Ralco, a US-based functional ingredient supplier currently partnering with Rangen/Wilbur-Ellis Nutrition, has developed a feed supplement package, ONE CURRENT™, for use in aquaculture feeds. Containing a proprietary blend of MICROFUSED® essential oils, ACTIFIBE® prebiotic, and Yucca schidigera, ONE CURRENT purports to improve gut health and growth performance of intensively cultured finfish and may also have beneficial effects on water quality in such rearing systems. Studies have been conducted to evaluate ONE CURRENT in feeds for various finfish, but the product has not been rigorously evaluated in salmonids. Accordingly, the present work is proposed to evaluate the response of Rainbow Trout to ONE CURRENT-supplemented feed in optimal vs. sub-optimal rearing conditions.
Juvenile Rainbow Trout were fed a commercially manufactured diet with or without supplementation of the functional feed ingredient ONE CURRENT and reared for 8 weeks under optimal environmental conditions (1st use water) followed by an additional 8 weeks of rearing under suboptimal conditions (3rd use water). Dietary supplementation of ONE CURRENT had no adverse effects on growth performance in juvenile Rainbow Trout under both optimal and suboptimal rearing conditions. Both feeds were readily accepted and feeding behavior was aggressive during rearing under optimal conditions. Feeding was expectedly less active during rearing under suboptimal conditions, but fish fed the ONE CURRENT-supplemented feed exhibited a significantly more robust feeding response during this phase. Survival in 1st use water was nearly 100% in both groups, but mortality attributed to reduced environmental quality and gill hyperplasia steadily increased throughout the time fish were in 3rd use water. However, the onset of mortality was delayed, and cumulative mortality was significantly lower among fish fed the ONE CURRENT supplemented feed. Greater feeding response and survival following exposure to 3rd use water suggests that dietary supplementation with ONE CURRENT may increase trout resilience and help to maintain performance under challenging rearing conditions.