Introduction. Organic selenium (OSe) has an advantage in reducing oxidative stress in comparison to inorganic forms and incorporates into skeletal muscles, kidney, liver, and gastrointestinal mucosa proteins as selenomethionine and selenocysteine. It is an essential micronutrient for fish (Martinez-Alvarez et al., 2005). Yeast cell wall has been proven as an immunostimulant and health improver for fish and other animals (Selim & Reda, 2015).
Materials and methods. The effect of three dietary inclusion levels (0, 0.5 and 1.0 kg/ton) of a feed additive, based on OSe and yeast cell wall (AQUASAF®) on tilapia culture performance was evaluated, during 150 days. Three diets with the three inclusion levels were prepared for each culture stage (40% protein for starting; 35% protein for growing; 30% protein for finishing). The experiment was designed with 6 replicates per treatment; each replica had 60 fish (0.5 ± 0.1 g initial weight). Fish were fed 4 times a day, adjusting the feed ration to fish weight (10% at starting and 5% at growing and finalization stages). Trial was conducted in a system with 18 circular tanks (2m diam), with controlled temperature (28ºC ± 0.14). Growth, survival, feeding efficiency, hepatosomatic and viscerosomatic indexes were evaluated.
Results and discussion. Growth results are summarized in Table 1. No differences were detected in survival, feed conversion rate, hepatosomatic and viscerosomatic indexes.
Both ingredients combined have a positive effect in tilapia growth without affecting health and survival. Other reports show similar effect of Se, improving growth, survival, and feed utilization with 0.5 g Se/kg diet (Abdel-Tawwab and Wafeek, 2010).
Conclusion. The feed additive (AQUASAF®) did not compromise health of tilapia. For better performance in terms of growth, it is suggested the inclusion of 0.5 kg AQUASAF®/ton of feed.
Martínez-Alvarez et al., 2005. Rev. Fish Biol. Fish., 15:75-88;
Abdel-Tawwab, M. & Wafeek, M. (2010). Journal of the World Aquaculture Society, 41: 106–114;
Selim, K. M., & Reda, R. M. (2015). North American Journal of Aquaculture, 77(1), 22-30.
Key words. Tilapia, Organic Selenium, Yeast cell wall.
Presented at CLANA 2016.