Fontes e granulometria do calcário nas dietas inicial e crescimento de frangos de corte

Abstract

The objective of this study was to study the influence of different sources of calcitic limestone associated with different particle sizes on performance, carcass characteristics and bone parameters in broilers in the initial and growth stages. It total of 1224 chicks of the Cobb -500 Slow Feather straine was used of 8 to 21 days of age and 504 at 33 to 42 days. The birds were distributed in a completely randomized design in a 3x3 factorial arrangement (three limestone sources and three granulometries), resuting in nine treatments with four replications, of 34 birds of 8 to 21 and 14 birds of 33 to 42 days. For both phases, the limestones were identified by the origin as A, B and C and contained 34, 42 and 36% of calcium, respectively. For the 8 to 21 days period the limestone granulometry were: fine (0.419 mm), commercial (1.418 mm) and hail (2.334 mm) and for the second phase the fine particle size was replaced by the coarse particle size (2.695 mm). The geometric mean diameter, geometric standar deviation, solubility of the limestone sources, performance, carcass characteristics, economic indexes and bone parameters of the tibia were determined. In the initial phase the sources of limestone presented different solubilities (P≤0.05) as a function of the granulometry and the origin of the limestone. There was no interaction effect (P> 0.05) between the sources and limestone particle size in the two phases, however, source C and hail particle size dicreased feed intake and improved feed conversion. In the growth phase, there was no interaction effect between the source and the limestone granulometry (P<0.05). The source C of the limestone decreased the consumption of the chickens, while the coarse particle size improved the feed intake and feed conversion (P≤0.05). The economic performance of the chickens was better with limestone A and the granulometry of hail in the initial diet and the coarse particle size in the diet of the growth phase. Exception of the seedor index at 42 days, the other bony parameters were not influenced (P> 0.05) by the interaction between sources and granulometry of limestones. The limestone A and C and the particle hail size of initial phase and the coarse particle size in the growth phase are more indicate for chickens. Suggest to use limestone with solubilitys of 44.84% for chickens in the initial phase and of 31,13% in the growth phase.