Relationships between glycaemic index and digesta passage of cereal-based diets in pigs

Changes in the rate of passage of digesta may affect feed digestibility and glycaemia, but at the same time glycaemia may also regulate stomach emptying and as a consequence digesta passage rate. The correlations between the glycaemic index (GI) of 12 cereals, the ileal and total tract, dry matter (DM) and organic matter (OM) digestibilities and the ileal digesta flow characteristics of pig feeds containing them were studied. GI for each cereal was calculated as the maximal glucose release rate per minute using an in vitro digestibility system. Pigs fitted with an ileal T-cannula were used to measure the DM and OM digestibilities (ileal and total tract) of the corresponding cereal-based diets, and their ileal digesta flow rate, lag time to initial flow of digesta (T_lag) and mean retention time (MRT). Titanium dioxide (TiO₂) was used as indigestible marker. The Spearman's correlations between the GI, the parameters of digesta flow and the digestibility values were estimated. GI was significantly correlated with ileal digestibility of OM (r=0.58; P<0.05), ileal digesta flow rate (r=0.79; P<0.01), T_lag (r=-0.76; P<0.01) and MRT (r=-0.87; P<0.01). DM and OM ileal digestibility and the digesta flow parameters were also correlated (P<0.05). Positive significant correlations between cereal GI, feed digestibility and digesta flow rate have been found.