Effect of protein source on the reproductive performance of female rainbow trout, Oncorhynchus mykiss (Walbaum)

Two-year-old rainbow trout, Oncorhynchus mykiss (Walbaum), females were fed three different diets containing animal protein R1 or vegetable protein R2 and R3 over 12 months from March 1993 until February 1994. Diets containing vegetable protein slightly depressed broodstock growth rates, although the final weight differences among groups were not statistically significant. The mean total fecundity (eggs female−1) was significantly higher (P<0.05) in group R1. With regard egg composition, amino acids levels in group R3 were significantly lower (P<0.05) than in the other groups. Although the total amino acids of eggs from the R1 and R2 groups presented a similar pattern, the essential amino acids lysine, threonine, cystine and isoleucine were lower in the R2 group. The ω 6 and ω3 fatty acid levels of the eggs were also affected by the protein source of the diet. In both the R2 and R3 groups, the plasma levels of 17β-estradiol reached a maximum level one month later than the R1 group. For the R2 and R3 groups, plasma levels of vitellogenin peaked after a one-month delay; peak values were significantly lower (P< 0.05) than in the R1 group. Similarly, the vitellogenin content of the eggs was in accordance with plasma levels in broodstock females. The results of the present study demonstrated that the composition of diet significantly affected reproductive indices and composition of the eggs.