Long-term dietary diludine (diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridi-nedicarboxylate) intake and gamete storage affect alpha-tocopherol status and reproductive performance in female rainbow trout, Oncorhynchus mykiss

Rainbow trout broodstocks were fed diets with varying levels of diludine [0 (D0; control), 0.25 (D1), 0.5 (D2) and 1 g kg(-1) (D3)] during 2 consecutive reproduction seasons. Fish were started to be fed 3 months before spawning for the first reproduction season and they were kept on the same diets as well as an additional dietary group with 3 g kg(-1) dietary diludine (D4) until the following reproduction season, providing short and long-term dietary treatments. Gametes storage at 6 degrees C for four and fifteen days prior to the fertilization in the first and second reproduction season, respectively, was also tested. Short-term feeding trial did not influence reproductive performance when the eggs were fertilized immediately after stripping, whereas survival at eyed-stage embryos significantly decreased in eggs, from fish fed diludine free diet, fertilized after 4-day storage. Dietary diludine level corresponded with increasing level of vitamin E in the eggs, which positively correlated with survival at eyed-stage embryos from the eggs with or without 15-day storage after long-term feeding. Fish fed the diet with highest level of diludine (D4) produced eggs higher in number but smaller in size in comparison to those from the other four experimental groups. In eggs fertilized after 15-day storage, survival rate was 20-fold higher in D4 diet fed fish in comparison to the other experimental groups. Our overall results indicate that dietary diludine has vitamin E sparing effect in the eggs and protects gamete viability during the storage when it is provided at 3 mg kg(-1) dietary level, which result in lower lipid peroxidation and higher reproductive performance.