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This study was conducted to determine the effects of sago-tapioca starch ratio and moisture level of feed mixture on the physical properties of a Malaysian mahseer (Tor tambroides) extruded diet. Fifteen iso-nitrogenous diets containing varying ratios of sago-tapioca starch (20:0, 15:5, 10:10, 5:15 and 0:20) and varying moisture contents (200, 300, and 400 g/kg) were formulated. The feed mixtures were extruded using a single-screw extruder. The barrel temperature profile was set at 80-100-120 °C while the die temperature was set at 160 °C. The physical properties of extruded diets (bulk density, expansion rate, floatability, water stability, pellet durability index, sinking velocity and scanning electron microscopy) were investigated. The results showed that increasing moisture level of diet from 200 g/kg to 400 g/kg increased (P<0.05) the value of all physical properties examined. The best moisture level to produce best floating extrudates using sago or tapioca or their combination was 400 g/kg. Sago starch and combinations of the sago-tapioca starch performed as good as tapioca starch alone.

The current study was carried out to investigate the effects of replacing dietary fish oil with different vegetable oil sources and ratios on the growth performance and tissue fatty acid profiles of juvenile Tor tambroides. Three different vegetable oils (sunflower oil, linseed oil and palm oil) were used in two different substitution ratios (50% and 100%). A diet without replacement (100% fish oil) was used as a control. Triplicate groups of T. tambroides juveniles (5.0 ± 0.4 g) were fed the test diets for 9 weeks. The highest weight gain was observed in fish fed palm oil diets that, of course, were reared in aquaria. There was a significant effect (P < 0.05) of the percentage of fish oil replacement on the liver weight after controlling for the effect of fish weight (P < 0.05). The viscera weight significantly increased (P < 0.05) in fish on vegetable oil diets, and its highest amount observed among fish fed palm oil diets. Vegetable oil inclusion significantly reduced eicosapentaenoic acid and docosahexaenoic acid (DHA) concentrations in both muscle and liver of fish except for fish on 50% palm oil diet that had similar liver DHA content with those on control diet.

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The current study was conducted to determine optimal levels of dietary saturated fatty acids (SFA), n-3 PUFA and to study potential n-3 sparing effect of dietary SFA for Malaysian mahseer Tor tambroides. Juvenile T. tambroides were fed four trial diets with similar basal composition but different oil mixtures in a 2 × 2 factorial experimental design for 10 weeks. The two factors were the levels of dietary SFA and the levels of dietary n-3 PUFAs. Growth performance and fatty acid profile of tissues were analyzed at the end of the experiment. Significant differences in growth performance were observed among treatments, and fish fed the diet low in n-3 and high in SFA showed the best growth performance. T. tambroides fed the high n-3 diets showed a significantly higher (p<0.05) muscle total n-3 PUFA content compared to fish fed the low n-3 diets. The highest 22:6 n-3 and total n-3 PUFA content of the liver were also observed in fish fed the low n-3 and high SFA diet. However, the significant interaction (p<0.05) between dietary SFA and n-3 PUFA levels was observed for the total n-3 PUFA content of both muscle and liver tissues, suggesting an n-3 sparing action by dietary SFA. The results of this study suggest that 2.5% n-3 PUFA in the diet of T. tambroides, with an SFA to n-3 ratio of 15.3, is sufficient to provide the best growth performance and to retain the n-3 content of tissues.

After protein, the second major essential macronutrient in fish diet is lipid. This study was conducted to determine the optimum level of dietary lipid for the best growth performance of juvenile Malaysian mahseer Tor tambroides. Four isonitrogenous diets containing 40% crude protein were formulated to contain different levels of lipid (5, 10, 15, or 20% on an as‐fed basis). Cod liver oil was incorporated into the feed as the main dietary lipid source used to formulate the diets while residual oil coming from other ingredients contributed about 5% of dietary lipid. The experimental diets were labeled as L5, L10, L15, or L20 to denote the levels of dietary lipid. Fish were fed the experimental diets in triplicate groups for 63 d. Growth performance, survival rate, and daily feed intake by Malaysian mahseer significantly decreased when fed diets in which levels of dietary lipid increased from 5% to 20%. However, the growth performance did not vary significantly between fish fed the L5 and L10 diets. The increase in dietary lipid significantly increased the hepatosomatic index but did not influence the viscerosomatic index. Increasing dietary lipid levels also decreased the lipid content in the whole body composition of fish. The monounsaturated fatty acid (MUFA) and n‐3 polyunsaturated fatty acid (PUFA) contents of fish liver significantly increased with the increase of dietary lipid. The results of this study suggested that 5% dietary lipid is sufficient for the best survival rate and growth performance of juvenile Malaysian mahseer.

This study analysed morphology and histology of the developing mouth and digestive tract of the Malaysian mahseer larvae to assess the best weaning time to a compound diet for the fry on the basis of their morphological features. The mouth development was monitored using light and scanning electron microscopy; the development of the alimentary canal was followed histologically using light microscopy after haematoxylin-eosin staining. The larval mouth opened 1 day after hatching (1 DAH); the histological structures of oesophagus were completed by 5 DAH. At 2 DAH, differentiation of enterocytes began, and at 7 DAH the supranuclear protein inclusion appeared in the posterior intestine. The hepatopancreas was structurally completed at 4-5 DAH, coinciding with the start of exogenous feeding and the evidence of lipid storage in the liver. It was concluded that Malaysian mahseer larvae should certainly be able to ingest, and possibly digest and absorb, a formulated diet of 287 lm Ø from 7 DAH onward.

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