In aquaculture, the evaluation of feed ingredients is essential for the development of high quality aquafeeds. The determination of nutrient digestibility is the first step in evaluating the potential of an ingredient for use in the diet of an aquaculture species. This information is very useful for formulation of diets that maximize the growth of fish, by providing appropriate amounts of available nutrients, but also to limit fish waste products.
Over the last decades, apparent digestibility coefficients (ADC) of dry matter, crude protein, crude lipid, gross energy and phosphorus of different ingredients have been determined for different aquaculture species. However, different methods of feces collection ( dissection, stripping or sedimentation) and different inert markers (c hromic oxides, celites or yttrium) have been used, which often makes it difficult to compare results. Moreover, there is a lack of information on the ADC of ingredient in emerging aquaculture species. To our knowledge, n o reports are available for the ADC of nutrients in pikeperch (Sander lucioperca) . The objective of this work was to validate feces collection by sedimentation for the determination of ADC in macronutrients and phosphorus in pikeperch using yttrium as inert market.
Material and methods
The tria ls were conducted in a recirculating aquaculture system (RAS) consisting of 12 circular tanks (750-L/tank), a drum filter, moving bed filter, UV filter and an oxygen tower. Each tank was connected to a 200-L se ttler for feces collection .
A practical diet , 52% crude protein, 17% crude fat, 20.5 MJ/kg gross energy and 0.02% Yttrium (Y2O3) as inert market, was used in two trials. In the first trial, fifty p ikeperch (b ody weight: 109 ± 9.8 g ) were stocked on each tank for ADC determination. For three weeks, p ikeperch were fed once a day until apparent satiation. The feces were collected after 18 hours, in cold plastic tubes connected to the bottom of the settlers, and stored at -20°C until analysis . The feed and the feces were analyzed for proximal composition of macronutrients, phosphorus and yttrium. The ADC was calculated using the formulas described by
In the second trial, feces collection using three different strategies was determined. 1 ) one feeding per day- feces collection after 18 hours; 2) one feeding per day -feces collection after 21 hours; 3) two feedings per day-two feces collection: after 6 hours and after 18hours. The percentage of feces recovery; feces production and dry weight of feces were determined.
The results of both trials will be presented and discussed during the EAS2023 percid session.
Glencross BD, Booth M, & Allan GL. (2007). A feed is only as good as its ingredients – a review of ingredient evaluation strategies for aquaculture feeds. Aquaculture nutrition, 13, 17-34.