Use of Live Baker's Yeast, Saccharomyces cerevisiae, in Practical Diet to Enhance the Growth Performance of Galilee Tilapia, Sarotherodon galilaeus (L.), and Its Resistance to Environmental Copper Toxicity

The potential use of dietary probiotics to enhance the growth and health of aquatic animals has recently attracted intensive attention. Therefore, this study was conducted to evaluate the growth response of Galilee tilapia, Sarotherodon galilaeus (L.), and its resistance to waterborne copper toxicity. Fish (2.5-3.3 g) were fed a diet containing either 0.0 or 10 g live yeast, Saccharomyces cerevisiae, for 6 wk. After the feeding trial, fish at both diets were exposed to 0.0 or 1 ppm Copper (Cu) for 24 h, or 5 ppm Cu for 1 h (T1, T2, or T3 for groups fed basal control diet and T4, T5, or T6 for groups fed yeast supplement). The growth-promoting influences of baker's yeast were observed. Feed utilization was significantly improved, and the biochemical parameters such as serum glucose, lipids, and protein increased when fish were fed a yeast-enriched diet. No significant dietary effects were observed on creatinine, aspartate amninotransferase, and alanine aminotransferase because of yeast supplementation. After Cu exposure, the different biochemical parameters and Cu residues were significantly affected by yeast supplement, Cu levels, postexposure time, and their interactions (P < 0.05). Fish in all treatments biochemically recovered the effect of Cu toxicity within 4-8 days. The comparison of Cu residues in Cu-treated groups, at the same times, revealed that yeast supplementation reduced Cu absorption and accumulation in fish body (P < 0.05). The obtained results indicate that baker's yeast could be used for Galilee tilapia culture to improve its growth performance and its resistance against the waterborne Cu toxicity.