Three phytase preparations were added to broiler rations with considerably reduced levels of phosphorus. Birds were allocated to a positive control group (I), a negative control group (II) and three phytase-supplemented groups (III – Aspergillus niger phytase, IV – Penicillium canescens phytase, V – Pichia phytase). Major components of starter and grower diets were wheat, corn and soybean meals. Starter and grower diets (in meal form) contained 6.65 or 6.01 g of total P/kg and 3.98 or 3.68 g available P/kg in group I, and 5.67 or 5.05 of total P/kg and 2.98 g or 2.70 g available P/kg in groups II – V, respectively. This experiment, performed over a five-week period, involved Ross 308 male chickens kept in battery cages. Each group was divided into 9 subgroups, each of 9 chickens (81 birds per treatment). Phytase efficacy was evaluated based on performance results, carcass quality and bone mineralization. Optimal performance levels were achieved in group I (2.149 g body weight, 1.776 kg feed/kg gain). P reduction in group II decreased weight gains by 9% and increased feed conversion by about 5%. Diet supplementation with phytase in groups III – V compensated for the decrease in performance observed in group II. The effect exerted by three microbial phytases was similar. The difference in carcass weight between group II and the other groups was significant. P reduction in the diets negatively influenced the process of bone mineralization, which was enhanced by phytase supplementation.
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