Effects of Replacement of Fishmeal with Hazelnut Meal on Growth Performance, Body Composition, and Nutrient Digestibility Coefficients in Rainbow Trout, Oncorhynchus mykiss

Abstract

Hazelnut meal was evaluated as an alternative protein source to fishmeal in diets for rainbow trout, Oncorhynchus mykiss (initial wt 57.5±0.1 g). Hazelnut meal was incorporated in the diet at levels of 0% (control), 7.5%, 15%, 22.5%, and 30%. Diets were tested in triplicate for ten weeks. Higher levels of hazelnut meal produced better growth performance, that was sig- nificantly higher in fish fed 30% hazelnut meal than in the control (p<0.05). Feed utilization and protein efficiency ratios followed a similar trend while the level of hazelnut meal did not significantly affect whole body composi- tion. Apparent digestibility of dry matter and energy of fish fed hazelnut meal at all levels was significantly lower than in fish fed the control (p<0.05). Crude and digestible protein, as well as energy retention, were significant- ly correlated with hazelnut meal level. Nevertheless, energy retention declined in fish fed 30% hazelnut meal. Based on growth performance and nutrient retention, the optimal level of hazelnut meal in diets for rainbow trout may be around 30%.