ASSESSMENT OF DIGESTIBILITY OF SELECTED FEED INGREDIENTS FOR FINGERING SNAKEHEAD FISH (Channa striata) USING  IN VIVO AND IN VITRO METHODS

Snakehead fish (Channa striata) has become an economically important cultured freshwater fish in Thailand. The total production reported for this species to FAO for 1999 was 32,938 t. The countries with the largest produce were Thailand (27,500 t) and Philippines (5,438t) (FAO, 1999). Many farmers still use trash fish in preparing feed at the snakehead fish farm. From feeding trash fish, all nutrient leaching from trash fish and effect on water quality from uneatable feed. Knowledge of nutrient digestibility of the various feed ingredients used in formulating fish feeds is desirable so that effective substitution of one ingredient for another may be achieved. No information is yet available on the apparent digestibility of nutrients for snakehead fish in Thailand. The objective of this study was to determine apparent digestibility of nutrients in selected feed ingredients for snakehead fish.

Apparent digestibility of nutrients of three feed ingredients: fish meal (FM), soybean meal (SBM) and poultry meal (PM) were determined by incorporated of test ingredients to practical reference diet at a 7:3 ratio (70% of reference dietand 30% of test ingredient described by NRC, 2011). Chromic oxide (Cr₂O₃) is used as external digestibility marker at 0.5% in feed formulation.

The protein digestibility for fish meal was 84.51%, poultry meal was 77.17%  while that for soybean meal was only 64.41%. The fat digestibility for fish meal was 81.26%, poultry meal was 66.84%  while that for soybean meal was 54.95%.

The results shown that snakehead fish have the tendency to digest protein in feedstuffs of animal origin more efficiently than protein in feedstuffs of plant origin.

In vitro digestibility of different feed ingredients was investigated using an enzyme extract from whole digestive tract. The digested protein was determined as liberated reactive amino groups of the peptides using the trinitrobenzenesulphonic acid (TNBS) method. The concentration of the reactive amino groups was calculated using DL-alanine as a standard.

Studies of in vitro protein digestibility of different feed ingredients indicated that FM and PM are suitable ingredients for a formulated feed for fingering stages.

In conclusion, data presented here suggest providing information on nutrient digestibility of feed ingredients used in complete feed for snakehead fish.