Biochemical composition, amino acid and fatty acid profile changes of aquaculture feeds formulated from alternative ingredients: Long duration, storage temperature effects and ancillary FTIR confirmation

Abstract

Extrusion and non-extrusion based aquafeeds 1 and 2 are prepared. Duckweed, Spirodela polyrhiza is used as alternative feed ingredient for partial fishmeal-substitution in extruded-diet. Non-extruded fishmeal-diet is treated as control. Feeds are stored at four temperature conditions low (LT1 = −20 °C; LT2 = 4 °C), ambient (AT3), high temperature (HT4 = 45 °C). Bimonthly assessment of nutritional profile at variable temperature conditions for biochemical parameters moisture, ash, crude protein (CP), crude lipid (CL), carbohydrates (as nitrogen-free extract = NFE), gross energy (GE), amino acid (AA) and fatty acid (FA) profile is performed during six-month storage. Storage temperature, duration have significant effect (P < 0.05) on moisture, CP, CL, NFE and GE content of diets with significant decrease (P < 0.05) along assessment duration (0 to 180 days) and across storage temperatures (LT1<LT2<AT3<HT4) for CP, CL. Moisture content shows significant decrease (P < 0.05) through LT to HT condition across assessment regime for diet 1, with significant interaction effects for both diets. Significant difference in GE (P < 0.05) exists between LT and AT3, LT and HT4 for diet 1, between LT1 and HT4 for diet 2; higher GE at LT storages. Rendered oxidative, hydrolytic, thermal losses of dietary proteins and lipids is exhibited in AA, FA profiles. Significant loss from initial is noteworthy for total saturated, monounsaturated and polyunsaturated FAs (n3, n6) in both diets. Markedly, there is an overall decrease in essential, non-essential AAs. FTIR-spectra elucidates storage loss of proteins, lipids and moisture. These novel outcomes assess percentage loss of nutrients in storage diets elucidating significant nutritional profile changes. Storage at −20 °C with utilization up to two-months is suggestible for best possible dietary gains to fish and consumers. Cold-storage maintenance though may have its economic bearings specifically for small-scale farmers with limited stockpile thus storage regulation must deliberate cost-benefit values when amassing feed amounts for longer durations.