title: Efficiency of microbial phytase supplementation in diets formulated with different calcium:phosphorus ratios, supplied to broilers from 22 to 33 days old.
abstract: 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.
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: L de P
authors.initials: LP
authors.lastname: Naves
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: P B
authors.initials: PB
authors.lastname: Rodrigues
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: L do V
authors.initials: LDV
authors.lastname: Teixeira
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: E C
authors.initials: EC
authors.lastname: de Oliveira
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: M M
authors.initials: MM
authors.lastname: Saldanha
authors.affiliation: Department of Animal Science, Federal University of Lavras, Lavras, Brazil.
authors.forename: R R
authors.initials: RR
authors.lastname: Alvarenga
authors.affiliation: Department of Chemistry, Federal University of Lavras, Lavras, Brazil.
authors.forename: A D
authors.initials: AD
authors.lastname: Corrêa
authors.affiliation: Department of Exact Sciences, Federal University of Lavras, Lavras, Brazil.
authors.forename: R R
authors.initials: RR
authors.lastname: Lima
mesh_terms: D010832:6-Phytase / Q000008:administration & dosage / Q000494:pharmacology*; D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D002645:Chickens; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D008297:Male; D010758:Phosphorus / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D010758:Phosphorus; D010832:6-Phytase; D002118:Calcium
keywords: enzyme; metabolism; performance; phytate; plasma; tibia