In both trials, gonadosomatic indices were not significantly different among dietary groups. Egg size remained unaffected by the levels of vitamin A in the broodstock diets. In both feeding trials, the levels of retinyl palmitate and retinol, the two main storage forms of vitamin A, were significantly higher in oocytes from 1A700 and 2A200 groups compared to other dietary groups; whereas, the level of retinoic acid remained unaffected. In trial 2, broodstock females fed diet 2A200 showed better fecundity than females fed diets 2A0 and 2A20. A significant decline in survival from the eyed stage onwards was noticeable in group 1A700 in trial 1 but no differences were found in trial 2. At the swim-up stage, trout fry from broodstock fed diet 1A20 displayed significantly improved growth rates compared to other dietary groups in trial 1; whereas, in trial 2, trout fry from 2A200 group exhibited the best growth performance. The expression of genes coding for retinoid receptors and other associated nuclear receptors was not significantly different among dietary groups at any developmental stage considered and no skeletal malformation was recorded in offspring.
The results indicate that feeding rainbow trout broodstock a high level of vitamin A induced mortality at embryonic stages but was not teratogenic as no skeletal malformation was recorded at late developmental stages. However, quite high levels of vitamin A (60–200 IU/g) were necessary to sustain fecundity of broodstock and early growth of offspring.