Effects of a low-phosphorus diet and exogenous phytase on performance, egg quality, and bacterial colonisation and digestibility of minerals in the digestive tract of laying hens

The objective of the experiment was to determine the effects of different levels of phytase (0, 150, 250, and 350 phytase units (FTU)/kg; F) produced by Aspergillus niger in the diets of hens fed decreased contents of non-phytate phosphorus (1.8 and 2.1 g/kg; NPP) on the hen performance, egg quality, digestibility of calcium and phosphorus in the ileum, and representation of bacterial species in the ileum and caecum. The diet with 2.1 g/kg of NPP and 350 FTU/kg significantly decreased egg weight (P < 0.001) and egg mass production (P < 0.001). However, this treatment had the highest values for shell percentage (P = 0.002), shell thickness (P = 0.006), and shell index (P = 0.003). The supplementation with F at 350 FTU/kg to the diet with 1.8 g/kg of NPP increased the shell quality to a level that was comparable with the eggs from the hens fed the diet with only 2.1 g/kg of NPP. With the addition of F (350 FTU/kg) to the mixed feed with 1.8 g/kg of NPP, the digestibility of calcium and phosphorus in the ileum increased by 6.1% and 7.4%, respectively, although the increases were not significant. Additionally, the frequency of Lactobacillus spp. was higher in the ileum and caecum of hens fed the diet enriched with F than in those fed a diet without F addition. The dietary manipulations with NPP and F improved some performance and shell quality characteristics, and the addition of 3-phytase at a level of 350 FTU per kg to the low-P diet increased the digestibility of minerals and changed the microflora of the digestive tract.