Physicochemical characteristics of dietary fibers may modulate digesta transit behavior. The present study was conducted to clarify the effect of level and particle size (PS) of insoluble fibers on digesta mean retention time (MRT) in the proximal gastrointestinal tract (mouth-ileocecal junction). Six ileal-cannulated pigs (26.8 ± 2.08 kg) were assigned to 3 dietary treatments in a 3 × 3 replicated Latin-square design. Finely ground (1 mm screen) or coarse (intact) oat husks (OH) and soybean hulls (SBH) were added (50:50, w/w) to a maize-whey protein-wheat-based diet at 50 (low) or 250 g/kg (high) inclusion levels to obtain a low-fine fiber (LF), high-fine fiber (HF), and high-coarse fiber (HC) diet. Markers to follow liquids (Co-EDTA), fine solids (Y3O2), or fibrous particles (Yb-mordanted OH and Cr-mordanted SBH) were given as a single pulse dose and marker concentrations were subsequently measured hourly in digesta for 13 h after administration. Mean retention time values were obtained from the concentration of markers in digesta observed over time by fitting a generalized Michaelis-Menten equation and calculating the time of peak. Fiber addition and fiber particle size neither affected the MRT of liquid nor solid digesta phases (P = 0.903). Segregation between solid and liquid digesta phases was observed for all diets (P < 0.0001), although the extent of segregation was greater for LF compared with HF and HC (P = 0.0220). The MRT of SBH particles, but not of OH-particles was longer for coarse vs fine PS (96 min, P < 0.05). In conclusion, digesta MRT was influenced by the dietary concentration but not by PS of insoluble fibers. The addition of insoluble fibers reduces digesta phase segregation from mouth to distal ileum in growing pigs.
Keywords: cannulated pigs; markers; mean retention time; mordants, oat husks; soybean hulls.
The velocity with which feed passes through the gastrointestinal tract affects the processes of digestion and absorption of nutrients. There is evidence that the presence of insoluble fibers, as well as their physical and chemical characteristics, can modify digesta transit. A better understanding of the impact of insoluble fibers on digestive processes may lead to better feeding strategies for pigs. In this study, we investigated the effect of addition of insoluble fibers, and their particle size, on digesta transit behavior from ingestion to the end of the small intestine of growing pigs. The results showed that there is less segregation between solid and liquid digesta phases when adding fibers, regardless their particle size. Changes in digesta transit behavior mean that the kinetics of digestion and absorption of nutrients, and consequently, the metabolic use of the nutrients absorbed may be altered.
© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.