Measurement of digestibility in agastric fish based on stripping method - apparent nutrient, energy and amino acid digestibilities of common feed ingredients for carp diets (Cyprinus carpio)

Apparent nutrient, energy and amino acid (AA) digestibilities of wheat starch (WS), corn starch (CS), pea protein concentrate (PPC), soy protein concentrate (SPC), corn gluten meal (CGM) and soybean meal (SM) were assessed indirectly in common carp by applying the marker-based indicator method. Each test diet consisted of 70% reference diet and 30% test ingredient. Stripping as faeces collection technique was applied to obtain faecal material two times a day for 9 weeks. Apparent digestibilities of ingredients (ADIs) for crude protein (CP) were higher in SM (79.5 +/- 5.1%) and SPC (75.2 +/- 4.8%) than in CGM (59.2 +/- 6.6%). Regarding ADIs of individual AAs, SM and SPC always showed higher values than CGM and PPC. ADIs for crude carbohydrates in CS (90.4 +/- 2.2%), WS (88.8 +/- 2.0%) and CGM (82.3 +/- 3.9%) exhibited higher amounts than in SM (26.3 +/- 1.0%). Evaluated apparent digestibilities indicate that in particular SM and SPC are good protein and CGM, WS and CS are promising carbohydrate sources to be included in diets for common carp. A strong correlation between ADICP and ADIAA was determined. Stripping used for digestibility measurement in carp was found to be a viable method as conventional passive faeces collecting techniques such as sedimentation or sieving.