One of the most important challenges in the aquaculture industry is the optimal management of nutrition and maintaining the health of farmed fish under stressful environmental conditions such as high stocking density, poor water quality, transportation, and changes in water salinity. These factors can weaken the immune system, increase the susceptibility of fish to diseases, and reduce breeding performance (Sado et al., 2008). To address these challenges, the use of dietary additives, including probiotic supplements, has been suggested as an effective strategy to increase survival rates and improve the general health of fish (Imanpour and Roohi, 2015). Saccharomyces cerevisiae is a unicellular yeast from the fungi phylum that has diverse and beneficial functions in the host body due to its content of important biological compounds such as B vitamins, nucleotides, glutamate, inositol, and -β-glucan. This yeast can act as a dietary supplement, appetite stimulant, toxin and heavy metal adsorbent, and immune system enhancer (Hosseinifar et al., 2012; Siwicki et al., 1994). Given the biological and nutritional properties of Saccharomyces cerevisiae, the present study was designed to determine the effect of Vivacell (Saccharomyces cerevisiae) probiotic supplement on blood indices, survival, and salt tolerance in rainbow trout fry. This study was conducted in line with the use of safe and natural additives in aquatic animal diets to increase the health and sustainability of farming systems and can be an effective step towards improving production performance and managing environmental stresses in the aquaculture industry.
Material and Methods: For this study, 132 rainbow trout fry with an average initial weight of 20 ± 1.87 g were obtained from a private breeding center. The fish were randomly introduced into 12 aquariums (each aquarium containing 11 fish) and were placed under different nutritional conditions with different levels of Vivacell (Saccharomyces cerevisiae) for 8 weeks of the experiment. The experiment was randomly performed in four different nutritional treatments with different probiotic amounts (0, 0.1, 0.5 and 1% per kg of food) and in three replications. At the end of the experiment, the survival rate of the fish was determined by counting the number of surviving fish in each treatment. To examine changes in blood indices, three fish were randomly selected from each treatment and anesthetized with clove essential oil. Blood was collected from the caudal vein using heparin-containing syringes and transported to the laboratory. Hematological parameters were measured. (Goldenfarb et al., 1971; Larsen, 1964). After the end of the feeding period, in order to evaluate the resistance of fish to salinity stress, fish were exposed to 12 g/L salinity for one week and the survival rate was determined in one week. The obtained data were analyzed using SPSS version 16 statistical software. To examine the difference between treatments, a completely randomized design and one-way and multiple range Duncan variance tests were used at a significant level (p<0.05). (Nochalabadi et al., 2023; Sathasivam et al., 2019).
Result and Discusion: The study of blood indices at the end of the rearing period showed that the use of Saccharomyces cerevisiae probiotic in the diet of rainbow trout fry significantly improved some of them. The results of the study of salinity resistance in rainbow trout fry fed with different levels of Saccharomyces cerevisiae probiotic showed that when exposed to salinity stress of 12 g/l for 7 days, there was no significant difference in the percentage of survival between the control group and the experimental treatments (p<0.05). All groups showed 100% survival during the 7-day period. This finding indicates that the stress applied at this level of salinity was not sufficient to create a significant difference in the resistance of the fish, especially in the presence or absence of the probiotic. However, in contrast to the results of the present study, the results of the study by Ramzannejad et al. (2021) showed that Bioaqua supplementation significantly increased the survival of carp. In the present study, the number of red blood cells and white blood cells in the 0.5 and 1 treatments significantly increased compared to the 0.1 treatment and the control group. However, the results of the present study are consistent with the results of Akbari Nargesi et al. (2019), Ramzannejad et al. (2021), and Asadi et al. (2023).
Conclution: Overall, the results showed that the probiotic Saccharomyces cerevisiae could be effective in some indicators such as blood indices and salt tolerance, although its effects on survival rate and other physiological indicators examined in this study were not significant. Therefore, the use of this probiotic in culture conditions can be used as an auxiliary tool to improve some fish health parameters, but further research is needed to more fully evaluate its effects in different culture conditions. |
