Incubation of rainbow trout egg using green tea extract and copper fiber
2009
Hatakeyama, M., Hokkaido. Fish Hatchery, Eniwa (Japan) | Koide, N.
The prevention of soft egg shell disease by treatment with green tea extract was demonstrated in rainbow trout fertilized eggs. The eggs were dipped in 0.2% green tea extract for 30 min a maximum of six times and the hardness of the egg was evaluated using a fruit penetrometer. At 264 temperature units (degree x days), figures for the average hardness of the eggs treated once, twice, four times, six times and without treatment were l.4, 1.6, 1.7, 1.7 and 0.9 kg, respectively. The eyed rate of the eggs without treatment was relatively low value (67.7%) when compared with those treated with green tea extract (77.8 to 80.2%). The hatching rate of the untreated eggs was 59.3%, while the rates for eggs treated once, twice, four times and six times were 76.8, 79.7, 53.7 and 44.4%, respectively. The cause of the low value observed in the hatching rates of the eggs treated four and six times respectively was considered to be the abnormal hatching due to over treatment. The joint usage of green tea extract to prevent soft egg shell disease and the copper ion used to control the water fungi infection was used to evaluate the effectiveness in rainbow trout fertilized eggs. The eggs were dipped in a green tea extract solution at 0.2 or 0.4% strength for 30 or 60 min. Following the green tea extract treatment, the eggs were incubated under running water containing 8.0 mg/L of copper ion supplemented from the copper fiber until the eyed stage. During the test treatment, the dipping in the solution of green tea extract at 0.4% for 30 min followed by the incubation supplemented with copper ions successfully inhibited the occurrence of soft egg shell disease and the invasion of water fungi.
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