Context: Reducing the environmental impact of animal production is becoming a really hot topic, especially with raised concerns over excessive flows of nitrogen and phosphorus (P) to the environment. Aims: The present study was conducted to determine the effects of phytase supplementation on growth, plasma biochemistry, bone mineralisation and P utilisation of pre-lay pullets fed varying levels of non-phytate P. Methods: A total of 240 Lohmann pullet chicks were randomly allocated to one of six dietary treatments with eight replicate cages (5 birds per cage) per treatment. Six treatments included three phytase-free diets and three diets supplemented with 1000 U/kg phytase; the non-phytate P levels were 2.75-2.50-2.25, 3.75-3.50-3.25 and 4.75-4.50-4.25 g/kg in the former, and 1.75-1.50-1.25, 2.75-2.50-2.25 and 3.75-3.50-3.25 g/kg in the latter, for the age of 0-4, 4-8 and 8-16 weeks respectively. Key results: No significant differences were found for growth performance, plasma biochemistry (calcium, P, alkaline phosphatase and albumin) and bone mineralisation among dietary treatments, but P retention (%) was different (P < 0.001). Analysis of planned contrasts showed that phytase supplementation increased phytate P retention (P < 0.001), and improving the utilisation of phytate P tended most efficiently under low P conditions. Total P retention rate was reduced slightly by phytase supplementation (P < 0.05). Conclusions: The results indicated that dietary non-phytate P level could possibly be reduced to 1.75, 1.50 and 1.25 g/kg for 0-4, 4-8 and 8-16 weeks of age respectively after phytase supplementation, without compromising pullet growth and performance during the pre-laying period. Implications: The results of this study will contribute to decreasing P excretion by poultry and reducing the potential environmental impact with land application of manure. [ABSTRACT FROM AUTHOR]
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