Possibilities of Utilizing Dietary Supplements in Semi-intensive Culture of Deccan Mahseer, Tor khudree (Sykes)

Effectiveness of dietary supplements on the growth performance, survival, nutritional efficiency, body indices and biochemical composition of deccan mahseer (Tor khudree) was evaluated in a semi-intensive culture system. The ponds were fertilized with raw cow dung and single super phosphate. Fish (1.10+0.03 g) at a stocking density of three per square meter were fed for a period of 180 days with the formulated practical diets. The test diet D1 was un-supplemented basal diet, which served as the control while in four of the test diets, D2, D3, D4 and D5, dietary supplements viz. cholicalciferol (1800 IU•kg^-1), soylecithin (3.5%), thyroxine (0.05ppm) and betaine (0.5%), respectively, were added. The inclusion level of the dietary supplement was based on the best results obtained, in terms of growth performance, feed utilization and survival, in previous investigations carried out for the same fish species under laboratory conditions. Feeding soylecithin supplemented diet (D3) resulted in significantly (P 0.05) higher percentage weight gain and specific growth rate (SGR) than was observed with other diets. Survival was independent of the treatments. Feed conversion ratio (FCR), feed conversion efficiency (FCE) and protein efficiency ratio (PER) were significantly better (P 0.05) in the fish fed with the diet D3 compared to fish fed with all other diets. The crude protein efficiency (CPE), crude fat efficiency (CFE) and gross energy efficiency (GEE) in relation to all the treatments were significantly higher (P 0.05) in D3. Among the body indices, viscero-somatic index (VSI) was significantly (P 0.05) higher in D3, cranio-somatic index (CSI) was significantly higher (P 0.05) in the control diet (D1), while hepato-somatic index (HSI) and reno-somatic index (RSI) exhibited no significant differences (P 0.05) between the test diets except for D4 in which HSI and RSI were significantly lower (P 0.05). Body protein, lipid, ash, energy contents and RNA/DNA ratio were significantly (P 0.05) higher in fish fed with the diet D3 and significantly lower in fish fed with diet D1 compared to fish fed with all other diets. Environmental variables, particularly water temperature and the natural productivity of the pond ecosystem were within the optimum range as required for the growth of deccan mahseer under culture systems.