Abstract:
9A Substituting the fish oil component of aquaculture diets with canola oils: influence of oil grade on its value to a marine fish B.D. Glencross1, J. Curnow1 and W. Hawkins2 1 2 Mariculture Research and Advisory Group, Fisheries Western Australia, PO Box 20, Nor th Beach 6020 WA Pulse and Oilseeds Program, Agriculture Western Australia, Baron_Hay Cour t, South Perth 6151 WA bglencross@fish.wa.gov.au The need for dietary oil in aquaculture feeds has seen considerable use of fish oil, the aquaculture industry now being the world's largest user of this finite resource (Glencross 2000). Several possible alternatives have been identified for salmonids, one being canola oil (Thomassen and Rosjo 1989) but there is little information on either their suitability for use in diets for marine fish or the influence that the processing grade of the oil has on its nutritional value. We examined the influence of progressively diluting the fish oil content of a diet for juvenile red seabream (Pagrus auratus) with either refined or crude canola oils at replacement increments of 25%. Additional treatments included a negative control, where all of the added oil was replaced with inert dietary filler, and a positive control diet with additional fish oil to demonstrate the utilisation of the oil components of the test diets. Feed intake and growth were monitored over an eight_week period. There was no deterioration in performance with the use of refined canola oil whether it replaced some or all of the fish oil. The crude expeller extracted oil reduced growth and feed intake when substituted for more than 75% of the fish oil in the feed. That the growth of the fish fed the diet with 100% of the added oil as crude canola was slightly less than that of the negative control suggests that this inclusion level introduced some anti_nutritional factor(s). These results indicate that both refined and crude canola oils have potential for the replacement of fish oil in diets for marine fish. Glencross, B.D. (2000). Essential fatty acid and lipid requirements of farmed aquatic animals -- sourcing the good oils. Proceedings of the Nutrition Society of Australia 24, 216_224. Thomassen, M.S. and Rosjo, C. (1989). Different fats in feed for Salmon: influence on sensory parameters, growth rate and fatty acids in muscle and heart. Aquaculture 79, 129_135. Table 1 Growth over eight weeks of red seabream on diets with canola oils replacing fish oil. Replacement level Negative control Positive control Baseline Refined canola 0% 25% 50% 75% 100% Crude canola 25% 50% 75% 100% Pooled SEM LSD (P = 0.05) Initial weight (g) 28.4 28.5 28.2 28.5 28.6 28.3 28.3 28.3 28.7 28.3 28.6 0.08 NS Final weight (g) 89.3 100.6 94.8 97.8 95.0 92.4 96.6 95.2 98.0 93.7 87.6 0.77 6.31 Growth Index (%/d) 3.02 3.40 3.23 3.30 3.20 3.14 3.28 3.23 3.29 3.18 2.94 0.03 0.173 Voluntary feed intake (g/d/fish) 1.55 1.20 1.33 1.46 1.42 1.30 1.47 1.33 1.41 1.48 1.30 0.02 0.099 FCR (g/g) 1.19 0.7 0.9 0.99 1.01 0.96 1.01 0.93 0.96 1.07 1.04 0.02 0.083 Recent Advances in Animal Nutrition in Australia, Volume 13 (2001)
