Effects of reduced calcium and phosphorous diets supplemented with phytase on laying performance of hens.

The aim of this experiment was to examine the potential for reduced environmental impact by reducing dietary calcium and phosphorus content and phytase addition of laying hen diets. A randomized complete block design with a 2x2x2 factorial arrangement of 8 dietary treatments: 2 levels ofphytase (0 and 300 FTU kg(-1)) and 2 mineral levels (Ca: 34/18 and NPP: 3.2/2.2 g kg(-1), respectively). A total of 240 White Leghorn (WL) layers, 25 weeks of age were used. Considering birds in 12 cages as a replicate, 5 such replicates were randomly allotted to each dietary treatment. Individual body weight of the bird was recorded at the beginning and end of the experiment. Egg production on an individual basis was recorded daily and percentage hen day egg production was calculated. The cleaned eggshells were dried for 24 h, weighed and expressed as percentage of whole egg. One bird from each experimental unit were selected at random and killed by cervical dislocation at the end of the experiment and the left tibia was removed. Dried bone samples were ashed at 680 degrees C for 12 h for estimation of bone ash. The results of this experiment showed that reducing Ca and NPP (Non-Phytate Phosphorus) without phytase decreased BWG (Body Weight Gain), feed intake, FCE (Feed Conversion Efficiency), egg production, egg shell weight and tibia ash. However, phytase addition to low mineral diets completely corrected the adverse effects associated with low dietary Ca and NPP. It can therefore be concluded that reducing levels of Ca and NPP below current standards and phytase supplementation can reduce pollution potential from laying hen production without adversely affecting bird performance or welfare.