| Abstrakt: |
This study investigated the effects of exogenous enzyme supplementation, specifically phytase and protease, in fish meal–free and phosphorus-limited diets for juvenile Litopenaeus vannamei through two feeding trials. The trials aimed to assess shrimp growth performance and apparent nutrient digestibility simultaneously in a clear-water recirculating tank system (34 ppt, 30 °C) employing a continuous feeding regime, with feces being collected on a daily basis throughout the feeding trials. In the first feeding 50-day feeding trial shrimp (3.4 g initial body weight) were fed diets supplemented with phytase (1000 and 2000 FTU/kg) and phytase together with protease (1000 FTU/kg + protease and 2000 FTU/kg + protease), in addition to animals fed a positive control (supplemented inorganic phosphate) and a negative control diet without supplementation. In the second shrimp feeding trial (4.3 g initial body weight), in addition to negative and positive controls, shrimp were fed increasing levels of phytase (1000, 2000, 3000, 4000 and 8000 FTU/kg) over a 42-day experimental period. Both feeding trials showed beneficial effects phytase addition compared to the negative control, with significant improvements (P < 0.05) observed at dietary phytase levels of 2000 FTU/kg and above. Gains were obtained in growth performance (observed weekly growth of 1.46 and 1.86 g/week for shrimp fed the negative control and diet supplemented with 3000 FTU/kg, respectively), and apparent phosphorus digestibility increasing from 41.7% in animals fed the negative control diet to 52.9% in animals fed the 3000 FTU/kg supplemented. Results indicated that phytase supplementation yielded significant improvements in shrimp growth performance and phosphorus digestibility compared to the negative control. Notably, the observed benefits were evident at specific dietary phytase levels. However, the addition of protease supplements did not demonstrate any discernible effects on shrimp performance under the experimental conditions. Overall, these findings underscore the potential of phytase supplementation as a means to enhance nutrient utilization and promote optimal growth in L. vannamei. Further investigations are warranted to explore the full range of benefits and mechanisms associated with protease supplementation in shrimp diets. [ABSTRACT FROM AUTHOR] |
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