Resumen
To evaluate the effect of exogenous phytase (Ronozyme HiPhos-L, produced by the strain of Aspergillus oryzae), 1050 one-day-old Ross-308 broilers with an initial average body weight of 50.29 ± 0.98 g were randomly assigned to one of seven dietary treatments with 10 replicates and 15 chicks/cage. During starter (d 1?7), grower (d 8?21), and finisher (d 21?35) periods, broilers were allowed to feed: positive control (PC), negative control (NC), and NC diet supplemented with 250, 500, 1000, 1500, and 3000 U/kg of phytase. Broilers fed NC diet supplemented with graded levels of phytase (250 U/kg to 3000 U/kg) showed a linear increase (p < 0.05) in body weight gain and feed intake during the starter and the overall trial period with no adverse effect on feed conversion ratio. The nutrient utilization of broilers showed neither an increase nor a decrease with the PC and NC diet until d 35 but when the NC diet was supplemented with a graded dose of phytase, the broilers showed a linear increase (p < 0.05) in dry matter, gross energy, calcium (Ca), ash, and phosphorus (P) utilization and a tendency to increase (p < 0.10) nitrogen retention at the end of the starter phase. Unlike the starter phase, broilers fed the PC diet showed increased (p < 0.05) ash and Ca retention at the end of the grower and finisher phase compared to those fed the NC diet. In addition, the phytase group showed a linear increase (p < 0.05) in ash, Ca, and P utilization at the end of d 21 and 35. Moreover, the inclusion of graded levels of phytase in the NC diet showed a linear increase (<0.0001) in bone (ash, Ca, and P) mineralization in broilers. Also, they showed a linear increase (p < 0.05) in gizzard weight, breast muscle, color of lightness, redness, and pH and a decreased cooking loss and drip loss. Though the standard diets were able to compensate for the P deficiency and promote performance and bone mineralization, the elevated (1000 FTU/kg) levels of phytase in the NC diet showed a higher response. Thus, we suggest that incorporating the exogenous enzyme phytase into the broiler feed in excess of 1000 units (U)/kg would be more beneficial to achieve better productivity.