The aim of this experiment was to determine the effects of dietary supplementation of Bio‐Mos® as a source of mannan oligosaccharide (MOS) on the growth, survival, immunity and digestive enzyme activity of freshwater crayfish, Cherax destructor (yabby). A basal diet and another diet with 0.4% of Bio‐Mos® supplemented to the basal diet were formulated. Each diet was provided to eight yabbies (35.14 ± 0.48 g, initial weight) replicated 3 times in individual 250‐L plastic cylindrical tanks for a duration of 56 days. Each tank was provided with an independent recirculating water system filtered with a biological filtration. Growth parameters such as weight, specific growth rate and average weekly gain of Bio‐Mos®‐fed yabbies were higher (P < 0.05) than yabbies fed the control diet. Total haemocyte count, granular cells and semi‐granular cells were also higher in the yabbies fed Bio‐Mos® diet. Protease activity was higher in hepatopancreas, and amylase activity was higher in the guts of yabbies fed Bio‐Mos® diet. The results implies that supplementation of MOS through Bio‐Mos® can effectively improve growth and immunological condition of yabbies.

This trial was conducted to evaluate the effects of replacing dietary fish oil with Schiz-

No abstract

Micro-algae, Schizochytrium sp., is rich source of docosahexaenoic acid, DHA (66%-lipid with 27%-DHA). Eight nutritionally balanced-diets were formulated: diet 1 (control) consisted of only fish oil (FO); diets 2 and 3 had increasing amounts of algae-meal and soybean oil (SBO) at the expense of FO; diet 4 consisted of a combination of algae meal (37-g/kg), SBO (21-g/kg), and linseed oil (LSO) at 4-g/kg each; diet 5 had microalgae meal at 50-g/kg and equal amounts of LSO and SBO at 8-g/kg; diets 6 and 7 contained equal amounts of algae-meal at 62-g/kg, but with LSO or SBO added at 8-mg/g, respectively; diet 8 contained only algae-meal at 75-mg/g. Growth and feeding efficiencies of L. vannamei were not significantly different among treatments. Fatty acid composition of muscle generally reflected that of the diet. The amount of muscle sub-epidermal adipose tissue was significantly higher for shrimp fed diets 3 and 7, while intestinal lipase was significantly higher in shrimp fed diets 7 and 8. Muscle lipid peroxidation was unaffected by the dietary treatments, although antioxidant activities were significantly higher in shrimp fed diet 7 compared to those fed diet 1. Overall algal-meal can completely replace the FO in shrimp feed.

A feeding trial was conducted to assess the effects of dietary Schizochytrium meal supplementation on survival, growth performance, activities of digestive enzymes and fatty acid composition in Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Four isonitrogenous and isolipidic diets were formulated to contain graded levels of Schizochytrium meal: 0% (S0, the control diet), 2% (S2), 4% (S4) and 6% dry matter (S6). Results showed that there was no significant difference in survival of shrimps among dietary treatments (P > 0.05). Shrimps fed diets with 2% and 4% microalgae meal had significantly higher specific growth rate (SGR) than that of shrimps fed diets with 0% and 6% microalgae meal, and no significant differences were observed between shrimps fed diets with 2% and 4% microalgae meal (P > 0.05). Activity of trypsin in the pancreatic and intestinal segments, and activity of amylase in the pancreatic segments were not significantly affected by dietary microalgae meal levels (P > 0.05). Specific activities of both alkaline phosphatase and leucine‐aminopeptidase in intestine and purified brush border membrane of intestine were significantly higher in shrimps fed diet with 2% microalgae meal (P < 0.05). There were no significant differences in C18:2n‐6, n‐3 fatty acids, n‐6fatty acids, PUFA and n‐3/n‐6 in muscle samples among dietary treatments. C16:1n‐7, C18:1n‐9, MUFA, C18:3n‐3 and C20:5n‐3 decreased, however, C20:4n‐6 increased in the muscle as dietary microalgae meal level increased. In conclusion, 4% Schizochytrium meal in microdiets of shrimps can improve growth performance and may be a valuable additive in the microdiets of shrimps.