Nutritional investigations
on intensively reared Dentex (Dentex dentex, L.) larvae and juveniles
Aquaflow Technical Leaflet 2002-54
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/
Dentex (Dentex dentex, L) is an attractive candidate
species for Mediterranean aquaculture. This three- year project financed by
the Italian Ministry of Agriculture Politics, under the IV framework of the
law 41/82, studied nutritional aspects of the larval and juvenile stages.
The work focussed on the main nutritionally-related
changes in the biochemical composition throughout early larval rearing; the
data from growth and feed intake responses of juveniles to artificial dry
diets compared to other species under the same conditions and finally
estimates of suitable dietary levels of energy, protein and essential amino
acids to be used in practical feeding of dentex.
Dentex eggs, larvae and juveniles were obtained from
wild spawners. Larval rearing used enriched rotifers and Artemia salina as
live foods. The growth and feeding experiments with dentex fry and juveniles
were carried according to standard protocols under strictly contro1led
environmental conditions. Seven dry pelleted diets providing different
1evels of protein (44-60% DM), lipid (12-17-5% DM) and digestible energy
(18-21kj/gDM) were used to estimate optimal dietary 1evels of macronutrients
for juvenile dentex.
The changes in pattern of the major biochemical
components during early 1arval rearing of dentex were similar to those
outlined for other sparid species investigated to date. The n-3 PUFA and
arachidonic acid were shown to be essential fatty acids (EFA) in this
species. The essential amino acid profile (EAA) of enriched live food did
not show major imbalances when compared to that of dentex larvae. In
contrast, the amounts of EFAs and namely of DHA supplied by the 1ive food
appeared somewhat limiting relative to the dietary needs exhibited by dentex
larvae. A critical EFA status was evoked as a possible cause of the poor
survival observed throughout the larval phase (i-e. 11% at 30 days post
hatch).
The post-weaning performance of 83 fish groups kept at
different temperatures, were used to calculate simple models to predict
growth rates and feed intake of intensively-reared juveniles. These trials
showed the high post-weaning growth potential of dentex with the best
performance being obtained at 25°C. When compared to gilthead sea bream and
sea bass of similar size under the same feeding and farming conditions,
dentex showed superior feed efficiency and nitrogen retention. However,
contrary to the favourable growth, juvenile dentex suffered high mortality
due to their aggressive behaviour. Based on the results of the feeding
experiments, the dietary protein levels for optimal growth performance of
fingerling and juvenile dentex should not be 1ower than 45 and 50% DM
respectively in feeds supplying not less than 18.5kj/gDM of digestible
energy. This corresponds to digestible protein/energy ratios of 23 and 25
g/Mj. Dietary carbohydrates were poor1y utilised as energy by this strictly
carnivorous species. On the other hand, increasing the lipid content of the
diet up to 17.5% DM, led to a significant protein sparing effect. This
suggests the use of medium-high lipid levels in practical feeds for dentex.
The essential amino acid requirements of juvenile
dentex are similar to those a1ready reported for other carnivorous bony fish
studied to date. They could be easily met if substantial amounts of high
quality fishmeal are used in practical diet formulation.
* research granted by the Italian Ministry for
Agriculture and Forestry Politics, General Directory for Fishery and
Aquaculture, within the IV framework of the law n°41/1982
For information:
Prof. Emilio Tibaldi
Dipartimento di Scienze della Produzione AnimaleUniversità di Udine
Udine
Italy
Phone : +39 0432 650110
Fax : +39 0432 660614
E-mail : tibaldi@hydrus.cc.uniud.it