An experiment was conducted to evaluate the influence of two vitamin D sources and three vitamin C levels on performance, internal and external egg quality, and bone strength characteristics. In addition, the total and ionic blood calcium concentrations, bone ash and calcium were determined. Two hundred and eighty eight 23-week-old ISA Babcock B-300® laying hens were used during the 12-week study in a 2 × 3 factorial arrangement: vitamin D sources (cholecalciferol and 25-hydroxycholecalciferol - 25(OH)D3) and vitamin C levels (0, 100 and 200 ppm) resulting in six treatments with eight replicates of six hens each. The basal cholecalciferol level was 2,756 IU/kg, corresponding to 5.51 g Hy.D®/t, as source of 25(OH)D3. Feed intake, egg production, egg weight and egg mass were not influenced by the treatments. An interaction was observed for feed conversion, which was improved when 25(OH)D3 was added without vitamin C. Haugh unit and yolk index were not influenced, however, interactions were observed for albumen percent and yolk percent, which were improved when 200 ppm of vitamin C was supplemented. Egg specific gravity, serum calcium, bone ash and bone strength resistance were not influenced by the treatments. There was an interaction for shell percent and shell thickness, which were improved when vitamin C was added in association with 25(OH)D3. It was concluded, for laying hens at initial phase of egg production, that feed conversion is improved when 25(OH)D3 was the vitamin D source, and that shell thickness and shell percent are improved when the vitamin D source was 25(OH)D3 with diets supplemented with vitamin C (100 or 200 ppm, respectively).
ascorbic acid; bone strength; egg quality; performance; vitamin D
