Investigation of growth performance, carcass indices, fillet chemical composition and non-specific immune parameters of Rainbow trout (Oncorhynchus mykiss) fed diets containing poultry by-product meal supplemented with canola meal and cottonseed meal

Abstract

In the present study four isonitrogenous (40% crude protein) and isocaloric (3600 kcal/kg digestible energy) diets were formulate. Control diet was based on fish meal (FM), diet 2 (PFM) contained 25/34% poultry by-product meal and 24/66% fish meal, diet 3 (CPFM) contained 16/14% fish meal, 25/34% poultry by-product meal and 10% cottonseed meal and diet 4 (CCP) was free from fish meal and had 40/24% poultry by-product meal, 10% cottonseed meal and 7/8% canola meal to meet the nutritional requirements of rainbow trout weighing 150±9 grams for a period of three months in order to determine their effects on growth performance, carcass indices, fillet chemical composition and non-specific immune response of rainbow trout. The results of this experiment showed that weight gain, feed intake and body condition score were not affected by the proposed diet formulation, but a significant improvement was observed in feed conversion ratio and specific growth rate (P<0.05). Furthermore, it was indicated that lysozyme level and immunoglobulin had no change, but anti-trypsin activity associated with alpha-anti-protease of the fish fed (CCP) was significantly lower (P<0.05). Total antiprotease activity of the fish fed (CPFM) and (CCP) was also lower compared with the control diet (p<0.05). We can conclude that with increasing the plant protein levels, a significant reduction in serum total protein in all treatments compared to the control group was observed (P<0.05). Poultry by-product meal supplemented with cottonseed meal and canola meal used in this study, which has been replaced fish meal up to 100%, resulted in a reduction of non-specific immune parameters, but had no adverse effect on growth performance, carcass indexes and carcass chemical composition.