We evaluated the effects of rice distillers dried grain (DDG) as a partial replacement for fish meal in the practical diet on growth performance, feed utilization, and body composition of juvenile olive flounder Paralichthys olivaceus. Six isonitrogenous and isocaloric diets were formulated to contain 0%, 7%, 14%, 21%, 28%, and 35% DDG (designated DDG0, DDG7, DDG14, DDG21, DDG28, and DDG35, respectively). Three replicate groups of juvenile olive flounder averaging 9.6 ± 0.2 g were fed one of the experimental diets to visual satiety twice daily for 8 weeks. Neither survival nor daily feed intake was affected by the dietary DDG levels. Weight gain of the flounder fed the DDG28 and DDG35 diets was lower than that of flounder fed the DDG7 diet. The feed efficiency of flounder fed the DDG28 diet was lower than that of flounder fed the DDG0, DDG7, and DDG14 diets. The protein efficiency ratio of flounder fed the DDG28 diet was lower than that of flounder fed the DDG7 diet. The proximate composition of muscle was not affected by the dietary DDG levels. The plasma contents of total protein, glucose, cholesterol, glutamate oxaloacetate transaminase, phospholipid, and triglyceride were not affected by the dietary DDG levels. The results of this experiment suggest that DDG has the potential to replace fish meal and could be used up to 21% DDG without any negative effects on the growth and feed utilization of juvenile flounder.

This study compared the effects of diets consisting of experimental extruded pellets (EP), commercial soft extruded pellets (SEP), and raw-fish-based moist pellets (MP) on the growth, flesh quality, and histology of the Korean rockfish Sebastes schlegeli. Three replicated groups of 60 fish each (initial mean weight 152 g) were fed one of two experimental EPs (EP1 and EP2), two commercial SEPs (SEP1 and SEP2), or MP for 11 weeks. The survival, weight gain, and final mean weight of the fish did not differ significantly among the groups. The highest feed efficiency was in fish fed MP (P<0.05), and the protein efficiency ratio of fish fed MP was significantly higher than that of fish fed EP1, EP2, or SEP1, but not significantly different from that of fish fed EP2. The daily feed intake of the fish fed the EPs and SEPs was significantly higher than that of the fish fed MP (P<0.05). The condition factor, Hepatosomatic Index, and Viscerasomatic Index of the fish did not differ significantly among the groups. No notable differences in the textural properties of the dorsal muscle, plasma biochemical parameters, or histological features of the fish were observed in fish fed any diet. This suggests that extruded pellets can be used to feed growing Korean rockfish without compromising growth, flesh quality, or histopathological change in comparison to raw fish-based moist pellets.

Effects of Dietary Inclusion of Distillers Dried Grain as a Partial Replacement for Fish Meal on Growth Performance of Juvenile Rockfish Sebastes schlegeliKi-Min BAE Sang-Min LEE ㆍ (Gangneung-Wonju National University) AbstractA feeding experiment was conducted to determine the use of distillers dried grain (DDG) as a partial replacement for fish meal in the diet for juvenile rockfish, Sebastes schlegeli. Four iso-nitrogenous (50% crude protein) and iso-caloric (4.3 kcal/g) diets (designated as DDG0, DDG7, DDG14, and DDG21) were formulated to contain 0, 7, 14, and 21% DDG. Triplicate groups of juvenile rockfish (initial body weight, 10.2±0.2 g) were fed one of the experimental diets to visual satiety twice a day (09:00 and 17:00) for 8 weeks. At the end of the feeding trial, survival of rockfish was above 97% and not affected by dietary DDG levels (P>0.05). Weight gain, feed efficiency and daily feed intake of juvenile rockfish were significantly decreased with increase of dietary DDG levels (P<0.05). Condition factor, hepatosomatic index and visceralsomatic index of juvenile rockfish were not significantly affected by dietary DDG levels (P>0.05). No significant differences were observed in the contents of moisture, crude protein, crude lipid and ash of the whole body and dorsal muscle in juvenile rockfish fed the experimental diets (P>0.05). Therefore dietary inclusion of DDG as a replacement for fish meal could depress the growth of juvenile rockfish.

The aim of this study was to investigate the effect of diet extruder conditions, such as feed-loading rate and screw speed, on growth performance and biochemical responses in olive flounder Paralichthys olivaceus. Over 8 wks, we used four identical diets (triplicated per treatment) with differing ratios of feed-loading rate (kg/h):screw speed (rpm/ min) in a laboratory-scaled twin-screw extruder of 50:640, 80:640, 120:640, and 80:400, designated as EP1, EP2, EP3, and EP4, respectively. Screw speed impacted the buoyancy of experimental diets. Diets produced at a screw speed of 640 rpm/min floated for > 24 hrs, whereas those produced at a speed of 400 rpm/min sank between 10 s and 5 min. Fish that were fed EP1 and EP4 diets grew significantly faster than those fed EP2 and EP3 diets. Fish fed EP1 diets ate and gained weight most efficiently among treatments, a result that is likely to be related to feed-loading rate, i.e., ingredients extruded at a low feed-loading rate may have more time to cook in the pre-conditioner of the extruder. A cooked diet may be easier to digest in fish. Fish fed EP4 diets also showed significant weight gain, as compared to those fed EP2 and EP3 diets. However, we found no differences among treatments in proximate compositions of dorsal muscle, liver, and viscera of fish. Our results suggest that extruder conditions, may influence feed quality, impacting feed efficiency and growth of fish.