Incorporation of soybean meal and hazelnut meal in diets for Black Sea turbot (Scophthaimus maeoticus)

The effects of soybean and hazelnut meals as partial replacements of fishmeal were studied in Black Sea turbot (Scophthalmus maeoticus). Juvenile fish (mean 26 g) were fed six isoenergetic (19.1 +/- 0.18 kJ/g diet) and isonitrogenous (511 +/- 0.48 g protein/kg diet) diets for 60 days. The control diet contained fishmeal as the sole protein source. In two of the six experimental diets, soybean meal replaced 20% and 35% of the fishmeal. The other three diets contained 65% fishmeal plus soybean and hazelnut meal at ratios of 25/10, 15/20, 5/30. There was no significant difference (p<0.05) in growth performance between the groups fed the diet containing 20% soybean meal and those fed the control diet. Fish fed the 10% or 20% hazelnut meal diets had similar results as fish fed the diet containing 35% soybean meal. Growth performance, feed utilization, protein efficiency, and nitrogen retention were significantly lower in the group fed the 30% hazelnut diet. Total nitrogen excretion and retention were similar in all groups except the 30% hazelnut group. Results indicate that soybean meal can replace up to 20% of the fishmeal without causing reduction in growth performance, nutrient utilization, or nitrogen retention and that hazelnut meal can be incorporated with 20%, but not 35%, soybean meal at a level of no more than 20% of the diet.