Nutrient digestibility in Atlantic salmon and broiler chickens related to viscosity and non-starch polysaccharide content in different soyabean products

Total tract digestibility in Atlantic salmon and ileal digestibility in chi cken were assessed from diets with different soyabean products (hulled, toa sted, extracted, SBM; reduced oligosaccharide content, ROM; ethanol-extract ed protein concentrate, SPC; isolated protein, ISP). The concentration of d ietary fibre was highest in SBM and ROM, while it was low in ISP. In vitro viscosity was also higher in SBM than in the other soyabean products. The d iets for the salmon and chickens were based on the same feed ingredients, w ith the exception that fish meal provided half the crude protein in the sal mon diets, For each species, the diets were isonitrogenous, contained simil ar amounts of fat (fish oil), and were balanced with dextrin, thus substitu ting soyabean non-starch polysaccharides (NSP) and other non-proteinous com ponents by dextrin. In the salmon, total tract digestibility of nitrogen and dry matter were lo wer (p < 0.05) with the SBM and ROM diets than with the ISP diet. In the ch ickens, ileal digestibility of dry matter differed among all treatments (p < 0.05). Digestibility of nitrogen, starch, phosphorus and calcium in the c hickens was lower (p < 0.05) with the SBM diet than with the ISP and SPC di ets, and fat digestibility was lower (p < 0.05) with the SBM and ROM diets than with the SPC diet. Also, the SBM diet gave lower (p < 0.05) digestibil ity of nitrogen, phosphorus and calcium than the ROM diet, while the ROM di ets gave lower (p < 0.05) digestibilities of nitrogen, fat and starch than the ISP and SPC diets. Intestinal viscosity was higher (p < 0.05) and chole sterol content in the blood was lower (p < 0.05) for the chickens fed the S BM-based diet than those fed the other diets. There was a similar response to the different soy products in salmon and chickens with regard to digesti bility of nitrogen and fat (p < 0.05). The negative effects of soyabean mea ls with a low: protein content could indicate antinutritive effects of NSP fractions in soyabean meal, as indicated by the elevated viscosity and the decrease in blood cholesterol content. (C) 1999 Elsevier Science B.V. All r ights reserved.