This experiment was conducted to evaluate the effect of levels of calcium (Ca)and particle size of limestone (LS) for laying hens. It was used 216 DekalbWhite laying hens at 25 to 49 weeks of age in a completely randomized designin a 3 × 2 factorial arrangement, composed of three levels of calcium (3.92,4.02 and 4.12%) and two particle sizes of limestone (thin - 0.60 mm; and thick- 1.00 mm), resulting in 6 treatments with six replicates of six birds. Therewas no significant effect of levels of calcium and limestone particle size neitherof the interaction calcium × particle size for feed intake, egg weight,specific gravity, shell thickness, shell percentage, Haugh unit, calcium andphosphorus digestibility and percentage of digestive tract. Production, mass,conversion by mass and conversion by egg dozen had their best results with 4.12%of calcium in the diet. Percentage of gizzard and feed intake observed at 3:00p.m. improved as limestone granulometry improved from 0.60 to 1.00 mm. Therewas an interaction effect among calcium level and limestone granulometry forbreaking strength of tibia, bone density, length of the small intestine andfeed intake at 6:00 a.m.; 9:00 a.m., 12:00 p.m., 6:00 p.m. and 9:00 p.m., respectively.It is recommended the addition of 4.12% of calcium and limestone in the thickgranulometry (1.00 mm) for a better performance of commercial laying hens. Morestudies are needed to elucidate the mechanisms involved in the alteration ofnutritional behavior of laying hens in response to changes in the levels ofcalcium and in the granulometry of limestone in the rations.
