Evaluation of two freshwater macrophytes, Ceratophyllum demersum and Potamogeton amplifoliusas feed ingredients for Nile tilapia (Oreochromis niloticus) fingerlings
The present study was carried out to evaluate the potential of two common freshwater macrophytes (Ceratophyllum demersum and Potamogeton amplifolius) as feed ingredients for Nile tilapia fingerlings, in two consecutive experiments. The first experiment investigated the use of raw, dried C. demersum and P. amplifolius as sources of energy in the diets of fingerlings. The macrophytes were incorporated in 6 isonitrogenous and isocaloric diets at four levels as a replacement of dietary wheat bran. The test diets were fed to triplicate groups, stocked in 140 L culture aquaria in a recirculating system, three times a day to satiation, for 45 days. The results showed that control, macrophyte-free diet produced significantly improved growth rates and feed utilization efficiency than macrophytes-based diets.
In Experiment 2, fermented C. demersum and P. amplifolius were incorporated into six isonitrogenous and isocaloric diets. The diets were fed to triplicate groups of fingerlings (35 g) for 45 days. Growth rates and feed utilization efficiency of fish fed with fermented P. amplifolius at 33 % and 66 % inclusion level were not significantly different from fish fed the control diet. At 100 % inclusion level, fish performance was significantly reduced. On the other hand, fermented C. demersum produced extremely poor performance, compared to raw ceratophyllum. In conclusion, the present results indicated that fermentation improved the quality of P. amplifolius; but not C. demersum.
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