The dietary protein and lipid requirements of post-puerulus western rock lobster, Panulirus cygnus

Abstract

The dietary requirements of post-puerulus western rock lobster for protein and lipid (fat) were examined in a 6-week, pair-fed feeding study. Incremented dietary amounts of protein (30%, 35%, 40%, 45%, 50% and 55%) at each of two dietary fat levels (6% and 10%) were examined. An additional diet of fresh mussels ( Mytilus edulis) was included as a reference. At the end of the 6-week growth experiment, growth of the rock lobsters was better when protein levels were greater than 50% of the diet. Growth of rock lobsters was also significantly greater in diets with the lower fat levels. The growth of the animals fed the reference diet was significantly superior to all of the experimental diets. Survival of animals in all treatments was equal to or greater than 75%. Though there were some significant differences in survival among treatments, this was not consistent with any relationship between either protein or fat content of the diets. The number of moulting events observed in each of the test treatments was significantly lower than that observed by the mussel-fed animals. This was consistent with what was observed with the level of growth difference among the test treatments and the mussel-fed treatment. There were no significant differences in the number of moulting events among any of the protein-lipid level treatments. There were no significant differences among the test treatments with feed intake on a proportion of body weight basis. This was in accordance with the pair-feeding protocol of this study. Feed conversion by the lobsters in each of the test treatments was in accordance with what was observed in their corresponding growth responses. Diets containing 6% fat and either 50% or 55% protein had significantly lower FCR values than all other test diets (2.7:1 and 2.5:1, respectively). The diet that had 10% fat and 30% protein had the highest FCR (7.6:1) and was significantly higher than all other diets. There were no other significant differences in feed conversion among the test treatments. The results of this study support that post-puerulus Panulirus cygnus have a very high dietary protein requirement and a poor capacity to utilise dietary lipid. It should be noted though that the relative growth of the post-puerulus P. cygnus fed the pelleted diets was considerably lower than of those fed the reference diet of fresh mussels. Accordingly, optimal diets derived from this study should be based on fat levels of about 6% and protein levels equal to or exceeding 55%.