Abstract
Two experiments tested the effect of a bacterial 6-phytase (PhyG) supplemented to a vegetable broiler diet without or with added trace minerals (TM), on growth performance and TM utilization. Each tested 12 treatments in a 2 × 6 factorial arrangement with 3,360 Ross 308 males (35 birds/pen, 8 pens/treatment) in a randomized complete block design. Phytase levels comprised no PhyG or PhyG at 2,000, 1,500 and 1,000 FTU/kg during 0 to 10, 10 to 20 and (Experiment 2) 20 to 35 d of age, respectively; TM diets comprised: no added TM (diet 1); 10, 15, 3 and 10, or 20, 30, 6 and 20 mg/kg of Zn, Fe, Cu and Mn as sulphate (diets 2 and 3); 15, 3 and 10 mg/kg of Zn, Cu and Mn as oxide and 15 mg/kg Fe as sulphate, or 30, 6 and 20 mg/kg of Zn, Cu and Mn as oxide and 30 mg/kg Fe as sulphate (diets 4 and 5), and; 10, 3, 15 and 10 mg/kg of organic Zn, Cu, Fe and Mn (diet 6). Apart from no added TM, basal diets were nutritionally adequate; phytase-supplemented diets were reduced in Ca and retainable P. All diets were pelleted and fed ad libitum. In both experiments during all phases there were interactions (P < 0.05) between phytase and TM on BW, BW gain (BWG), feed intake (FI), FCR (experiment 2 only) and tibia Zn. Without phytase, TM improved (P < 0.05) these measures. Phytase without TM increased (P < 0.05) d 35 BW, overall BWG and FI, equivalent to or beyond the level achieved by TM without phytase. Tibia Zn at d 10 and 20 in Experiment 2 was increased by phytase beyond the level achieved by TM without phytase (P < 0.05). Phytase also increased (P < 0.05) liver Zn, Fe, and Mn at d 10 and 20 and plasma Zn at d 20 d. There was no consistent effect of TM source or dose on bird responses. In conclusion, PhyG phytase replaced the effect of added TM on performance during 0 to 35 d of age and could support a reduction in commercial dose levels of added TM in all-vegetable broiler diets.