Effects of Dietary Moisture Content on the Growth and Gastrointestinal Evacuation of Sub-adult Olive Flounder Paralichthys olivaceus in the Summer and Winter Seasons

Abstract

Two experiments were conducted to investigate the effects of dietary moisture content on the growth and gastrointestinal evacuation of sub-adult olive flounder (Paralichthys olivaceus) in the summer and winter seasons. In the first experiment, three experimental diets containing different moisture levels (7%, 15%) and additives were prepared by adding water and commercial additives (1% nutrients, 1% digestives) to commercial extruded pellets. Fish (initial weight: 332 ± 9.2 g) were distributed randomly into six 3000 L tanks (25 fish/tank) in a flow-through tank system. Two replicate groups of fish were fed the experimental diets to satiation for 14 weeks during the summer season (21.4 ± 2.5 ℃ ). Survival, weight gain, feed efficiency, and daily feed intake did not differ significantly among groups. In the second experiment, two experimental diets containing different moisture levels (8%, 23%) were prepared by adding water to commercial extruded pellets. Fish (initial weight: 646 ± 6.7 g) were randomly distributed into six 3000 L tanks (20 fish/tank) in a flow-through tank system. Three replicate groups of fish were fed the experimental diets to satiation for 19 weeks during the winter season (12.2 ± 1.2 ℃ ). Weight gain, feed efficiency, and daily feed intake did not differ significantly among groups. Gastrointestinal evacuation rates were determined after the end of the winter feeding trials. The stomach contents of fish fed diets containing different moisture levels peaked within 3 h after feeding and then decreased gradually over 40 h to approach pre-feeding levels.Intestinal contents began to accumulate 3 h after feeding and reached a maximum at 32 h, then declined until nearly complete evacuation around 56 h. The stomach contents reached moisture levels of approximately 70% within 3 h after feeding and then increased gradually. No considerable difference in moisture levels was observed in the stomach contents of fish fed diets with different moisture contents. The results of this study suggest that the gastric evacuation of sub-adult olive flounder was not affected by dietary moisture level and the addition of water to the diet had no beneficial effect on the growth of sub-adult olive flounder in the summer and winter seasons.

Effects of the Dietary Moisture Levels and Feeding Rate on the Growth and Gastric Evacuation of Young Olive Flounder Paralichthys olivaceus

“…In this study, an increase in dietary moisture from 9% to 40% displayed no beneficial effects on the growth and feed utilization of olive flounder (106 g average initial weight). Similar nonsignificant differrences for the weight gain and feed efficiency were observed in the subadult flounder (332 g) fed diets containing 7-15% moisture under the rearing water temperature of 21°C, as well as in 646-g flounder fed between 8% and 23% moisture diets at the suboptimal water temperature of 12°C (Kim et al, 2011). Lee et al (2000b) reported that dietary moisture content displayed no significant effects on the weight gain or feed efficiency of Korean rockfish Sebastes schlegeli, but Chatzifotis et al (2005) reported that dentex Dentex dentex grew more effectively when receiving diets containing 20% moisture compared to 7% or 40% moisture levels.…”

“…In this study, at 30 h postfeeding, the intestine of the flounder was primarily evacuated. However, subadult flounder (848 g) fed diets containing 8% and 23% moisture under a rearing water of 12°C required 56 h to evacuate their intestines in previous studies (Kim et al, 2011). The variations in gastric evacuation time may be due to differences in the fish size, the dietary composition, or the water temperature employed during these studies.…”