Effects of dietary mannan oligosaccharide supplementation on juvenile spiny lobster Panulirus homarus (Palinuridae)

Abstract

Dietary supplementation with mannan oligosaccharide (MOS) has been demonstrated to provide significant benefits to growth and health of many species of fish and crustaceans. An investigation was made to assess the effect of MOS supplementation on the diet of the tropical lobster Panulirus homarus. The aim of the study was to test the effect of various dietary inclusion levels of MOS on growth, survival rate, intestinal morphology and bacterial abundance, haemocyte make-up, and tissue composition of P. homarus lobsters. A manufactured, semi-moist diet was used as a basal diet and supplemented with 0.2%, 0.4%, 0.6% and 0.8% MOS inclusion, and fed to lobsters with an initial mean weight of 0.16 g for 56 days. A typical fishery bycatch mixture was used as a reference control diet. Growth rate of lobsters was significantly higher for those fed diets supplemented with 0.4 and 0.6% MOS than those fed an un-supplemented diet or bycatch. Survival rates of lobsters ranged from 68 to 78%. The survival rate was significantly higher in lobsters fed diets with 0.2% and 0.4% MOS supplementation and bycatch, compared with those fed the basal or 0.6% MOS diet. There was no significant difference in differential haemocyte count of lobsters fed with various MOS levels or bycatch. The mid-gut surface area of lobsters fed diets supplemented with 0.2%, 0.4% and 0.6% MOS was significantly higher than that of lobsters fed on control, 0.8% MOS or bycatch. The total Vibrio count in the mid-gut of lobsters fed any MOS diet was significantly lower than that of lobsters fed either the control or the bycatch diet. There was no significant difference in protein, lipid or ash content in lobsters fed the different diets. There were significant correlations between concentrations of MOS in diets and lobster growth rates. Optimal MOS concentration was estimated to be 0.69% at day 14 (R2 = 76.79%), 0.55% at day 28 (R2 = 88.18%), 0.48% at day 42 (R2 = 97.72%) and 0.47% at day 56 (R2 = 94.42%), demonstrating a decreasing requirement for MOS with increasing lobster size. In conclusion, mannan oligosaccharide supplementation appears to be effective for improving growth, survival and gastro-intestinal health of the lobster, P. homarus.