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An 8-week experiment was conducted to study the effect of added Natuphos® 5000 phytase in corn–soybean meal-based diets on laying hens fed different levels of crude protein (CP) (14 and 17%). Two levels of phytase enzyme were used: 0 and 600 Phytase Units (FTU)/kg feed. The experiment used 144 Hisex Brown laying hens in a 2 × 2 factorial design. Four treatments and three replicates per treatment with 12 hens per replicate were used. Egg production was recorded daily while egg weight was assessed on 13th and 14th day of each two-week period to calculate total egg mass. Total excreta were collected and approximately 10% of the amount was used for analysis after drying in a forced draft oven. The results showed no significant effect of added phytase on excreta Calcium (Ca) content, but significantly lower Magnesium (Mg) content was observed with phytase (3.54, 2.48, 3.13 and 2.75 % for hens fed 14% CP no phytase, 14% CP + phytase, 17% CP no phytase, and 17% CP + phytase, respectively). Added phytase also significantly decreased Mg excretion measured as grams/kg of egg mass (21.43, 12.47, 16.76 and 14.75 g/kg egg mass for hens of respective dietary treatments. Phytase had a strong effect on Zink (Zn) levels with 438.96, 369.17, 434.38 and 374.58 mg Zn/kg dry excreta of hens. Similar results were observed with Cu. Added phytase significantly reduced the excreta content and the excretion of Cu. The results of this experiment indicate that adding 600 FTU to laying hen diets containing 14% CP decreases the excretion of Mg, Zn and Cu without any adverse effects on the egg mass produced of laying hens.

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