Diferentes relações cálcio: fósforo disponível e suplementação de fitases em rações para frangos de corte

Abstract

The chicken for slaughtering has low or no endogenous phytase activity. However, only a small fraction of phytic phosphorus of the diet is naturally used. Thus, the use of exogenous phytase from ration intended to these animals is crescent, because this enzyme provides greater usage of phosphorus (P). When using phytase on formulating rations with low content of P, was found to be necessary assessing the relation of available phosphorus on the diet, because this can interfere in the catalytic efficiency of the enzyme. In this work, we sought to assess the effect of different relations of available phosphorus and supplementation of two different phytases (3-phytase and 6-phytase), separated or in association, in the performance of contents of bony ashes, Calcium (Ca) and P in the tibia of chicken for slaughtering. We used 900 male-chickens, commercial line Cobb-500®, of 22 to 35 living days, using completely randomized design with ten treatments, six replications of 15 chickens in 3×3+1 factorial scheme, this representing three different forms of supplementing rations containing phytase, three relations of available phosphorus, and a diet as positive control with no phytase, formulated for attending chickens nutritional requirement. We also assessed the ration consumption (RC), weight gain (WG) and chicken feed conversion (FC). Besides, at the end of the experiment, two chicken per replication were slaughtered for extracting left tibia for further bony analysis. Data were subjected to analysis of variance and, when statistically significant, different relations of available phosphorus and different forms of enzymes supplementation were compared among themselves by using the SNK test at 5% of significance. There was no interaction between the form of phytase supplementation and the relation of available phosphorus for RC, WG, FC and content of bony ashes and Ca. Therefore, regardless the relation of available phosphorus in the diet, the 6-phytase provided the best FC. In addition, regardless the form of enzyme supplementation, the relation 7.5:1.0 also provided the best FC. There were interactions of phytase and tibia phosphorus. Thus, the enzyme 6-phytase in the proportion 4.5:1.0 and 6.0:1.0 provided greater content of phosphorus in the chicken tibia, so that we may conclude that, formulating diets using the proportion of available phosphorus on these rations and on 1500 FTU kg-1 of 6-phytase, is viable, the same way such in the proportion 4.5:1.0 for the enzyme 3-phytase, without compromising the performance and bone mineralization of fowls.