Introduction
Micro algae has been used as dietary supplements to improve growth, health, lipid metabolism and nutritional performance of a range of farmed fish species (Mustafa and Nakagawa, 1995; Güroy et al., 2011; Güroy et al., 2012). Spirulina is one of the most commonly used micro algae in aquafeeds; it is a rich source of protein, vitamins, essential amino acids, minerals, essential fatty acids and antioxidant pigments such as carotenoids (Nakagawa and Montgomery, 2007).
Rainbow trout, Oncorhynchus mykiss is a high commercial value species which have become greatly economically important in Europe where production totaled about 280 000 tones in 2013 (FAO, 2015). Fish farmer and relating sector' producers are searching for suitable dietary additive and/or ingredient in aquafeed. Therefore, the aim of the present study was to determine the effect of dietary Spirulina levels on growth performance of rainbow trout.
Materials and Methods
Juvenile rainbow trout were transported from a local fish farm (Keskinler Trout Farm, Bayramic, Canakkale, Turkey) and acclimated to laboratory conditions at the Fish Nutrition and Aquarium Unit of Canakkale Onsekiz Mart University, Faculty of Fisheries for 4 weeks whilst fed a commercial diet (Bagci Feed Company, crude protein: 50%, crude lipid: 18%). Three hundred fish (∼7 g) were randomly allocated into 150 l circular tanks (20 fish per tank) within a recirculation freshwater system. Fish were fed experimental diets to satiation three times a day for 12 weeks. Each treatment was conducted in triplicate. During the experimental period temperature was maintained at 16 ± 1.5 °C and dissolved oxygen levels at >80% saturation. Water flow rate was approximately 12 l/min per tank.
A basal feed was prepared using fish meal, soybean meal, wheat meal, fish oil and soybean oil. In addition to the control diet (C), two test diets containing 5 (S5) or 10% (S10) Spirulina (S) were added.
Data were subjected to a one-way analysis of variance (anova) and Tukey's HSD multiple range test using Statgraphics 7.0 version for Windows (Manugistics Incorporated, Rockville, MD, USA). The results were treated statistically significant at the p < 0.05 level.
Results
All the experimental diets were well accepted by fish. Growth performance of S5 and S10 groups were higher than the control group (p <0.05). In the fish fed with control diet was obtained lower feed conversion ratio (1.01) compare to fed 5% and 10% Spirulina meal (respectively 0.91 and 0.97). The best protein efficiency ratio (PER) were determined the S5 group (2.45) and the poorest PER in the control group (2.21).
Discussion
According to feeding trial results, it was found that dietary level of 5 - 10% of Spirulina positively influenced growth performance and feed conversion ratio of juvenile rainbow trout.
References
FAO, 2015. Global Aquaculture Production 1950-2013. http://www.fao.org/fishery/statistics/global-aquaculture-production/query/en
Güroy D., Güroy B., Merrifield D.L., Ergün S., Tekinay A.A., Yiğit M. 2011: Effect of dietary Ulva and Spirulina on weight loss and body composition of rainbow trout, Oncorhynchus mykiss (Walbaum), during a starvation period. Journal of Animal Physiology and Animal Nutrition, 95(3): 320-327
Güroy B., Şahin İ., Mantoğlu S., Kayalı S. 2012. Spirulina as a natural carotenoid source on growth, pigmentation and reproductive performance of yellow tail cichlid Pseudotropheus acei. Aquaculture International, 20:869-87
Mustafa M.G., Nakagawa H., 1995. A review dietary benefits of algae as an additive in fish feed. The Israeli Journal of Aquaculture - Bamidgeh 47:155-162
Nakagawa H., Montgomery W.L., 2007. Algae In Dietary Supplements for the Health and Quality of Cultured Fish (Nakagawa, H.; Sato, M. and GatlinIII, D.M. eds.) pp. 133-167. Cabi International, Cambridge, USA.