An experiment was conducted with broilers from 22 to 33 days of age to evaluate the efficiency of six microbial phytases supplemented in diets (1500 FTU/kg) that were formulated with three different calcium:available phosphorus (Ca:P(avail)) ratios (4.5:1.0, 6.0:1.0 and 7.5:1.0). A positive control diet without phytase was formulated with a Ca:P(avail) ratio of 7.5:3.4 to meet the nutritional requirements of the broilers. The P and ash contents of the tibia, magnesium in the plasma, performance, balance and retention of phytate phosphorus (P(phyt)), intake of total P and nitrogen (N), nitrogen-corrected apparent metabolizable energy and apparent digestibility of dry matter of the diets were not influenced (p > 0.05) by the type of phytase or the dietary Ca:P(avail) ratio. However, there was an interaction (p < 0.05) between the phytase type and the Ca:P(avail) ratio for the retention coefficients of total P, Ca and N. Phytase B resulted in the highest Ca deposition in the tibia (p < 0.01). Phytases D, E and F reduced the Ca concentrations in the tibia (p < 0.01) and plasma (p < 0.05). Phytase D increased the P level in the plasma and decreased the total P excretion (p < 0.01). Phytases E and F increased Ca excretion, while phytase A reduced it (p < 0.01). Regardless of the phytase type, increasing the dietary Ca:P(avail) ratio reduced (p < 0.05) the plasma P concentration and the excretion of total P and N and, conversely, increased (p < 0.05) the plasma concentration, intake and excretion of Ca. For the rearing period evaluated, it is possible to reduce the P(avail) of the diet to 1.0 g/kg when Ca is maintained at 7.5 g/kg, and the diet is supplemented with 1500 FTU of phytase A, C, D or E/kg. This diet allows the maintenance of performance and adequate bone mineralization, and it improves the Ca, total P and P(phyt) utilization in addition to reducing the excretion of N and P into the environment.
The aim of this study was to investigate the efficiency of six microbial phytases (named of A to F) supplemented in diets (1500 FTU/kg) formulated with three different calcium:available phosphorus ratios (3.5:1.0, 5.0:1.0 and 6.5:1.0). Moreover, one positive control diet without phytase that was formulated with a calcium:available phosphorus (Ca:AP) ratio of 6.5:3.0 was also considered. The utilization of dietary nutrients, as well as the bone, plasma and performance parameters of broilers from 35 to 42 days of age was evaluated. Phytase D increased the P and magnesium plasma concentrations. Broilers fed diets containing phytase B showed a lower feed intake and weight gain, while the birds fed diets containing phytase E consumed more feed, gained more weight and excreted less total P. The highest Ca retention and also the best nitrogen utilization were determined when the diet contained phytase D or E. For all phytases evaluated, an increased in the dietary Ca:AP ratio increased the tibia ash content and the Ca balance. Phytase utilization reduced the phytate P excretion, improving its utilization by the broilers. For the rearing period evaluated, it is possible to reduce the AP of the diet to 1.0 g/kg when Ca is maintained at 6.5 g/kg, and the diet is supplemented with 1500 FTU of phytase A, B, C, D or E/kg. This diet allows the maintenance of performance, optimizes the bone mineralization, and it improves the Ca, total P, phytate P and nitrogen utilization in addition to reducing the P excretion.ARTICLE HISTORY
Resumo -O objetivo deste trabalho foi avaliar o uso de valores de equivalência da fitase como base para redução de fósforo disponível (P-disp) em dietas para frangos. Foram avaliados dez planos nutricionais com seis repetições de 15 aves cada uma. Avaliaram-se: desempenho, teor de cinzas na tíbia e custo da ração. De 1 a 7 e de 36 a 42 dias de idade, as aves receberam dieta basal; de 8 a 21 dias, dieta sem fitase contendo 3,9 g kg -1 de P-disp e quatro dietas com fitase contendo de 1,1 a 2,5 g kg -1 de P-disp; e de 22 a 35 dias, dieta sem fitase contendo 3,4 g kg -1 de P-disp mais dieta com fitase contendo 1,6 g kg -1 de P-disp. O melhor plano nutricional foi composto pelas dietas: 4,7 g kg -1 de P-disp sem fitase (1 a 7 dias); 2,0 g kg -1 de P-disp suplementada com fitase (8 a 21 dias); 3,4 g kg -1 de P-disp em ração sem fitase (22 a 35 dias); e 3,0 g kg -1 de P-disp em ração sem fitase (36 a 42 dias). A redução do P-disp ocorre no período de 8 a 21 dias de idade e corresponde a 2,0 g kg -1 de ração suplementada com fitase.Termos para indexação: avicultura, cinza óssea, desempenho, enzima, fitato, nutrição.
Reduction of phosphorus in broiler diets based on equivalency values of phytaseAbstract -The objective of this work was to evaluate the use of equivalency values of phytase as a basis for reduction of available phosphorus (aP) in broiler diets. Ten nutritional programs were evaluated with six replicates of 15 birds each. The following were evaluated: performance, tibia ash content, and feed costs. From 1 to 7 and 36 to 42 days of age, the birds received basal diet; from 8 to 21 days, diet without phytase containing 3.9 g kg -1 aP and four diets with phytase containing from 1.1 to 2.5 g kg -1 aP; and from 22 to 35 days, diet without phytase containing 3.4 g kg -1 aP plus diet with phytase containing 1.6 g kg -1 aP. The best nutritional plan was formed by the diets: 4.7 g kg -1 aP without phytase (1 to 7 days); 2.0 g kg -1 aP supplemented with phytase (8 to 21 days); 3.4 g kg -1 aP in feed without phytase (22 to 35 days); and 3.0 g kg -1 aP in feed without phytase (36 to 42 days). The reduction of aP occurs in the period from 8 to 21 days of age and corresponds to 2.0 g kg -1 of feed supplemented with phytase.
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