COMPARATIVE EFFICACY OF PHYTASE FROM FISH GUT BACTERIA AND A COMMERCIALLY AVAILABLE PHYTASE IN IMPROVING THE NUTRITIVE VALUE OF SESAME OILSEED MEAL IN FORMULATED DIETS FOR FINGERLINGS OF ROHU, LABEO ROHITA (ACTINOPTERYGII: CYPRINIFORMES: CYPRINIDAE)

Background. Phytate (myo-inositol 1,2,3,4,5,6-hexakis-dihydrogen phosphate) is the main storage form of phosphorus (P) and up to 80% of the total P content in plants remains unavailable to fish due to lack of intestinal phytases for efficient phytate hydrolysis. The inclusion of microbial phytase in the feed is an approach to increase phytate phosphorus bioavailability. In the presently reported study, a comparison of the efficacy of phytase produced by fish gut bacterial strain, Bacillus licheniformis LF1 and a commercially available phytase, Biophos-TS in improving the nutritive value of sesame (Sesamum indicum) oilseed meal (SOM) was evaluated in the diet for fingerlings of rohu, Labeo rohita (Hamilton, 1822). Materials and methods. Eleven isonitrogenous (approximately 35% crude protein) and isocaloric (17.58 kJ.g(-1) gross energy) experimental diets were formulated with the same basal diet containing raw sesame oilseed meal (D1) or oilseed meal pretreated with phytase from the fish gut bacterial strain, B. licheniformis LF1 (D2-D6) and commercially available phytase, Biophos-TS (D7-D11) at 10, 20, 30, 40, and 50 FTU.kg(-1) and fed to rohu fingerlings (mean initial weight 1.85 +/- 0.52 g) for 80 days. Results. Fermentation of oilseed meal significantly reduced the crude fibre content and anti-nutritional factors tannins and phytic acid, and enhanced mineral concentration. In terms of growth, feed conversion ratio, and protein efficiency ratio, diets containing sesame oilseed meal pretreated with Biophos-TS at a concentration of 30 FTU.kg(-1) and with strain LF1 at a concentration of 40 FTU.kg(-1) resulted in a significantly (P < 0.05) better performance of rohu fingerlings. The apparent digestibility of protein, lipid, ash and minerals was significantly (P < 0.05) higher in fish fed diets D9 and D5 in comparison to those fed reference diet (RD). The crude protein, crude lipid, and ash contents of fish carcass were highest in fish fed diet D9, which was not significantly (P < 0.05) different from those in the group of fish fed diet D5. Pretreatment of diets with phytase reduced faecal P levels. Conclusion. Comparison of the efficacy of phytase produced by fish gut bacteria with commercially available phytase indicated no significant difference in performance of rohu fingerlings in terms of growth and nutrient and mineral utilization.