2.3.1
Diets and whole body fish samples were analyzed in triplicate for proximate composition.
Crude protein was analyzed using a CHNSO Elemental Analyzer.
Amino acid composition of experimental diets (Table 2) was determined in duplicate using a Biochrom 30 Amino Acid Analyzer following acid hydrolysis for proteins at the University of California Davis Amino Acid Laboratory.
Lipid content in diets and fish samples was determined gravimetrically following chloroform/methanol extraction at the Southern Illinois University, Carbondale.
Frozen fish fillets were lyophilized and pulverized to determine fatty acid composition.
Reserved crude lipid samples from diets and fish fillets were analyzed for fatty acid composition (Table 3) according to standard protocols.
Briefly, crude lipid samples were subjected to acid-catalyzed transmethylation performed overnight at 50c.
The resultant fatty acid methyl esters (FAME) were separated using a gas chromatograph equipped with a flameionization detector fitted with a permanently bonded polyethylene glycol, fused silica capillary column.
The injection volume was 1.0 ul. helium was the carrier gas (30 cm/s, 205 C), and the injector temperature was 250 C.
A split injection technique (100:1) was used, and the temperature program was as follows: 50 C held for 2 min, increased to 220 c at 4 c/min, and held at 220 c for 15 min.
Individual FAME were identified by reference to external standards.