Dietary inorganic phosphorus or microbial phytase supplementation improves growth, nutrient utilization and phosphorus mineralization of juvenile red sea bream, Pagrus major, fed soybean-based diets

A 2 x 3 factorial design with triplicates examined the interaction between dietary inorganic phosphorus (IP) and phytase on growth, mineral utilization and phosphorus (P) mineralization in juvenile red sea bream. The treatments were three levels of dietary IP supplementation at 0, 2.5 and 5 g kg-1, either without or with phytase supplementation [2000 FTU kg-1; phytase unit is defined as the amount of enzyme activity which liberates 1 micromol of inorganic phosphorus per minute at pH 5.5 and 37 degrees C at a substrate concentration (sodium phytate) of 5.1 mmol L-1]. Juvenile red sea bream (IBW = 1.3 g +/- 0.1) were stocked twelve fish per tank and fed for 50 days. Growth and feed efficiency were significantly (P < 0.05) enhanced by both dietary P and phytase supplementation. Feed intake and survival rate were not significantly affected by the dietary treatments. Both dietary IP and phytase supplementation significantly increased plasma IP and Mg levels. Concentration of vertebral mineral and scale P was significantly increased by both dietary treatments. A skeletal malformation syndrome of scoliosis occurred in fish fed both non-IP and non-phytase supplemented diet. Interaction between main dietary effects was detected for vertebral Zn, scale P and whole-body ash and Mg content. With regard to growth and other examined productivity traits, phosphorus requirement of juvenile red sea bream can be met if supplemented with 2000 FTU phytase kg-1 or in the absence of phytase, by dietary inclusion of 2.55 g kg-1 of IP.