Aqua 2018, #We R Aquaculture. 25-29 August. Oral presentation, Montpellier, France
Supplying quality protein and lipids for Atlantic salmon feeds is a challenge. Fishmeal and fish oil in present-day salmon feeds are to a large extent replaced with plant-derived ingredients. Nutritional requirements of salmonids cannot be met solely from plant-derived ingredients. There is thus a need for more reliable, scalable and sustainable protein and oil sources with good nutrient profiles. Microalgae are promising alternative sources, and their production is expected to grow to supply the feed ingredient market. We have observed that nutrient digestibility values of microalgae-included feeds were lower compared to the reference feeds in Atlantic salmon (Gong et al. 2018). In the present study we investigated the potential of feed additives in stimulating the digestive system, to improve the utilization of the nutrients in the microalga Nannochloropsis sp.
Four diets were formulated; control diet without the microalga Nannochloropsis sp. (CT), a diet containing 10% of the microalga (NC), and two diets (NZ and ND) containing 10% of the microalga and two different commercial feed additives. Fish (initial av. weight 227 g) were fed the experimental diets for 10 weeks. Feed consumption was monitored daily. At the end of the feeding period, fish weights were recorded before collecting the samples of interest; distal intestine, fillet, whole body and faeces of fish. Growth, survival, gut morphology, digestibility, and quality of fish and fillets were assessed to understand the effect of the experimental diets.
The specific growth rate and feed conversion ratio of the fish did not suggest any positive influence of the additives. Although the viscerosomatic indices of the study groups were not different, hepatosomatic index of the ND-fed fish was significantly higher compared to the NC-fed fish. Samples are currently being analyzed and results from the work will be presented at the conference.