Incorporation of Rapa Whelk (Rapana venosa) meal in diets for rainbow trout (Oncorhynchus mykiss) fry

Abstract

The purpose of this study was to investigate the effects of partial fishmeal replacement with Rapana venosa meal in diets for rainbow trout (Oncorhynchus mykiss) fry. In the trial, fish (1.03 ± 0.01 g) were fed diets replacing fishmeal with Rapa whelk meal at the following levels: 0 g/kg (CD), 50 g/kg (D-5), 100 g/kg (D-10) or 150 g/kg (D-15) for 67 days. At the end of the experiment, fish fed diet with 50 g/kg Rapa whelk meal inclusion showed similar growth performance to those fed the control diet. Feed intake, feed conversion ratio (FCR) and growth performance of fish were inversely affected with increasing levels of dietary inclusion of Rapa whelk meal, excluding the 50 g/kg fish meal replacement treatment. Survival rates, hepatosomatic indices and total essential amino acid levels were similar in all experimental groups. The viscerosomatic index, crude fat and dry matter decreased in fish fed the Rapa whelk meal-incorporated diets. A decreasing presence of PUFA was observed as Rapa whelk meal inclusion increased in diets. Rapa whelk meal enhanced trypsin activity when used at 50 g/kg in diet, however decreased the activity at 100 g/kg and above ratios. To conclude, Rapa whelk meal can replace fishmeal at 50 g/kg in rainbow trout diets without causing a negative impact on growth, survival, chemical composition and digestive enzyme activities.