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.

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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. KEY WORDS

A series of experiments were conducted with black tiger shrimp (Penaeus monodon) juveniles to firstly determine the effects of reducing fishmeal inclusion in a diet and then to evaluate the potential for a microbial bioactive to support complete replacement of both fishmeal and fish oil in feeds when fed under clear-water and green-water conditions. The isoproteic and isoenergetic replacement of fishmeal resulted in a consistent decline in growth performance indicating that at every decrease in fishmeal below an inclusion level of 45% there was a decline in performance. In a subsequent trial undertaken in a clear-water tank system diets devoid of both fishmeal and fish oil fed to shrimp were demonstrated to produce poorer performance than a fishmeal and fish oil reference diet. However the addition of a microbial bioactive to the diet resulted in not only a compensation for the replacement of these ingredients but additional growth. Replication of the clear-water trial in a green-water tank system produced similar results, but also showed that the green-water system largely compensated for the performance lost through replacement of fishmeal and fish oil. However it was also shown that the use of the microbial bioactive in the diets still resulted in improved growth performance of shrimp. This study has effectively demonstrated a viable strategy for not only a complete replacement of all fishery products in shrimp diets, but an improved performance strategy.