Jirawat Tudkaew, Jacques Gabaudan, and Wutiporn Phromkunthong

pp. 17 - 24

Abstract

The effect of phytase supplementation to a low fish meal based diet on growth performance and phosphorus utilisation was investigated in sex-reversed red tilapia. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemented inorganic phosphorus and with both phytase and supplemental inorganic phosphorus.
Available phosphorus was set below requirement and the total phosphorus set to meet requirement for tilapia. After 8 weeks, there were significant differences in weight gain and protein utilisation between diets. There was an effect of phytase addition and inorganic phosphorus supplementation on bone phosphorus and whole-body phosphorus (p<0.05). A significant
effect was also observed on phosphorus digestibility, phosphorus retention efficiency and phosphorus load of the water. Phosphorus digestibility and retention efficiency were significantly (p<0.05) higher, and phosphorus load of the water was significantly (p<0.05) lower in fish fed the phytase supplemented diet compared with diets containing supplemental
inorganic phosphorus and the basal diet. In conclusion, phytase increased phosphorus availability, therefore reducing the need to add inorganic phosphorus and reducing phosphorus waste from low fish meal based diets for tilapia.