Response of the black tiger shrimp, Penaeus monodon to feed containing the lupin alkaloid, gramine

Abstract

In this study we have examined the effect of the lupin alkaloid, gramine, when it has been added to a feed for the black tiger shrimp, Penaeus monodon. Alkaloids provide many plants with a degree of protection against insect pests and are among the anti-nutritional factors that can limit the use of legumes in aquaculture feeds. Gramine is the predominant alkaloid in a number of important cultivars of yellow lupin (Lupinus luteus), including the Australian cultivar Wodjil. However, the total alkaloid content of Wodjil is very low and, hence, it is particularly susceptible to insect damage, especially from aphids. Australian plant breeders are interested in increasing the gramine content of Wodjil to a suggested maximum level of 500 mg kg−1 in the seed, to provide better protection for the crop. If the gramine content of L. luteus seed was increased to this level and the kernel meal was included in a shrimp feed at a maximal level of 500 g kg−1, the concentration in the feed would be less than 250 mg kg−1. In this study, we have examined the effect of dietary gramine concentrations of between 0 and 1142 g kg−1. The rate of leaching loss of gramine from the feeds was determined, and dose–response studies were carried out with juvenile P. monodon to determine the effect of dietary gramine on feeding behaviour, feed intake, growth rate, survival and digestive gland histology. Gramine leached from the feeds quite rapidly with about 20% of the gramine lost in the first hour. Dietary gramine levels of 1142 mg kg−1 significantly reduced the feed intake of the shrimp in the first 15 min after the feed was distributed in the tanks. However, over the following 5.75 h feed intake did not appear to be affected by gramine content. When examined over 50 d in a growth response experiment, the daily feed intake, growth and survival was not affected by the concentration of gramine in the feed over the range of concentrations examined. In addition, no histological changes were observed in the digestive gland of the shrimp in response to the gramine content of the feed. These data indicate that there is a significant scope for plant breeders to increase the gramine levels in the yellow lupin, cv. Wodjil to a level that will provide much better protection against aphids, without compromising its value as an ingredient in shrimp feeds.