Ciências Marinhas: Pesquisa e Desenvolvimento

Abstrato

Is Fortification of Methionine Necessary in Soya Bean (Glycine Max) Based Feeds for Oreochromis andersonii (Castelnau, 1861) Raised in Semi-Concrete Ponds?

Kefi AS, Chungu NP, Mupenda N and Mumba C

An experiment was conducted to determine the optimal amount of methionine that can be incorporated in the soya bean based Oreochromis andersonii feeds. Three levels (2%, 4% and 6%) of methionine included in soya bean based feed (30% and 10% crude protein and crude lipid respectively) were tested on O. andersonii for seventy eight (78) days in hapas erected in a semi–concrete pond (250 m2 ) arranged in a complete randomized design. Specific growth rate (SGR% day-1), mean body weight gain (MBWG) (g) and apparent feed conversion efficiency (AFCE %) differed (P<0.05) among the treatments although the 4% and 6% gave similar (P>0.05) SGR (%), MBWG (g) and AFCE (%) but higher than the control and the lowest methionine level used in the experiment. Trend analysis showed a linear relationship (F=3.358, P=0.02) between Gonadosomatic Index (GSI) and methionine level with the highest methionine level producing fish with the highest GSI. Furthermore, the highest methionine level produced a significantly higher (P<0.05) GSI than in other treatments. However, females and larger sized fish appeared to mature earlier than males and smaller fish respectively. Fish body moisture and ash were similar (P>0.05) in all the treatments. It is, therefore, recommended that soya bean based feed can be fortified with 4% methionine to improve the O.andersonii growth. An economic analysis is required to ascertain the cost effectiveness of using the synthetic amino acid in soya bean fish feeds for O. andersonii.