Effects of digestible
protein and lipid levels in practical diets on growth, protein utilization
and body composition of juvenile rockfish (Sebastes schlegeli)
Sang-Min
Lee, Im Gi Jeon, Jong Yun Lee-2002
Aquaculture, 211(1-4): 227-239
Abstract:
A feeding trial of three dietary digestible protein
(DP) levels (37%, 42% and 47%) and two dietary digestible lipid (DL) levels
(7% and 14%) factorial design with three replications was conducted to
investigate the proper dietary protein and lipid (energy) levels for the
growth of juvenile rockfish. Fish, average initial weight 21.9 g, were fed
the experimental diets for 20 weeks. Weight gain improved with increasing
dietary DP and DL levels. Weight gain of fish fed the diet containing 47% DP
was significantly higher (P<0.05) than that of fish fed the diet
containing 37% DP, and was not different from that of fish fed the diet
containing 42% DP at the 14% DL level. However, weight gain was not
significantly affected by dietary DP level at the 7% DL level. Feed
efficiency ratio of fish was improved as dietary DP and DL levels increased,
whereas there was no significant difference between those of fish fed the
diets containing 42% or 47% DP at the same dietary DL level. Feed efficiency
ratio of fish fed the 14% DL diets was significantly higher (P<0.05)
than that of fish fed the 7% DL diets at the same DP level. Hepatosomatic
index (HSI), visceralsomatic index (VSI), protein efficiency ratio, and
protein retention were significantly influenced by dietary DL level, but not
by dietary DP level. Daily feed intake tended to decrease with increasing DP
and DL levels. Lipid contents of whole body, liver and viscera increased
with increasing DP and DL levels, whereas dorsal muscle lipid was not
affected by dietary DP and DL levels. The apparent digestibility
coefficients (ADC) of protein and nitrogen-free extract (NFE) were not
significantly affected by dietary DP and DL, while ADC of dry matter, lipid
and energy increased with dietary DP and DL. The results of this study
indicate that an increase of dietary lipid level has protein-sparing effect,
and the diet containing 42% DP and 14% DL (4.2 kcal DE/g diet) is optimal
for growth and effective protein utilization of juvenile rockfish.
(Faculty of Marine Bioscience and Technology,
Kangnung National University, Kangnung 210-702, South Korea, Tel.:
+82-33-640-2414; fax: +82-33-640-2410, e-mail: smlee@knusun.kangnung.ac.kr)