Effects of soybean hulls and lignocellulose on performance, nutrient digestibility, microbial metabolites and immune response in piglets.

A feeding trial with 96 piglets was performed to investigate the effect of added soluble (SDF) and insoluble dietary fibre (IDF) sources on performance, apparent total tract digestibility (ATTD), concentration of microbial metabolites and pro-inflammatory marker genes as indicators for immune response. Piglets were allotted to four treatments (T): T1 control, T2 with soybean hulls (IDF/SDF: 8.35) and T3 and T4 with two different kinds of lignocellulose (IDF/SDF: >70). Diets were isofibrous for their value of total dietary fibre to underline the particular physicochemical properties of fibre sources. No differences were observed regarding average daily feed intake, average daily gain (ADG), feed conversion ratio and body weight, while T2 expressed higher ADG in the grower phase (day 14-54) vs. T3. Soybean hulls (T2) resulted in higher ATTD of dry matter and organic matter vs. T4; ether extract vs. T1 and neutral detergent fibre vs. T1, T2 and T3. The concentration of short chain fatty acids did not differ among treatments. Ileal digesta in T2 generated higher amounts of cadaverine vs. T3 and T4, likewise T1 vs. T4. Finally, no impact on immune response was detected. In conclusion, soybean hulls affected ATTD positively and lignocellulose prevented the formation of cadaverine, no overall direct response of SDF nor of IDF for the inclusion level  were observed.