Aqua 2018, #We R Aquaculture. 25-29 August. Oral presentation, Montpellier, France
A variety of microalgae species have been studied as replacements for fish meal or fish oil in feeds for Atlantic salmon (Salmo salar). The quality of feed ingredients is often assessed based on their nutrient composition and potential to support fish growth. Their effects on fish health and product quality are also important. Intestinal mucus and mucins play vital roles in protection of fish. Mucins, the glycoproteins responsible for viscoelastic properties and functions of mucus, are produced and secreted by specialized cells. We hypothesize that differently processed microalgae may affect the intestinal health of salmon.
We examined the effect of pre-extrusion processing of two microalgae on growth and health of Atlantic salmon. The fish were fed one of the following five diets for nine weeks: (1) CO: a fish meal-based control (basal) diet, (2) NU: a Nannochloropsis diet, (3) NE: a pre-extruded Nannochloropsis diet, (4) TU: a Tetraselmis diet, and (5) TE: a pre-extruded Tetraselmis diet. The pre-extruded or untreated microalgae were included at 30% in the respective diets.
The weight gain of the fish ranged from 128.5 g to 153.3 g. The final weight of the fish fed the control diet was significantly higher compared to the fish fed diets other than the pre-extruded Nannochloropsis diet (NE). Pre-extrusion of Nannochloropsis tended to have a positive effect on fish growth compared to the other algae-fed fish groups (Figure 1). Pre-extrusion of Tetraselmis significantly improved the antioxidant response based on the higher expression of the related genes in the liver. Further information on the intestinal health including histology and the expression of mucin genes will be presented