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This study was carried out to investigate the effects of different none phytate phosphorous
(nPP) levels and phytase supplementation on performance in broiler chicks. Ross® straight-run
broiler chicks (n=576) were allocated to six dietary treatments, each replicated three times (32
chicks per pen) in a completely randomized design and in a 3×2 factorial arrangements. Three
dietary phases were employed, a starter (0-20d), grower (21-40d) and finisher (41-51d). During
the experimental periods, the chicks were fed with diets of different nPP levels (0.45,0.38, and
0.31% during starter period, and 0.43,0.36, and 0.29% during grower and finisher periods), with
and without 500 F.T.U phytase (Natuphos 10000). Measurements included body weight (BW),
daily gain (DG), feed intake (FI) and feed conversion ratio (FCR). The results indicated that nPP
levels, did not have any significant effect on broiler performances during starter period, but
chicks fed with 0.29% NPP diets, had a significantly lower BW at 40d and 51d,as well as a
lower D.G during 21-40 and 1-51d growth periods. Feed intake was not affected by nPP levels.
FI ( 1-20, 20-40d , and 1-50d) and FCR(1-20d) significantly increased with phytase addition to
the diets. The effect of interactions between nPP levels and phytase supplementation on BW at
41d was significant, so that the BW in chicks fed with low NPP containing diets was improved
by phytase, whilst BW in chicks fed with high NPP containing diets was adversely affected by
phytase supplementation. In conclusion, the results indicated that the negative effect of feeding
low NPP diets becomes most evident after 21d of age, and phytase addition to the diets fails in
returning performances back to those in the control groups. Further studies are needed to
determine the proper NPP levels and phytase dosages during different growth periods.