Limestone particle size and Aspergillus niger phytase in the diet of older hens

AbstractThe aim of this experiment was to evaluate the influence of limestone particle size and phytase (F) on performance, physical egg parameters, mineral digestibility and microbial colonisation in the digestive tract in older hens aged 60–71 weeks. One hundred and sixty Lohmann Brown hens were housed in enriched cages. The 2 × 2 factorial experiment included two levels of 3-phytase NATUPHOS® (0 and 350 FTU/kg), two sizes of limestone grain (coarse limestone (CL) and a mix of CL and fine limestone (FL) (1:1)) in mixed feed. All of the diets contained 4.4 g/kg of total phosphorus and 34 g/kg of calcium. Coarse limestone with F addition significantly increased hen-day egg production (p = .018). The phytase supplement at 350 FTU/kg significantly increased shell quality characteristics. Haugh units (p = .039) and albumen index (p = .008) was higher when using the limestone mix, the same applies to yolk index (p = .013). The phytase addition to the mixed feed non-significantly increased calcium and phosphor...