Aquafeed vol 12 issue 3 2020

A sustainable mix of free amino acids improves shrimp feeding behavior

Pierrick Kersanté, Joël Duperray, BCF Life Sciences, Guillaume Le Reste, Halieutica

Mix of free amino acids and shrimp feeding behavior Poultry keratin is a major industrial co-product. The extensive hydrolysis of this sustainable but hardly digestible protein results in an interesting mix of free amino acids (MFAA). Thanks to its richness in free amino acids, the MFAA Kera-Stim®50 (Table 1) can be considered as a possible palatability enhancer in shrimp. Such a product has already been tested in a set of trials and has demonstrated its ability to sustain growth and improve feed intake and feed conversion ratio (FCR) but the shrimp behavior was not followed. To better understand how a MFAA influences shrimp feeding activity, a trial was launched at the Kasetsart University in Thailand. A total of 432 vannamei juvenile shrimp were randomly placed into 36 aquariums filled with brackish water (15 ppt salinity). A range of three feeds with decreasing fishmeal levels (15%, 7.5% and 0%) were formulated. Each of the three diets were supplemented with 0.5% of MFAA. The product was mixed with other ingredients before pelleting (Mix Group) or coated around the pellet after shaping (Ctd Group, see the detailed experimental plan in table 2). Shrimps were fed three times per day for eight weeks. Once every week shrimp behavior was thoroughly observed by trained technicians during the second meal of the day. In each aquarium, shrimps were gathered to one end of the aquarium behind a net and a feed tray was plunged at the other end of the aquarium. When the separation between animals and the feed was removed three parameters were recorded:

- Individual attractiveness: Time (in seconds) between shrimp release and first pellet attack. - Global attractiveness: Number of shrimps eating feed after 15 minutes. - Feeding stimulant: Amount of feed eaten (in gram of dry matter) within one hour.

Results As can be seen in Figure 1, MFAA shortens the necessary time for the first shrimp to reach the pellets placed in the feed tray. This duration logically increases when the fishmeal level decreases. In all cases, MFAA significantly shortens the approach time. Figure 1 also shows that when MFAA is applied around the pellet the approach time is shorter than when MFAA is mixed with other raw materials.

The number of shrimps eating after 15 minutes is another interesting observation made during those eight weeks. Figure 2 details this parameter for the nine treatments. There was a correlation between fishmeal content and global attractiveness of the feed. In all cases, and irrespective of the fishmeal level, MFAA was able to outperform their respective controls. In this case, the application mode did not clearly influence the results. Figure 3 details the average quantities eaten in each of the 36 aquariums used for this experiment. Feed consumption was not influenced by fishmeal levels. This parameter was nevertheless influenced by the use of MFAA either applied on or in the feeds. The tendency is always the same with an increasing amount of feed eaten by the shrimps fed with AA-Ctd feed, followed by the AA-Mix group and the control group.

Conclusions This trial enabled us to clearly understand how MFAA influences shrimp feed intake. Attractiveness parameters underline the ability of the product to attract white shrimps toward feeds. This trial also shows the link between the addition of MFAA and the amount of feed eaten by the animals. Taking the behavioral model proposed by Lee & Meyers (1996), MFAA can be considered as an incitant (it facilitates the initiation of feeding) and a feeding stimulant (it supports the continuation of feeding). The information provided by this experiment concerns the mode of application of MFAA on the feeds. Coating seems to be more efficient in all the behavior parameters measured during this trial. We can hypothesize that coated MFAA better diffuse around pellets allowing a better detection by shrimp chemoreceptors. Those results position Kera-Stim®50 as an efficient functional ingredient for shrimp feed. Its ability to support feed intake in low fish meal diets is particularly interesting in the actual context.

References available on request.

Full article, including tables and charts at http://www.aquafeed.com

Pierrick Kersanté, Application Engineer, BCF Life Sciences, France. E: pkersante@bcf-lifesciences.com

Guillaume Le Reste, Consultant, Halieutica, France. E: g.lereste@halieutica.net

Joël Duperray, R&D Scientific Support and Applications Manager, BCF Life Sciences, France. E: jduperray@bcf-lifesciences.com