Collection of feed spill and faeces from tank outlet. The FOGAS project

Sammendrag

Feed spill collection and stripping of faeces are common tasks in fish nutritional trials at Nofima’s
Research Station for Sustainable Aquaculture at Sunndalsøra. The established method for collection of
feed spill requires manual work and is time consuming. A simpler method for feed spill collection, which
also allowed collection of faeces at the tank outlet, was developed. The result was a demonstrator
denoted ‘Spillbox’.
The Spillbox, with a vertical screen with horizontal wires, was placed at the tank outlet. Uneaten feed
was collected in a container separated from the water flow. By using compressed air, faeces were
collected in another container, also kept away from the outlet water. In the recovery test (n=4) with one
feed, 87 % of the feed was collected.
Feeding salmon (biomass 46 kg) one diet containing Y2O3, faeces was collected for 24 hours, resulting
in 31 g of faeces (mean, n=3). Apparent digestibility measured from faeces collected with the Spillbox
resulted in very small variation among replicates, and digestibility of dry matter and energy was very
similar to data obtained by stripping. The calculated digestibility of fat and nitrogen (protein) deviated
from data obtained with stripping.
The Spillbox worked satisfactory for its purpose with the feed type used. For further documentation of
the Spillbox for feed collection, testing with several pellet sizes and physical pellet qualities is required.
For collection of faeces, it is recommended to investigate the deviation in AD values obtained with the
Spillbox method and the stripping method.
Faeces quality varies with feed, and these initial tests indicated that the system may be controlled and
adjusted for varying faeces qualities. However, a certain firmness of the faecal particles is required for
collection with the Spillbox.
It is relevant to upscale and adapt the Spillbox for collection and reuse of uneaten feed, and collection
of faecal matter (sludge) in commercial land-based salmon farming. Theoretic mass balance and
amount of sludge produced in commercial farming in different situations was calculated.
In conclusion, the Spillbox could be used for collection of uneaten feed and for collection of faeces for
digestibility measurements for the feed tested. Some optimization and adjustment of the system when
used under different conditions, and documentation of its accuracy using several feed types is
recommended.

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NVA : hdl.handle.net/11250/3105325