THE EFFECT OF A PHYTASE ADDITION IN A PHOSPHORUS-REDUCED LAYER DIET

In a trial with 10 X 180 laying hens (LSL white), the effect of Phytas e Novo L was tested on two levels (300 und 150 FYT/kg) in a phosphorus -reduced diet (diets B and C, respectively) and compared with a standa rd dirt (diet A). P-total-content for the control diets of phase 1 and 2 (21.-48. and 49.-60. week of age, respectively) were calculated as 5,6 g/kg feed and for diets B and C as 5,0 g/kg each. In phase 3 (61.- 68. week of age), the calculated P-total-contents for diets A and B/C were 5,4 und 4,8 g/kg, respectively. Due to market changes, the experi mental diets had to be transferred into diets without animal component s from week 49 up to the end of the trial. Diet A was given to two uni ts and diets B and C to four units each. All diets were fed ad libitum as crumbs and the animals were kept in a floor system. During phase 1 and 2, no diet-related differences could be seen in egg production, f ood consumption and feed conversion rare. The P-reduction of phase 3 w as followed by a decreased egg production (-5%) and a lower daily feed consumption (-6,2%); feed conversion rate was hardly influenced. The reduction of the dietary P-total-content by 0,6 g/kg in diet C led to a lower egg weight (-0,5 g) in phase 1 to 3, which was also observed i n an increase of normal eggs (53-65 g) and a decrease of large eggs (> 65 g). This effect was lowered by the supplementation of another 150 F YT phytase per kg (diet B). All the upper-mentionned differences were minimized in phase 4 (69.-80. week of age) by changing all units to th e control diet. Due to the reduction of analyzed dietary phosphorus (0 ,3 and 0,6 g/kg, respectively) and the supplementation of the phytase, P excretion was reduced for 15 and 22% with diets B and C in week 60, respectively.