Growth, Nutrient Utilization, and Digestibility of Mirror Carp (Cyprinus carpio) Fed Diets Containing Graded Levels of Hazelnut Meal in Place of Fishmeal

Hazelnut meal was evaluated as an alternative protein source to fishmeal in diets for mirror carp, Cyprinus carpio (mean initial weight 18.24 +/- 0.08 g). Hazelnut meal was incorporated into diets at levels of 0 (control), 10%, 20%, 30%, or 40%. Diets were tested in triplicate for 12 weeks. Hazelnut meal beyond 10% significantly reduced growth performance in comparison to the control (p<0.05). Feed conversion and protein efficiency ratios were significantly lower in fish fed hazelnut meal higher than 20% (p<0.05). The feed intake, condition factor, and dress-out percentage were not affected by treatment but the viscero-somatic index significantly dropped in fish fed 40% hazelnut meal. High levels of hazelnut meal reduced body moisture and ash but increased lipid concentration. Apparent digestibility coefficients of dry matter and energy were lowest in the diet containing the highest level of hazelnut meal (p<0.05) but those of protein and lipid did not differ. Crude and digestible protein retention were significantly depressed at high hazelnut meal levels. Results suggest that up to 10% hazelnut meal can be incorporated in diets for young mirror carp without growth retardation.