Effects of Fecal Collection Methods on Estimation of Digestibility of Protein Feedstuffs by Winter Flounder

Abstract

An accurate method for estimating digestibility of nutrients is essential when developing diets suitable for aquaculture species. Two methods of fecal collection (stripping and sedimentation) were evaluated for estimating crude protein and gross energy digestibility of three protein sources by juvenile (159 ± 8.48 g) winter flounder Pleuronectes americanus in a 3 × 2 factorial design experiment (protein × method) with three replicates of each diet. Fish meal (FM), canola protein concentrate (CPC), and soybean meal (SBM) were the three protein sources and were each included as 15% of a marine fish diet. Chromic oxide (0.5% of dry matter) was added as an inert marker. Crude protein digestibilities determined for stripped feces were significantly higher (P < 0.05) than for feces collected by sedimentation. Gross energy digestibilities based upon stripped fish were also higher (P < 0.05) than those from the sedimentation method. No significant differences in digestibility occurred among the diets containing the different protein sources (P < 0.05). Crude protein and gross energy digestibility in FM, CPC, and SBM were similar. The difference in digestibility using different fecal collection methods might be the result of uneven movement of chromic oxide through the digestive tract.