The objectives of this study were, to produce phytase on large scale and to make sure its effectiveness in utilization of phytate P in diet of growing pullets. The fungal species Aspergilus niger was used as fermentation organism, for the production of extra cellular high active phytase enzyme on defatted rice bran through solid state fermentation (SSF). Cultivation conditions for phytase production including substrate; water ratio, temperature, were optimized. Phytase production was found maximum after 96 hrs of incubation, at 40% moisture level. The developed conditions were then utilized for production of phytase on large scale basis. After production, the activity of enzyme was measured. Then this phytase was supplemented to layer grower negative control diet (NPP 0.3 1%) in different proportions i.e., 0, 1000, 1500 and 2000 tg/kg of diet to increase the bioavailability of phosphorus. Rice polishing was used as a major ingredient, as it contains high phytate contents. During experiment, feed intake, weight gain and FCR of birds were measured on weekly basis. Excreta were collected at the end of experiment to determine the effect of phytase on P availability. Also samples of toes were collected and percentage toe ash was measured.

The total feed consumption from 9-18 wk of pullets fed on diet A, B, C and D was 2919.7, 2861.9, 2913.6 and 2930.9g respectively. Weigh gain was 743.15, 718.37, 749.70 and 768.OOg respectively and FCR was 3.93, 3.99, 3.89 and 3.81 respectively.

The results showed that when low P diet (0.31% NPP) was supplemented with different levels of phytase, there was slight improvement in the performance of birds with the addition of phytase in respect of feed consumption, weight gain and FCR. Group "D", fed with diet containing 0.31% non phytate phosphorus (NPP) plus phytase (2000 igfKg of diet) showed best performance than all other groups. Group "B", fed with diet containing 0.3 1% NPP plus phytase (1000 j.tg/Kg of diet), showed poorest performance. While the performance of group "C", fed with diet containing 0.3% NPP plus phytase (l500.ig/Kg of diet) was almost similar to control group (A) fed with diet containing 0.4% NPP without phytase. The data was subjected to statistical analysis, using completely randomized design (CRD). The statistical analysis revealed non-significant difference (P> 0.05) among all treatments in respect of feed consumption, weight gain and FCR. The results were non-significant; it indicates that even lowest level of phytase (1OO0tg/Kg of diet) with 50% DCP was sufficient to maintain optimum performance of pullets. It also indicates that further investigations are required to decrease the DCP level below 50% with addition of different levels of phytase.

Phosphorus availability percentage of groups A, B, C and D was 42.67, 50.00, 54.68 and 60.67% respectively. While percentage of toe ash was 11.9, 11.2, 12.1 and 12.7% respectively. The results of P availability measured from the P intake through feed and P voided through feces showed that there was significant linear increase (P < 0.05) in percentage of P availability with increase in level of phytase. In group D (2000ig phytase 1Kg of diet) there was highest availability of P while in control group there was lowest availability of P.

In respect of toe ash there was significant difference (P < 0.05) among different experimental pullet groups. Highest toe ash percentage was in D (2000.tg phytase /Kg of diet) group while lowest in group B (l000.tg phytase /Kg of diet). Toe ash percentage of group C (1 500.tg phytase 1Kg of diet) was slightly better than group A (control). Statistically groups A and C were better then group B, but non-significant among each other. Toe ash was higher (P < 0.05) in group D than all other groups except group C.

Conclusion

- We can reduce 50% of inorganic source of phosphorus i.e. DCP with the addition of phytase, in the diet of growing pullets, with out any adverse effect on the performance of pullets.

- Other benefit of phytase supplementation is that we can improve availability of P and ultimately can reduce P in feces of birds and thus can reduce the environmental pollution.

- Further investigations are required to reduce DCP level more than 50% or even up to 0 levels with the addition of phytase.