Top‐sprayed phytase enhances the digestibility of energy, protein, amino acids and minerals, and reduces phosphorus output in Nile tilapia fed all‐vegetable diets

Abstract

This study aims to evaluate the effects of top-sprayed phytase (PHY) on the apparent digestibility coefficients (ADC) of gross energy (GE), crude protein (CP), amino acids (AA), phosphorus (P) and cationic minerals, and its impacts on nitrogen (N) and P outputs in juvenile Nile tilapia, Oreochromis niloticus. A basal diet without (Control) or supplemented with PHY at 500, 1000 and 1500 FTU (phytase units)/kg was evaluated. Data were obtained during two subsequent 10-day runs of faeces collection. Trials 1 and 2 totalled four replicates with two replicates per run. The data on initial body weight and fish age were considered in the experimental design. Compared to control group, the ADC of GE, CP, P, cationic minerals and AA increased linearly in response to the graded PHY level and were notably higher in fish fed the 1500 FTU/kg PHY diet. Moreover, in this fish, P’s ADC increased 3.9 folds and, consequently, the P output reduced from 13.83 to 5.26 g/kg body weight gain (BWG). Overall, a 1500 FTU/kg PHY can optimize energy and nutrient utilization and can be used as an eco-friendly diet for Nile tilapia.