Efeito dos níveis de cálcio em duas fontes sobre o desempenho de frangos de corte

Abstract

The present work was designed to verify the effect of the levels of Calcium (Ca) in two source son the performance of broiler chickens, males and females, Starbro. An experiment was carried out with levels of Ca of (0.65,0.80, 0.95, 1.10and 1.25%), and sources of Ca (calcitic limestone and calcium carbonate) in factorial design 5x2x2 (level, source and sex), with 4 replicates per treatment by utilizing 480 birds. At the end of the experiment, 2 birds per plot were slaughtered for removing the right tíbia of each, for ash, Ca and phosphorus (P) analysis. After the experimental 28-day period,four birds per plot were maintained for a balance study of Ca and P, from 29 to 31 days of age. The rations used in the experiment were formulated with 21.6% CP and 3,000 kcal/kg of ME. In the experimenta lperiod were evaluated: ration consumption (RC), weight gain (WG), feed conversion (FC),tibia ash Ca and P content, Ca:P ratio in the tíbia, tibia length and diameter; and in the balance of Ca and P: Ca and P consumption, retained Ca and P(%). An interaction (P<0.01) between level and source for RC, with a quadratic response of RC to Ca levels for, the birds fed rations containing CaCO3, obtaining the greatest consumption with the level of 0.67% of Ca in the ration. WG was reduced linearly with increasing Ca levels. FC did not present significant differences for different Ca levels utilized. Ca levels did not affect ash deposition in the tibia and Ca: P ratio in the tibias. The females which consumed CaC03-containing ration presented greater tibia ash and phosphorus content.The length and diameter of the tíbias did not suffer effects of the Ca levels, but the males presented greater diameter. Interaction between Ca levels and sex (PO.05) for Ca consumption, where the levels of Ca had aquadratic effect on the males and linear growing effect on the females. Ca retention was not influenced by the levels of Ca, nevertheless, the females which were given ration containing limestone presented increased retention (P<0.05). For P consumption by the interaction levels and sex,it was found that Males had effect from the levels, the greatest phosphorus consumption in the ration with the level of 0.88% of Ca. Where the levels of Ca had linear effect on the consumption. As to the retention of phosphorus, no significant differences (P>0.05) were observed. From the data obtained and under the conditions this experiment was conducted, it may be followed that: 1) regardless of the Ca source, the increase of the level of Ca reduced birds WG. The lowest Ca level (0.65%) do not impair performance, mineral deposition and bone growth of birds. 2)Birds fed ration containing CaCO3 reduce consumption as the level of Ca is raised in the period of 1 to 28 days of age.