One experiment was carried to determine the nutritional requirement of calcium for broilers in the starting phase (1 to 21 days) and to evaluate the availability of this mineral in dicalcium phosphate, calcitic limestone and dolomitic limestone. Seven hundred and twenty 1-day old Avian Farm broiler chicks (360 from each sex) were used. The experiment lasted 21 days. A completely randomized design, with 12 treatments, six replications and 10 birds per experimental box (five males and five females) was used. A basal diet was formulated to meet the birds nutritional requirements, except for the calcium, that remained deficient at the level of 0.161%. The basal diets were supplemented with 0.01, 0.25, 0.50, 0.75, 1.00 and 1.25% calcium levels from calcium carbonate and two levels of calcium (0.50 and 0.75%) from each source in test: dicalcium phosphate, calcitic limestone and dolomitic limestone. The first six treatments were used to estimate the calcium requirements of broilers. To determine the calcium availability in the studied sources, the treatments with 0.25, 1.00 and 1.25% of calcium were not considered. At the end of experiment, 144 birds were sacrificed by cervical dislocation for the purpose of determining the tibia breaking strength, calcium and ash levels in their tibias. According to the biological values observed for the chickens, the estimated calcium requirements were of 1.02% for broilers from 1 to 21 days old. However, according to the tibia breaking strength, the calcium requirement suggested for broilers from 1 to 21 days of age would be 1.20%. The average values of relative calcium availability were 99.99% for dicalcium phosphate, 84.67% for calcitic limestone and 75.28% for dolomitic limestone.
calcium requirement; availability; sources; broiler chicks
