An Animal Model to Study Digesta Passage in Different Compartments of the Gastro-Intestinal Tract (GIT) as Affected by Dietary Composition

An animal model was developed which allows the testing of the effect of dietary factors on digesta passage in the stomach, the small intestine, the large intestine and the total gastrointestinal tract in growing pigs (46 - 119 kg BW). Rates of digesta passage were determined using a simultaneous pulse dose of titanium dioxide (TiO2) mixed in the diet and suspensions of chromiumIIIoxide (Cr2O3) and barium sulphate (BaSO4) in saline, introduced via cannulae to the proximal jejunum and to the terminal ileum, respectively. Faecal recovery of each of the markers was quantified using an one-compartment model from which the transit times (TT) of the markers were derived. The TT of TiO2 represented the passage of digesta over whole gastro-intestinal tract (GIT) whereas the TT of Cr2O3 and BaSO4 represented the TT over the small plus large intestines and over the large intestines, respectively. The TT over the stomach and small intestine were estimated from the TT determined over the whole GIT and over the two sections of the GIT. Besides a control diet (C diet), three diets were offered differing in the contents of non starch polysaccharides (NSP) and water-holding capacity (WHC). A combination of palm kernel expeller and toasted soy bean hulls were included in the diet as NSP sources (NSP diet) and hydrolysed maize starch was included to elevate WHC (WHC diet). The fourth diet had both a high NSP content and a high WHC content (NSP plus WHC diet). The mean transit time (MTT) of the marker passing the whole GIT was on average 75 h and NSP significantly decreased TT over the total GIT and through the large intestines (P < 0.05). In contrast, NSP tended to increase the TT of the stomach contents (P < 0.10). The effects of WHC were smaller and limited to tendencies for a decrease of the TT in the large intestines (P < 0.10) and an increase of the TT in the small intestine (P < 0.10). It is concluded that NSP and to a lesser extent WHC, have opposite effects on digesta passage in the proximal and distal GIT, respectively. The animal model developed in the present study seems a valuable method to test the effect of dietary factors on the passage of digesta.