Reproductive Performance of Rainbow Trout (O. mykiss) Broodstocks Fed on Different Feeds

Introduction In recent years, the research of feedstuffs alternative to fish meal, in order to increase the sustainability of the productive cycle, has also been focalized on the feeding of rainbow trout (Oncorhynchus mykiss) broodstocks. The feeding of broodstocks plays a key-role because it affects the quality of the gametes, their fecundity, hatching rate, fry survival and incidence of larval deformation, regardless of genetic selection and the strain employed. Efforts are being concentrated on new diets able to guarantee health benefits, satisfying the essential requirements of females and males, as well as a good quality of gametes, larvae and fingerlings. Based on these assumptions, a trial was carried out employing 4-year-old broodstocks of rainbow trout in order to evaluate the effects of two feeds, containing feedstuffs of different protein and lipid source, on reproductive performance in terms of the quality of eggs, hatching rate and fingerling survival rate. Materials and Methods Four months prior to the spawning season, broodstocks were selected and divided into two experimental Groups, with two replicates each (GF1-GF2, GV1-GV2). Groups GF were fed a diet containing fish meal and fish oil as control feed. Groups GV received a diet including legume protein feedstuffs and oil of vegetable origin (50% linseed oil instead of 50% fish oil). Proximate composition and fatty acid profile of the two feeds were analysed according to international methods. On viable eggs, incubated at 10°C water temperature, the hatching rate and fingerling survival rate at 60 days were recorded in the different Groups. Data were submitted to one-way ANOVA and the differences between the means were evaluated by means of the Student-Newman-Keuls test (SAS, 1989) and considered significant at p<.01. Results and Discussion Gamete and fingerling data were different among the batches, showing a significantly higher performance with regard to the quality of viable eggs in Groups GF compared to Groups GV. The hatching rate of GF was 92 ± 2% versus 71 ± 3% of GV. The survival rate of fingerlings at 60 days also showed notable differences being 74 ± 4% vs 49 ± 3% in GF and GV groups, respectively. Based on the results of this trial, it is possible to assume that feedstuffs containing vegetable protein and fat administered to broodstocks affected the quality of gametes and the progeny of rainbow trout negatively.