in treatment H as compared to treatment R ( P<Â 0.01 and P≤0.02, respectively). The albumen height was higher in treatment C than treatment F ( P≤0.03). The interaction between milling method and particle size affected blood spot, albumen length and yolk height ( P≤0.05, P≤0.04 and P≤0.04, respectively). The interaction between thermal treatments and particle size affected yolk color ( P≤0.04). Additionally, percent albumen weight was affected by interaction between milling methods, thermal treatments and particle size ( P≤0.05). In conclusion, most of egg quality parameters of economic importance were not affected by the treatments used in present study. Therefore, milling method, thermal treatment and particle size of feed seem to be of lower importance for layer feed production regarding the optimized egg quality.