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The fast-growing tropical lobster Panulirus ornatus is a good aquaculture candidate generating increased research to develop potential feeds. We conducted a 12-week experiment, assessing growth, survival and tissue carotenoid levels of juvenile P. ornatus. Lobsters were fed either pelleted feeds supplemented with astaxanthin and containing 30, 60, 90 or 120 mg total carotenoid kg−1; or one of two fresh mussel reference feeds – blue Mytilus edulis and green-lipped Perna canaliculus. There was no clear dose response, in terms of growth rate, to increasing dietary astaxanthin content; mussel-fed lobsters had inferior growth rates. Twelve-week survival was unaffected by treatment. Whole lobster carotenoid (4.7, 16.7, 27.8 and 32.8 mg kg−1, dry matter basis) increased with increasing dietary astaxanthin; pre-treatment carotenoid was 22.2 mg kg−1. Apparent total carotenoid content of the mussel-fed lobsters was unexpectedly high because of interference by other pigments. High-performance liquid chromatographic analysis of free astaxanthin levels varied from a pre-treatment value of 7.3 mg kg−1 to 2.0, 7.6, 12.5 and 23.6 mg kg−1 with increasing dietary astaxanthin, and 3.5 (green-lip) and 5.9 (blue) mg kg−1 for the mussel-fed lobsters. Although dietary astaxanthin, over the investigated range, did not affect growth rate or survival, there was a dose–response increase in tissue carotenoid content and darkening of the exoskeleton pigmentation, which may have important implications for immunocompetency and marketing. These implications are discussed in the context of pelleted feed development for this species. [ABSTRACT FROM AUTHOR]

Development of a pelleted dry feed as an alternative to feeding fresh fishery by-catch is an environmental priority for tropical spiny lobster aquaculture. Earlier studies have shown the lobster's acceptance of pelleted dry feed diminishes rapidly after immersion in water. In this work, we quantified the rate at which dry matter, total protein, soluble protein and individual and total free amino acids were lost from pieces of green-lipped mussel Perna canaliculus, a commercially-extruded Penaeus japonicus (kuruma) shrimp feed (KSF) and four laboratory-made, fishmeal-based, pelleted feeds upon immersion for up to 7.5 h. The laboratory-made feeds contained homogenates of either green-lipped mussel, polychaete ( Marphysa sanguinea), prawn ( Metapenaeus bennettae) or squid ( Sepioteuthis spp.). After being immersed in water for 0, 2.5 or 5 h, these same feeds were offered as a paired choice with KSF in two preference feeding studies with juvenile Panulirus ornatus lobsters. The loobster's preference for fresh mussel always exceeded that of KSF, irrespective of immersion time. Regression of the proportional intake of test feeds against the relative leach rate of KSF identified soluble protein, glycine and taurine as the principal leachate components having the highest positive correlations with the lobster's feeding preference. [ABSTRACT FROM AUTHOR]

The inclusion in feed formulations of ingredients that act as attractants and feeding incitants or stimulants has been proposed as a means of increasing feed consumption, and hence growth, of farmed shrimp. Squid, crustacean and krill meals, fish and krill hydrolysates and a betaine product (Finnstim) were examined to assess their relative effectiveness in increasing the feed intake of black tiger shrimp Penaeus monodon. These presumed feeding effectors were added to a base feed at between 5 and 50 g kg−1. Given a choice between the base feed and one containing one of the test ingredients, P. monodon showed a significantly greater preference for the feeds containing crustacean or krill meal. Four of the presumed feeding effectors were further evaluated in a growth response experiment. There was no significant difference in the amount the shrimp consumed of any of the feeds. However, the growth rate of the shrimp was about 20% faster on the feeds containing crustacean meal or krill meal. Although ingredients such as crustacean meal or krill meal can improve feed intake, in practical feed formulations that contain significant amounts of terrestrial protein but relatively low levels of marine ingredients, there does not appear to be need for additional feeding effectors. However, crustacean meal and krill meal do provide a significant nutritional benefit, as seen by the improved growth rates in this study. [ABSTRACT FROM AUTHOR]

In this study we tested the hypotheses that higher fat diets will promote greater fat oxidation, and that medium-chain fatty acids (MCFA) will be more readily oxidized than long-chain fatty acids (LCFA). The oxidation of dietary MCFA (coconut oil labelled with14C-octanoic acid) and LCFA (olive oil labelled singly with14C-palmitic acid and14C-oleic acid) was measured in a metabolic chamber. MCFA and LCFA were included in the respective diets at 150 and 300 g kg−1. Polka dot grouper fed diets containing MCFA had a significantly higher (P < 0.05) respiration rate [2.4 mmol CO2 BW (kg)−0.79 h−1] and proportion of radioactivity in the respired CO2 (49.5%) than those fed diets containing LCFA [1.2 mmol CO2 BW (kg)−0.79 h−1 and 12.8%, respectively]. The amount of dietary fat did not significantly affect either of these two response attributes. The radioactivity in faeces and regurgitated material was low with diets containing MCFA, but was significantly higher with diets containing LCFA, and increased with increasing LCFA content, suggesting a decrease in digestibility. These results show that MCFA provide this species with a more readily utilizable source of energy than LCFA. Moreover, raising the amount of lipid in the diet above 150 g kg−1 did not increase the oxidation of fatty acids for energy. [ABSTRACT FROM AUTHOR]