Different sources of microbial phytase in plant based low phosphorus diets for Nile tilapia Oreochromis niloticus may provide different effects on phytate degradation

Conclusive experimental data regarding different sources of supplemented microbial phytase in tilapia feed are very scarce. An experiment was conducted using plant based diets (24.5% soybean meal; 11.5% wheat gluten; 22.5% corn; 32.5% wheat) containing graded supply (500, 750, 1000, 1250 U/kg) of microbial phytase from two different sources (experimental phytase SP 1002; Ronozyme®P). Additionally, a negative control diet (0.41% total P; 0.15% non-phytate P; no phytase added) and a positive control diet (0.88% total P; 0.62% non-phytate P; no phytase added) were examined. Apparent nutrient digestibility (0.3% titanium dioxide as marker) was measured using six sedimentation systems (0.15 m3/system) with external sedimentation column. Triplicate groups of 10 fish (average BW 110 g) fed 3 times a day and feces collection was conducted within 4 h following each feeding period. Chyme of the proximal small intestine (hepatic loop) was sampled for measuring phytate P. In a subsequent study, blood sampling was conducted from the caudal peduncle vein (triplicates from 9 fish per diet; average BW 125 g) for monitoring of inorganic P concentration in plasma at 2, 4, 8 and 12 h following the last meal. Phytase supplementation significantly improved digestibility of protein, calcium and phosphorus. Disappearance of phytate P from the hepatic loop was significantly improved due to phytase SP 1002 and the course of inorganic plasma P concentration indicated superior release of phytate P from the plant based diet under study.