Thanamas Singkong. Giant Salvinia (Salvinia molesta) as a substitutional source of protein in the kibble for freshwater herbivorous fish . Master's Degree(Technology of Environmental Management). Mahidol University. Mahidol University Library and Knowledge Center. : Mahidol University, 2019.
Giant Salvinia (Salvinia molesta) as a substitutional source of protein in the kibble for freshwater herbivorous fish
Abstract:
This study aimed to develop kibble feed of Nile Tilapia (Oreochromis niloticus) and Thai silver barb (Barbodes gonionotus) by using Giant Salvinia (Salvinia molesta) as an additional source of protein instead of fish meal. Kibble feed of formula 1 (control) 2, 3, 4 and 5 contains proportion (in percentage) of S. molesta replacement of fish meal in feed formula 0, 25, 50, 75 and 100%, respectively. Nile Tilapia and Thai silver barb for this experiment had average weight 161 ± 14 g/fish and 8.61 ± 0.98 g/fish, respectively. An experiment was intensive culture and carried out in the cages in Maeklong River for three months. The results showed that average final weight and length, absolute growth rate (AGR) and feed conversion ratio (FCR) of Nile Tilapia fed with all formula were statistically significantly different (P<0.05). Average weight and length, AGR and FCR of Nile Tilapia fed with formula 2 had the closest to formula 1 (control), whereas specific growth rate (SGR) and survival rate (SR) were not significantly different (P>0.05) among formulas. The average final weight and length of Thai silver barb fed with all formula were statistically significantly different (P<0.05), average weight and length of Thai silver barb fed with formula 2 had the closest to formula 1 (control), whereas AGR, SGR, SR and FCR were not significantly different (P>0.05) among formulas. Water quality (water temperature, transparency, pH, hardness, alkalinity, DO, BOD, ammonia) in each cage of both for Nile Tilapia and Thai silver barb was in the suitable range of the standard of aquaculture. It is suggested according to the results that aquaculturist choose to consider applying fish feed mixed with S. molesta in three different criteria: (1) to consider the protein level in the kibble feed, (2) to consider the AGR and FCR, and (3) to consider the cost of production and break-even point. In this study, the results showed that fish feed formula 2 had the lowest break-even point; thus, it is recommended for culturing Nile Tilapia, but this experiment is not worth the investment for culturing Thai silver barb fingerlings, which may depend on the initial size of Thai silver barb, which is not suitable for the size of fish feed. Due to the small size of Thai silver barb, they feed on single cell algae and zooplankton. After all criteria for consideration, a proportion of 25% S. molesta of fish feed formula 2 is the most suitable to be used as a substitutional source of protein from fish meal for Nile Tilapia culture.