抄録
This study was conducted to determine the energy and protein requirements of yellowtail to optimize feeding levels during the winter season when they have comparatively low feeding activity. Two feeding experiments were conducted during the winters of two subsequent years in net cages located in different environmental conditions at Mie and Nagasaki prefectures, Japan. At both the locations, commercial soft-dry pellets (SDP) with known digestible energy (DE) and protein (DP) values were fed to 4 groups of fish at satiation levels for 5, 3, 2, and 1 time (s) per week.
In the first experiment, feeding either 2 or 3 times per week produced the best growth offish in Mie prefecture while in Nagasaki prefecture these rations gave the most efficient whole body energy and protein retention. The daily feeding rates (DFR) for the respective feeding frequencies were 2.5-3.7% and 1.3-1.6% in Mie and Nagasaki prefectures. Based on this data, the daily DE and DP requirements per kg body weight for a maximum growth were 43.1-45.1 kcal (180-187kJ) and 4.0-4.2g in Mie and for maintenance of body energy and nitrogen balance 18.5-23.0 kcal (77-96kJ) and 1.7-2.1g in Nagasaki.
In the second experiment, in both the prefectures the fish fed 3 times per week showed higher growth and feed gain ratios, closely followed by the fish fed 2 times. DFR for these feeding frequencies were almost similar to those obtained in Expt. -I; 2.0% for Mie and 1.2% for Nagasaki fish. The daily DE and DP requirements per kg body weight for a maximum growth were 36.1 kcal (151kJ) and 3.6g in Mie and 21.0 kcal (88kJ) and 2.1g in Nagasaki.
The differences between the two locations were postulated to be due to the disparity in feed intake which was governed by water temperature.
