EFFECT OF ADDED PHYTASE IN LAYING HENS DI ET ON PHOSPHORUS EXCRETION AND ASSIMILATION, ZOOTECHNICAL RESULTS AND EGGS QUALITY

For this study, we realised three trials with layings hens fed or not with 600 units of phytase/kg of feed. Trial 1 : 120 hens from 22 to 48 weeks fed with a diet containing 0.6% of total phosphorus (Pt) with 0 .3% of available phosphorus (Pav). Trial 2: 120 hens from 22 to 64 wee ks fed with a diet containing 0.5% Pt (0.2% Pav). Trial 3: 120 hens fr om 49 to 64 weeks fed with a diet containing 0.4% Pt (0.1% Pav). In tr ial 1 we did not have a phytase effect on P intake, P in feces and P a ssimilation. Eggs mean weight is lower (61.62 g) with phytase (62.45 g without phytase). Trial 2, on the contrary, showed a positive phytase effect on P intake (3% more), P in feces (4% less) and P assimilation (20% more). Rate of egg production is higher as well. Trial 3 did not confirm those positive effects on P intake, P in feces and P assimila tion but showed an increase of the rate of egg production with phytase . This last one was cancelled by a lower mean weight of egg. Egg quali ty was not affected or improved by adding phytase in laying hens diet.