Page 80 - New additives and ingredients in the formulation of aquafeeds

Applicability. Calculation of the increase in cost and return
The amount of product to be included in a commercial feed is limited to a
certain extent by its consideration as an additive, not an ingredient. These
kinds of products (acidifiers, probiotics, enzymes) are commonly included
in very small amounts ranging from 0.5 to 5 g/kg. The amount of enzyme
extract included in a commercial feed to produce a significant improvement
on growth and feed efficiency will depend on its concentration of active
product (UA/g). Considering the relative low concentration of protease
activity in enzyme extracts used in the present study, they were included at
a quite high level (12 g/kg).
The calculations were made considering the following assumptions:
Inclusion of the additives in feeds should not result in a modification in the
cost or main features of the production process.
All calculations will consider only the production of CEE, taking into account
its comparative lower cost and positive biological effect.
The average market price for commercial feeds provided to juvenile fish is
around 1.20 €/kg.
Addition of 12 g CEE per kg of feed (with a cost of 0.85 €/g) should result in
a selling price for weaning feed of 1.20 + 10.20 = 11.40 €/kg.
Such a high value, which represents nearly 10 times current market price
of feeds, points to the unviability of the addition, at least under current
operational costs. Nevertheless, a completefinancial evaluation requires also
making an estimation of the expected return. The following assumptions
were considered to make such estimation:
The information used is based in average data from the more commonly
cultured species in the Mediterranean, the gilthead seabream ( Sparus
aurata).
Three different stages in the production cycle were considered: juveniles
(post-weaning to fingerling; 0.5-15 g), medium grower (15-150 g) and market
size (150-300 g).
FCR in each stage is different; juvenile fish presents better values, although
they get worse with age. In this example, values of 2.0, 2.3 and 2.6 were
considered for each of the three growth stages. Although in the present
work (section 3) the improvement in FCR was only demonstrated in juvenile
fish, it was also applied linearly to older fish for this estimation.
Calculation of the feed consumed in each growth stage, as well as total
consumption, was made using average values of FCR for this species.
The composition and cost of feed used in each growth stage are different.
Although market prices of feeds are continuously changing, in the present
example the values considered were 1.2, 1.0 and 0.85 €/kg.
78 Use of purified extracts from fish viscera as an enzyme additive in feeds for juvenile marine fish