Broiler breeders. Eggshell thickness. Shell area. Shell index.

This study examined the replacement of the inorganic minerals (IM) Cu, Fe, Mn and Zn with their organic form (OM) in the diet of 67-week-old Dekalb White laying hens by comparing digestibility, production and egg quality. The experiment involved 240 birds, with 48 birds used per treatment and 12 per replicate. Isoenergetic and isonutrient diets were supplemented with 8mg Cu, 50mg Fe, 70mg Mn and 50mg Zn per kilogram of diet from an inorganic premix (IM100), from an organic premix (OM100), or the latter at the decreasing inclusion levels of 65% (OM65), 45% (OM45) and 35% (OM35). The following variables were evaluated: production, eggs per housed bird (EHB), viability, egg weight and mass, cracked and lost eggs, digestibility and egg physicochemical traits. Birds fed OM35 and OM45 showed lower production rates, and organic minerals provided the highest egg weights, regardless of their inclusion level. Accordingly, egg mass was similar between IM100, OM45 and OM35, and highest values were obtained with OM100 and OM65. Source or level had no influence on digestibility or egg quality. Supplementation with 2.8mg Cu, 17.5mg Fe, 24.5m g Mn and 17.5mg Zn per kilogram of diet (OM35) in the last third of the laying cycle provided relevant economic production indices (EHB, viability, egg weight or mass).