Effects of the dietary
protein/lipid ratio on growth and nutrient utilization in common dentex (Dentex
dentex L.) at different growth stages
A. Skalli, M.C. Hidalgo, E. Abellán, M. Arizcun, G.
Cardenete-2004
Aquaculture, 235(1-4): 1-11
Abstract:
Dentex is considered suitable for aquaculture due to
its ready adaptation to culture systems, acceptance of formulated feeds and
rapid growth rates. However, little information on the nutritional
requirements or growth rates under controlled conditions has been reported
for this fish. Thus, two feeding trials were performed, at different growth
stages, to identify suitable protein and lipid (energy) levels to be used in
formulating dry diets for this species. As the first step, a 3×2 factorial
experiment was conducted to determine the optimum protein-to-energy (P/E)
ratio for fingerling dentex. Triplicate groups were fed to satiation one of
six practical diets with increasing levels of protein (50%, 53% and 57% DM)
and two energy levels (20 and 22 kJ g−1) within each
protein level. Protein utilization was enhanced by a sparing effect of
dietary lipid at 19.7%. These data suggest that, when the energy level of
the diet is maintained at 22 kJ g−1, the dietary protein
level for fingerling dentex can be lowered from 57% to 50%. In the second
experiment, with larger fish, triplicate groups of fish were fed one of six
diets with two energy levels (20 and 22 kJ g−1) and three
P/E ratios (19, 21 and 23 g MJ−1). Thus, the dietary
protein level tested ranged from 38.7% to 51.14% DM. The results in the
second trial suggest that, when protein efficiency or retention are
considered, even dietary levels of 43.4% CP and 19 g protein MJ−1
of P/E, and a calculated available energy level (22 kJ g−1)
could be assumed to be adequate levels for formulating practical diets for
this species at this growth stage. It can be concluded that, for the two
size classes of dentex used, dietary lipid had a protein-sparing effect.
(Dpt. Biología Animal y Ecología, Facultad de
Ciencias, Campus Fuentenueva, Universidad de Granada, 18071, Granada, Spain,
e-mail of M.C. Hidalgo: chidalgo@ugr.es)