Fermentation Characteristics and In Vitro Digestibility of Fibers and Fiber-Rich Byproducts Used for the Feeding of Pigs

SIMPLE SUMMARY: Inclusion of dietary fibers into the diet may have positive impact on health and wellbeing of pigs. The objective of the study was to examine physicochemical properties of fiber preparations and fiber-rich byproducts in relation to fermentability and digestibility using in vitro batch-culture incubation. Powdered cellulose, Aspergillus niger mycelium, which is a byproduct of citric acid production, lucerne chaff, soybean shells, wheat bran, and sugar beet pulp were notably fermented and contributed to the digestible dry matter and organic matter when used as diet constituents. The tested lignocelluloses were not fermented and are rather useful as bulk materials. ABSTRACT: Dietary fibers may have positive impact on health and wellbeing of pigs. The study examined physicochemical properties of two lignocelluloses (including and excluding bark), powdered cellulose, Aspergillus niger mycelium, lucerne chaff, soybean shells, wheat bran, and sugar beet pulp in relation to fermentability and digestibility using in vitro batch-culture incubation. Maize starch and a purified cellulose were used as standardized substrates for classification of the test substrates. The substrates covered a wide range regarding their physicochemical properties. Swelling capacity (SC) was 9–411%, water binding capacity (WBC) was 4.4–14.3 g/g dry matter (DM), and water holding capacity (WHC) was 4.1–10.6 g/g DM. Gas production and other fermentation parameters—namely post-incubation pH, CH(4), NH(3), and short chain fatty acids (SCFA) concentrations—revealed a significant fermentation of sugar beet pulp, soybean shells, lucerne chaff, wheat bran, A. niger mycelium, and powdered cellulose, whereas the lignocelluloses were not fermented. Significant correlations were found between the physicochemical properties and the fermentation parameters (p < 0.05). Enzymatic pre-digestion mostly reduced gas, NH(3), and SCFA production. In vitro digestibility of DM (IVDMD) and organic matter (IVOMD) was mostly negligible after enzymatic pre-digestion. Fermentation alone led to only 0.10–0.15 IVDMD and 0.14–0.15 IVOMD in lignocelluloses and powdered cellulose, respectively, but 0.44–0.37 IVDMD and 0.46–0.38 IVOMD in the remainder of substrates (p < 0.05). In vitro digestibility was again correlated with the physicochemical properties of the substrates and the fermentation parameters (p < 0.05). The fiber preparations and fiber-rich byproducts were fermented to a relevant extent. In contrast, lignocelluloses were not fermented and can be used rather as bulk material.