Physical egg quality from organic versus conventional laying hens

The physical quality of eggs laid by hybrid hens reared under organic farming system (ORG) was compared with that of eggs laid by hybrid hens reared conventionally (CON). The ORG eggs belonged to 5 Organic farms whereas CON eggs were from floor housing (F) and cage housing (C). The eggs’ physical quality was measured on 100 eggs per each ORG, on 104 eggs of F and on 78 eggs of C groups. The albumen pH was measured within 3 days after laying. Measurements included individual whole egg weight and that of its constituents, in order to calculate their proportions. Other measurements were egg equatorial diameter, egg height and eggshell thickness. Indexes were then calculated: Shape index= (equatorial diameter/height) x 100; Surface area= 4.67 x (egg weight)2/3; Eggshell index= eggshell weight/(equatorial diameter/height). With exception of the egg Surface area, all the parameters considered were significantly affected by the farming system (P<0.001). Compared to the CON eggs the ORG eggs were heavier, had lower yolk/albumen ratio, lower eggshell thickness and eggshell weight incidence. Average Shape index value was higher in C than in ORG eggs (P<0.05) and average Eggshell index value was higher in ORG than in F eggs (P<0.05). The average albumen pH was significantly lower in ORG eggs compared to that of CON eggs (8.85 vs 9.15; P<0.001), and that of F was lower than that of C eggs (9.11 vs 9.19; P<0.05). Among the 5 farms of the ORG the eggs highlighted a large variability in the considered values and indexes, and this represents a level of criticality that should be taken into account