Page 73 - New additives and ingredients in the formulation of aquafeeds

In this first experiment, the addition of the PEE did not result in a
significantly positive effect on growth or feed efficiency of the fish. In a
second experiment the products were obtained from black scabbardfish
(Aphanopus carbo) and Argentine shortfin squid (Illex argentinus) and some
of experimental parameters were modified. The products were included at
a higher level (12 g/kg) and two different types of products were evaluated;
the PEE obtained after concentration with ammonium sulphate and the
crude extract obtained prior to this step (CEE). The initial evaluation showed
a much higher activity in the products obtained from black scabbardfish
than from Argentine shortfin squid, as well as the presence of activity at
both acid (6,5) and alkaline (8,0) pH (Table 3).
Table 3. Protease activity (U/g) measured in the extracts prepared from viscera
of Aphanopus carbo and Illex argentinus at two different pH
pH 6.5 pH 8.0
CEE Aphanopus 1,318 3,194
PEE Aphanopus 2,000 3,146
CEE Illex 539 265
PEE Illex 201 424
The evaluation of the protease activity present in the feeds after inclusion
of the different products showed is detailed in Table 4. Results evidenced
a basal protease activity at both pH in the control feed, probably due to the
residual activity in some of the ingredients used (e.g. fish meal) and also
the significant increase of such activity after addition of the products. The
higher increase at acid pH was obtained when using the products obtained
from squid, while the higher activity at alkaline pH was measured when
using those from scabbard fish.
Table 4. Protease activity at pH 8.0 measured in the experimental feeds. The
differences in relation to the control feed are shown as percentage increase
Feed Protease activity
(U/g feed)
% increase
over control
Protease activity
(U/g feed)
% increase
over control
Control 4.0 - 8.0 -
CEE Aphanopus 3.7 0.0 11.1 39.1
PEE Aphanopus 4.8 22.0 10.7 34.2
CEE Illex 5.8 45.8 9.0 12.8
PEE Illex 5.6 41.2 8.6 7.2
The experimental design and conditions were similar to those used in the
previous experiment (Table 2). No direct correlation between the total
enzyme activity in the feeds and the final growth or feed efficiency was
observed, but after 40 days, fish fed on the feed including the CEE of black
Use of purified extracts from fish viscera as an enzyme additive in feeds for juvenile marine fish 71