Single and combined effects of chicory (Chicory Intybus) and St John's-wort (Hypericum Perforatum) on growth performance and digestive enzymes activity of Oncorhynchus mykiss

Introduction &

In recent years, the use of medicinal plants has been considered to improve growth and immune system indices of fish. Therefore, the present study was carried out to investigate the single and combined effects of Chicory and St John's-wort hydro-alcoholic extracts on growth indices and digestive enzymes activity of rainbow trout (Oncorhynchus mykiss).

For this purpose, 720 fish with an average body weight of 100±5 g were randomly allocated to four distinct treatments including a control group, 3% chicory extract, 3% St John's-wort extract and a combined treatment containing 1.5% chicory and 1.5% St John's-wort extract. The experiments lasted for 12 weeks and growth indices (final weight, food conversion rate, specific growth rate, weight gain, condition factor and hepatosomatic index) and digestive enzymes activity (lipase, amylase and protease) were measured.

The highest and lowest weight gain, specific growth rate and hepatosomatic index were observed in 3% extract of chicory and 3% St John's-wort extract, respectively (p>0.05). Also, the lowest food conversion ratio and the highest condition factor belonged to group received diet supplemented with 3% chicory (p>0.05). The highest amylase and protease activity were observed in 3% chicory treatment (p<0.05). In addition, the highest and lowest lipase activity was observed in 3% chicory and combined treatment, respectively, however they did not significantly differ (p>0.05).

dietary inclusion of 3% chicory extract would improve the growth indices and digestive enzymes activity of rainbow trout.