Negative effect of phytase superdosing in laying hens

SKŘIVAN, Miloš, ENGLMAIEROVÁ, Michaela and SKŘIVANOVÁ, Věra. Negative effect of phytase superdosing in laying hens. Czech Journal of Animal Science, 2018, 63, 182-187. ISSN 1212-1819.
CathegoryScientific publication in impacted journals
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Hisex hens, aged 24 weeks, were divided into 6 groups. Each group consisted of 4 cages with 10 hens per cage with dimensions and equipment meeting the EU directives. This 2 × 3 factorial experiment included two levels of calcium (Ca; 35 or 42 g/kg) and 3 different additions of 6-phytase OptiPhos® (Ph; 0, 300, and 1500 phytase units (FTU)/kg) to the diet. The content of nonphytate phosphorus (NPP) in all diets was the same (1.8 g/kg). The experiment lasted 12 weeks. A significant interaction of Ph × Ca (P = 0.029) was observed in hen-day egg production. A diet with 35 g/kg Ca and the highest dose of Ph (1500 FTU/kg) resulted in a lower hen-day egg production (84.1%) than did the other treatments (91.5–88.6%). Phytase superdosing negatively influenced egg mass production (P = 0.001) and the feed conversion ratio (P = 0.018). Neither Ph nor Ca influenced eggshell ash content. Both additions of Ph into mixed feed decreased Haugh units (P < 0.001). A higher content of Ca in the diet increased shell thickness (P = 0.024) and shell breaking strength (P = 0.039), while Ph addition increased shell percentage (P = 0.004) and shell breaking strength (P = 0.009). The results of this experiment demonstrate the unsuitability of Ph superdosing in mixed feed for laying hens.