Effects of diet containing different levels of yeast, Saccharomyces cerevisiae and plant proteins on growth indices, carcass biochemical composition and total intestinal bacteria count in a recirculating aquaculture system for rearing rainbow trout, Oncorhynchus mykiss

Abstract

In this study, several balanced protein diets using plant proteins and yeast, were employed with the aim of reducing the fish meal in the diet. The experimental treatments included: control (T0) as commercial diet, (Faradaneh Co., Iran); treatment 1 (T1) containing 25% fish meal (FM) and 58% plant protein (pp); treatment 2 (T2) containing 23% FM, 4% yeast, 47% pp; treatment 3 (T3: 20% FM, 9% yeast, 52% pp); treatment 4 (T4: 18.5% FM, 14.5% yeast, 46% pp); treatment 5 (T5: 17% FM, 21% yeast, 41% pp); treatment 6 (T6: 10% FM, 25% yeast, 45% pp) and treatment 7 (T7: 28.5% yeast, 45% pp). A total of 160 rainbow trout Oncorhynchus mykiss fingerlings with an average weight of 38 ± 2 were randomly introduced into the 16 experimental tanks and cultured for nine weeks. The results showed that the growth performance of fish such as final weight, specific growth rates and protein efficiency rates increased in T3 in comparison with the other treatments (p<0.05). The highest carcass protein was observed in T3 and the highest fat was observed in the control group. The highest total count intestinal bacteria was observed in treatment 5 and the lowest in control and treatment 2 (p<0.05). The best experimental diet was recorded in T3. It was found that growing rainbow trout using diets containing vegetable proteins, yeast, without fish meal is possible.

Keywords

• fishmeal
• plant proteins
• yeast
• rainbow trout
• carcass composition
• total bacterial count