اثرات سلنیوم های مخمری (سلمکس، سلنوسورس و سلپلکس) بر زنده مانی، ترکیب لاشه و مقاومت به استرس در کپور معمولی (Cyprinus carpio)

Introduction: Selenium (Se) has recently received considerable attention in aquatic nutrition. Farmed fish are exposed to various stressors, making nutritional supplements crucial management tools for enhancing stress resistance and optimizing overall health parameters. To reduce the overuse of antibiotics, researches have focused on dietary additives such as selenium to enhance fish health. The incorporation of prebiotics into aquatic diets is an emerging strategy for diseases prevention and enhanced production. Selenium-rich prebiotic yeast combines the benefits of both prebiotic and organic selenium, potentially exerting dual effects. The present study is the first to compare the effects of three selenium yeast types, Selemax, Selensource and Sel-Plex, on growth performance, carcass composition and stress resistance in common carp.
Materials and Methods: In this study, the effects of seven diets containing 0.3 mg Se from Selemax, 1 mg Se from Selemax, 0.3 mg Se from Selenosource, 1 mg Se from Selenosource, 0.3 mg Se from Sel-Plex, 1 mg Se from Sel-Plex per kg of diet, and a control diet without Se supplementation were investigated in common carp (Cyprinus carpio). Each dietary treatment was studied in 2 tanks (replicates) and each tank contained 31 fish with an initial weight of 1.61 ± 0.32 g (mean ± SD) in a completely randomized design.
Results: No significant differences were observed in fish weight, standard length, and condition factor (P>0.05). Selenium yeast supplementation did not significantly affect survival rate during the rearing period and carcass dry matter, crude protein and crude fat (P>0.05). However, feeding with 0.3 mg of Se in the form of Selenosource significantly reduced the carcass ash percentage (P<0.01). After exposure to high-intensity salinity stress (without aeration), no significant differences in survival time were observed (P>0.05).  In contrast, under low-intensity salinity stress (with aeration) survival time increased significantly in fish fed with 0.3 mg Se in the form of Selemax or Sel-Plex (P<0.05).
Discussion: The insignificant difference in the survival rate of the fish indicated suitable rearing conditions. The effect of selenium yeast on the fish growth in different studies is somewhat contradictory and depends on the composition of the feed, experimental conditions, form and concentration of selenium and the health, species and life stage of the fish. While higher levels of selenium yeast will lead to significant differences in the growth of common carp but based on the new standard, selenium consumption is limited and high selenium concentration in the feed causes its accumulation in the environment and environmental problems. Selenium influences lipid, carbohydrate and amino acid metabolism in aquatic animals, but many studies have shown that selenium supplementation has no effect on the proximate analysis of fish. However, in some studies the effect of selenium on the amounts of protein and ash in the carcass has been proven. It seems that the difference in the formula of the diets is an important factor in observing different results even in the same species, since selenium is absorbed more effectively in the presence of other compounds such as vitamins E, D and A. In addition, proteins and fats also affect the bioavailability of selenium. Numerous studies in fish have shown that dietary selenium supplementation can mitigate oxidative stress caused by stressful conditions, however, the type of stressor influences outcomes even within the same species. Despite the beneficial effects of dietary selenium on fish, it has been reported that high dietary intake can lead to a decrease in antioxidant capacity, and this may be why in the present study, fish receiving 0.3 mg Se in the form of Selemax or Sel-Plex performed better than fish fed 1 mg of these types of selenium. Overall, the mechanism by which high selenium intake impairs the antioxidant system in aquatic animals remains unclear.
Conclusion: This study highlights the importance of dietary selenium supplementation for fish health and welfare. Although fish fed the unsupplemented control diet exhibited good growth and a high survival rate compared to the other fish, the basal selenium level was insufficient confer protection against stress. Dietary selenium supplementation enhanced stress resistance. Overall, the use of Selenosource selenium yeast in the diet of common carp was not beneficial but the application of selenium yeast with the brands Selemax or Sel-Plex at a level of 0.3 mg per kg of diet is recommended to increase resistance against stress.