Title : Attractability of yeast extract coated shrimp feed
Yeast (Saccharomyces cerevisiae) extract is a rich source of peptides, free amino acids and nucleotides that may be used as a feed attractant to improve feed intake and growth in livestock and aquatic animals. The aim of this study was to evaluate the attractability of shrimp feed that had been coated with yeast extract. The experiment was done in 50-liter glass tanks with five replicates per treatment. Pacific white shrimp (Litopenaeus vannamei) juvenile (1.5 - 2 g) were stocked at 30 animals per tank, and starved for a period of 12 hours prior to the feeding trial. We divided the animals into four groups, each group was fed the following feeds with or without attractant, i.e. 10% fishmeal control diet (C), commercial shrimp feed with no attractant (T1), control diet with 4% squid liver oil supplement (T2) and control diet with 2.5% yeast extract (Flavor’s UP®) supplement (T3). The animals were placed at one end and the feeding tray at the other end of the tank, both were separated by a plastic lid. One gram of the feed was placed to the feeding tray and waited ten seconds to allow the animals to sense the attractant. The lid was then removed from the tank to allow the animals to swim to the feeding tray freely. The number of times that the animals hit the feed pellets at 1, 2, 5, 10 and 15 minutes after removing the lid was recorded. The results showed that, on average at 15 minutes exposure, the animals in the T3 group had highest hit rate (42.67 times) followed by T2 (34.33 times), T1 (25.33 times) and C groups (19.00 times). This indicated that shrimp had higher interest in feed coated with yeast extract than those coated with squid liver oil and commercial shrimp feed. In conclusion, yeast extract may be used as an attractant to increase attractability of shrimp feeds. This study also showed that yeast extract had higher performance in terms of attractability to shrimp than those of animal-based attractants such as squid liver oil and fishmeal in commercial shrimp feed.