The seaweed, Kappaphycus alvarezii (Doty) Doty ex. P. Silva, has a high potential to be one of the key ingredients in animal feeds based on its nutritional content and commercial availability. In a previous study, 6 % of raw seaweed meal was successfully included in the diets formulated for Asian seabass (Lates calcarifer). In the present study, diets were formulated to include cooked seaweed meal at elevated levels from 6 to 22 % to investigate the effect of cooking in improving the dietary seaweed utilization. Diets with 0 % (SW0) or 6 % raw seaweed (SW6R) served as the control (CTRL) treatments. Seven experimental diets were fed to juvenile Asian seabass for 10 weeks at apparent satiation level. Diet stability and digestibility were also determined.Cooked seaweed meal performed better in term of water stability than the uncooked seaweed and water stability improved with increasing level of seaweed in the diets. Fish fed 6 % cooked seaweed (SW6) showed significantly (P < 0.05) higher weight gain and specific growth rate than other treatments and yielded the best feed conversion ratio.Except fish fed 22 % seaweed (SW22), survival (%) of experimental fish was not affected by the dietary seaweed inclusion. Dry matter apparent digestibility coefficient (ADC) ranged from 59.03 to 73.65 %. Protein ADC of the diets decreased as seaweed inclusion level increased and ranged from 68.86 to 92.05 %. Lipid ADC was not significantly different (P > 0.05) among dietary treatments. In conclusion, cooked seaweed meal at 6 % dietary inclusion level is recommended for Asian seabass.

Different types and inclusion levels of palm oil were incorporated in the enriched diets of L-type rotifer, Brachionus plicatilis, and fed to Asian seabass (Lates calcarifer) larvae. The dietary fish oil was replaced with either 50 or 75% of crude palm oil, CPO (CPO50, CPO75) and refined bleached deodorized palm olein, RPO (RPO50, RPO75). The enriched diet containing 100% fish oil (FO100) was used as the experimental control. Triplicate groups of the fish larvae of initial length 2.72 ± 0.14 mm were fed with enriched rotifer for 15 days. In general, palm oil-based enriched diets performed better than the control diet (FO100). Specifically, final mean body weight (31.3 ± 9.2 mg), final mean total length (11.5 ± 1.6 mm), SGR (29.0 ± 1.4%/day) and WG (7,769.4 ± 1,510.8%) of Asian seabass larvae fed RPO75 were significantly higher (P &lt; 0.05) compared to those fed the other palm oil-based diet and FO100. The rotifer enriched with palm oil significantly affected the body proximate composition and fatty acid profiles of the fed larvae. The present study suggests that RPO and CPO can be considered as a good alternative dietary lipid for enrichment of rotifer to positively influence the nutritional requirements of the Asian seabass larvae and support their survival and growth.

This study investigated the biochemical composition of a hybrid, crossbred between Pangasianodon hypophthalmus (PH) (♀) and Pangasius nasutus (PN) (♂), denoted as hybrid PH×PN, in comparison to its parents' species in terms of proximate compositions, fatty acid, and amino acid profiles. The results revealed that the biochemical composition of hybrid PH×PN was comparable with either one of its parents' species. The crude lipid and total saturated fatty acids (SFAs) were significantly higher in hybrid PH×PN and P. hypophthalmus. Also, crude protein and docosahexaenoic acid (22:6n-3, DHA) were higher in the hybrid PH×PN and P. nasutus. However, there were no significant differences recorded between the hybrid and its parents for omega-3 (n-3PUFA), total polyunsaturated fatty acids (PUFAs), and eicosapentaenoic acid (C20:5n-3, EPA) and (C22:5n-3, EPA). Likewise, the total essential amino acids (EAAs) was significantly higher in hybrid PH×PN and P. nasutus. In summary, certain components did not deviate much from either of their parents' species or even enhanced in the hybrid compared to P. nasutus. Therefore, the production of this hybrid could be an alternative to meet the market demand for P. nasutus.

Palm oil has been recognized as a high potential alternative dietary lipid source to reduce the reliance on expensive fish oil in aquaculture feeds. Unfortunately, most research studies were focusing on the juvenile or grow-out stage of aquatic species. This study was designed to develop weaning microdiets for Asian seabass larvae with dietary fish oil being replaced with crude palm oil (CPO) at 25, 50, and 75% (CPO25, CPO50, and CPO75) and refined bleached deodorized palm olein, refined palm oil (RPO) at 50 and 75% (RPO50 and RPO75) replacement levels. A fish-oil-based microdiet was used as a control treatment (FO100). The triplicate groups of fish larvae with initial weight and length of 1.71 ± 0.13 mg and 5.54 ± 0.34 mm, respectively, were stocked at 150 larvae/tank and co-fed with the experimental microdiets and live feeds (L-type rotifer and artemia). The final body weight (0.54–0.63 g) and specific growth rate (SGR) (12.8–13.13%/d) of fish-fed palm oil-based diets were significantly better than the control diet (0.42 g; 12.21%/day, respectively). In particular, RPO75 yielded the best SGR followed by RPO50, CPO75, CPO50, and CPO25. The feeding intake and feed conversion ratio (FCR) were not statistically different from other treatments (0.2–0.3 g/fish/d and 1.06–1.63, respectively). The survival rate of larvae-fed palm oil-based diets (33.11–46.67%) during the feeding trial was comparable to the control diet (39.33%). In the 65 ppt-salinity stress test at 25 DPH, there was no significant difference in terms of the survival rate of larvae fed the control diet and the CPO-based diets, but the lowest survival rate was observed in the RPO-based diets than the control diet. Higher final whole-body protein and lipid contents (15.3 ± 0.4 and 3.7 ± 0.0%, respectively) were observed in fish-fed CPO50 compared to other treatments. Generally, the replacement of fish oil with palm oil increased the palmitic acid (C:16:0) and oleic acid (C18:1n9) and significantly reduced the eicosapentaenoic acid (EPA) (C20:5n3) and docosahexaenoic acid (DHA) (C22:6n3) contents in both the microdiets and larval body, a common observation in this kind of investigation. Considering the good growth and survival of Asian seabass larvae in this study, availability of palm oil, and its competitive price compared to fish oil, it is suggested that weaning diets for Asian seabass larvae can be developed using palm oil as a partial source of dietary lipid.