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Fish silage: a profitable source of protein in animal feed?

VALORISATION OF RESIDUAL FLOWS FROM THE BELGIAN FISHERY

A large part of the residues from the fish processing industry, such as heads, hides and skins, and intestines are currently under-utilised (waste/biogas). In addition, the recently introduced landing obligation will lead to an increase in volume of residual flows, mainly in the form of undersized quota species. According to the law, this new supply may not be sold for direct human consumption. The aim of this research is to find a realistic solution for the valorisation of these residual flows. The course chosen investigates whether fish silage can be used as a fishmeal substitute in animal feed and whether it is possible to produce this in a profitable way in Belgium.

CASE STUDY: FLEMISH FISH SILAGE AS A SOURCE OF PROTEIN IN SHRIMP FEED

Fish silage is considered to be an efficient technique to stabilise fish residues. An organic acid is added to the homogenized fish residues to lower the pH and create an antimicrobial environment. The body's own enzymes then hydrolyse the fish residues, resulting in a nutritional semi-liquid product that contains proteins, peptides and amino acids, among other things. Producing fish silage is a relatively inexpensive and simple process and can already be profitable with lower residual flow volumes, as opposed to fishmeal production. The aim of this research is to study the production of fish silage, to optimise it, and then to apply it as a source of protein in feed for shrimp.

RESEARCH AND RESULTS

The nutritional properties and stability of the fish silage were determined over 3 months. Results show that the fish silage is of good quality. With an average protein content of 64.3% (dry matter basis) it is comparable to the average fishmeal (65%). Fish silage is also a good source of essential amino acids and unsaturated fats. During the experiment, however, a slow decline in nutritional quality was observed. This was probably caused by the hydrolysis process, which eventually led to a loss of amino acids and unsaturated fats. In addition, the fish silage also contained a high moisture content, which makes it difficult to compete with the existing fishmeal. The results of this research have been published recently.

Data is currently being collected on the optimisation of the fish silage and the process. For this purpose, a pasteurisation step is added to limit the hydrolysis and nutritional loss in the fish silage. Also a drying step has been added. The drying of the fish silage is done using the Dry-On-Water technique, available via the Food Pilot. At the same time, experiments are also being conducted with fish silage as a source of protein in shrimp feed. To this end, fishmeal is replaced to varying degrees by fish silage and growth experiments are carried out to determine the optimal inclusion level of fish silage. Results of these experiments will be available from the beginning of 2018.

More information: mike.vantland@ilvo.vlaanderen.be, els.vanderperren@ilvo.vlaanderen.be

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